Report No. 224

kfi/b 7/

by

K. A. Langeland

Assistant Professor Department of Crop Science

School of Agriculture and Life Sciences Agricultural Research Service

North Carolina State University

March 1986

U N C - WRR I -86- 224

MANAGEMENT PROGRAM

FOR ALLIGATORWEED IN NORTH C A R O L I N A

I<. A. Langeland

Assistant Professor Department of Crop Science

Agricultural Research Service North Carolina State University Ral eigh, North Carol i na 27695

School of Agriculture and Life Sciences

"The research on which the report i s based was financed in part by the United States Departnent of the Interior, Geological Survey, t h r o u g h the North Carolina Water Resources Research Inst i tute . 'I

Two hundred and f i f t y copies of th i s publication were printed a t a cost of $398.10 or $1.59 per copy.

Agreement No. 14-08-0001-G924 WRRI Project No. 70039 USGS Project No. 04

ABSTRACT

A survey t o determine the e x t e n t o f a l l i g a t o r w e e d i n Nor th Caro l ina

revea led 1023 ha o f aquat ic a l l i g a t o r w e e d d i s t r i b u t e d among 32 count ies

and 1042 ha o f t e r r e s t r i a l a l l i g a t o r w e e d d i s t r i b u t e d among 9 count ies .

Major problems caused t o Nor th Caro l ina water resources by the weed a r e

f l o o d i n g and impedance t o nav iga t ion .

b e e t l e s t h a t o r i g i n a t e d from a c o l l e c t i o n i n Southern Argent ina, nor a l -

l i gatorweed f l e a beet1 es c o l l ected from F1 o r i d a , n o r n a t u r a l l y o c c u r r i n g

popu la t ions o f a l l i g a t o r w e e d stemborer exer ted a use fu l l e v e l o f a l -

l i g a t o r w e e d suppression i n Nor th Caro l ina.

t i o n s f o r c o n t r o l l i n g a l l i g a t o r w e e d suggested t h a t a successful a l -

l i g a t o r w e e d management program can be implemented us ing g lyphosate f o r

management i n lakes and r i v e r s and imazapyr f o r n o n - i r r i g a t i o n

di tchbanks.

p r e l i m i n a r y e v a l u a t i o n s and should be u s e f u l i n t h e program pending ex-

pansion o f EPA r e g i s t r a t i o n t o aquat ic s i t e s and di tchbanks.

N e i t h e r a1 1 igatorweed f l e a

Resu l ts o f h e r b i c i d e evalua-

T r y c l o p y r was e f f e c t i v e f o r c o n t r o l 1 i n g a l l i g a t o r w e e d i n

ii

AC KNOW L ED GFlE E.1 TS

Cooperation by county extension personnel, soil conservationists,

and d i s t r i c t f isher ies biologists, without whom the alligatorweed survey

could not have been completed, i s greatly appreciated. Special ap-

preciation i s expressed t o James W. (Pete) Kornegay and Lacy E. Nichols

f o r the time t h a t was necessary t o report the extensive alligatorweed in

Distr ic t 1 and District 4. Special appreciation i s also expressed t o

Lewis W. Smith , William R. Jes ter 111, Philip A. H igh t and Stan Winslow

of the North Carolina Agricultural Extension Service and Rufus Croom of

the Soi l Conservation Service for their assistance i n locating "On Farm

Test Sites" for herbicide evaluation. Thanks to Tom Tucker and John

Warner for their assistance i n herbicide applications, and t o Maria

Pal 1 o t ta for typing the manuscript.

Pa r t of the herbicides used in this study were provided by American

Cyanami d Company, Dupont Chemical Company , El anco Products Company , J L B

and Associates, Flonsanto Chemical Company, Union Carbide Agricultural

Products, and Vel sic01 Company.

Financial s u p p o r t for the work was provided i n p a r t by the North

Carolina Agricultural Research Service, North Carol ina Agricultural Ex-

tension Service, and a g r a n t from the U.S. Department of Inter ior ,

Washington, D . C . , th rough The University of North Carolina Water

Resources Research Inst i tute .

DISCLAIMER STATEMENT

Contents of this publication do n o t necessarily re f lec t the views

and policies of the Water Resources Research Ins t i tu te nor does mention

of trade names o r commercial products consti tute the i r endorsement o r

recommendation for use by the Inst i tute o r the State of North Carolina.

TABLE OF CONTENTS

Abs t rac t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . i i i

L i s t o f F igures . . . . . . . . . . . . . . . . . . . . . . . . . v i

Conclusions and Recommendations . . . . . . . . . . . . . . . . . i x

In t roduc t ion . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Mate r i a l s and Methods . . . . . . . . . . . . . . . . . . . . . . 6

V List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . .

Common and Chemical Names of Chemicals Used i n T h i s Report . . . . V i 1

Alligatorweed Survey . . . . . . . . . . . . . . . . . . . . . 6

Bio logica l Suppressants . . . . . . . . . . . . . . . . . . . . 6

F loa t ing Alligatorweed . . . . . . . . . . . . . . . . . . 7

Rooted Alligatorweed . . . . . . . . . . . . . . . . . . . 8

Results and Discussion . . . . . . . . . . . . . . . . . . . . . . 9

7 Herbicide Evalua t ions . . . . . . . . . . . . . . . . . . . .

A1 1 i gatorweed Survey

Biological Suppressants . . . . . . . . . . . . . . . . . . . . 16

Herbicide Evalua t ions . . . . . . . . . . . . . . . . . . . . 18

F loa t ing Alligatorweed . . . . . . . . . . . . . . . . . . 18

Rooted Alligatorweed . . . . . . . . . . . . . . . . . . . 20

L i t e r a t u r e Ci ted . . . . . . . . . . . . . . . . . . . . . . . . . 32

Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

9 . . . . . . . . . . . . . . . . . . . . .

i v

LIST OF TABLES

Page Table 1. Summary of alligatorweed (Alternanthera

phi 1 oxeroi des) occurrence in North Carol i na counties reported by county agricultural extension service offices, soil conservationists, and district f i sheri es bi ol ogi sts during 1984 survey . . . . . . . . . 11

Table 2. Efficacy of glyphosate and fluridone, when applied alone or together, for controlling alligatorweed (Alternanthera philoxeroides) in shallow drainage canals in Washington and Perquimans Counties, N.C.. , . . 21 Efficacy of various rates of glyphosate for con- trol ling alligatorweed (Alternanthera philoxeroides) in shallow drainage canals in Washington and Tyrrell Counties, N.C., when applied in June 1984 or reapplied in October 1984 . . . . . . . . . . . . . . . 25

Table 3.

Table 4. Efficacy of 2,4-0 and dicamba for controlling alli- gatorweed (Alternanthera philoxeroides) in a shallow drainage canal located in Tyrrell County, N.C. when applied in June 1984 . . . . . . . . . . . . . . . . . . 27

Table 5. Efficacy of imazapyr for controlling alligatorweed (Alternanthera philoxeroides) in shallow drainage canals located in Washington, Tyrrell , and Perquimans Counties, N.C. . . . . . . . . . . . . . . . . . . . . . 28

Table 6. Efficacy of several herbicides for control of alli- gatorweed (Alternanthera philoxeroides) in shallow drainage canals located in lilashington County, N.C. . . . 31

V

LIST OF FIGURES

Page - Figure 1. North Carolina counties that reported occurrences

of alligatorweed during 1984 . . . . . . . . . . . . 10

Figure 2. Major alligatorweed infestations reported in North Carol i na rivers, streams, and drai nage canal s in 1984 . . . . . . . . . . . . . . . . . . . . . . . . 14

v i

LIST OF COMMON AND CHEMICAL NAMES OF HERBICIDES USED IN THIS REPORT

Common Name or Designation

ame tryn

amitrole AMS

bromaci 1

dal apon dicamba dichlobenil di uron

endothall erbon

fenac fenuron fenuron TCA fl uridone

glyphosate

hexazinone

i mazapyr

i pazi n

karbutil ate

FIC PA mal ei c hydrazi de metsul furon methyl

monuron

neburon paraquat pic1 oram

s i 1 vex

simazine

Chemical blame

2-ethylamino-4-(isopropylamino)-6- (me thy1 thi o - - s- tr i azi ne

3-amino-s-triazole ammoni um-sul famate

5-bromo-3-sec-butyl-6-methyluracil - 2,2-dichloropropionic acid 3,6-dichloro-o-anisic acid 2,6-dichlorobFnzoni trile 3,(3,4-dichl orophenyl 1-1 ,l-dimethyl urea

7-oxabicyclo[ 2.2.11 heptane-2,3-dicarboxyl ic acid 2- (2,4,5-trichl orophenoxy) ethyl 2.2-dichl oro-

propionate

(2,3,6- trichl orophenyl )acetic acid lYl-dimethyl-2-phenylurea 1 , 1-dimethyl -3-phenyl urea mono( trichl oroacetate) 1-methyl -3-phenyl -5-[3- (tri fl uoromethyl ) phenyl]-

4( H )-pyridi none

- El-( phosphonomethyl glycine

3-cyclohexyl-6-(dimethyl amino)-l-methyl-1,3,5- triazine-2,4( 1H,3H) - - dione

2-[4,5-dihydro-4-methyl-4- (1-methyl ethyl )-5- oxolH-imidazol-2-yl]-3-pyridine- carb5xyl i c aci d

2-chloro-4-(diethylamino)-6-(isopropylamino)- -s-triazine

(m-(3,3-(dimethyl ureidolphenyl tert- -

butyl carbamate)

(4-chl oro-2-methyl phonxyfacetic acid 153-dihydro-3,6-pyridazi nedione methyl 2-[[[[ (4-methoxy-6-nethyl-l,3,5-triazi n-

3 - p-chl orophenyl 1 -1 , 1 dimethyl urea

1-a-butyl -3-(3,4-dichl orophenyl )-1-methyl urea 1,l' -dimethyl -4,4'-bipyridi ni um ion 4-amino-3,5,6-trichloro-l-pyrdinecarboxylic acid

2- (2,4,5-trich'i orophenoxy) propionic acid

2-yl 1 amino]-carbonyl I-amino]-sul fonyl I- benzoate

6-chl oro-N,M'-diethyl-l,3,5-triazi - - ne-l,4-diami ne

v i i

sul fometuron methyl methyl 2-[ [ [ [ ( 4, &dimethyl -2-pyr imi d i nyl ) ami no] carbonyl laminolsul fonyl l -benzoate

TCA t r ic l opyr

2 4-D 2,4,5-T 2,3,6-TBA

t r i c h l o r o a c e t i c ac id (3 , 5 , 6 - t r i c h l oro-1-pyrdi nyl ) oxy1 a c e t i c ac id

( 2,4-di c h l orop henoxy ) ace t i c ac i d ( 2 , 4 , 5 - t r i c h l orophenoxy) a c e t i c ac id 2 , 3 6- tr i chl orobenzoi c a c i d

v i i i

CONCLUSIONS AND RECOllFlENDATIONS

Termination of alligatorweed management i n 1970 has allowed the weed

t o increase seven-fold over a 1963 survey in North Carolina.

abundan t infestations i n the Lumber, Chowan, and Pasquotank basins

seriously impact water resources and agriculture i n North Carolina by

reducing recreational value, causing flooding, and by i n v a d i n g ter-

res t r ia l habitats i n cropland. Based on evaluations of herbicide and

biological suppressants, the following management o f a l l igatorweed i s

recommended:

Locally

1. The North Carolina Department of Natural Resources and Community

Development, Division of Water Resources, which has recently taken the

lead role for implementation of aquatic weed control in the s ta te ,

should expand the Alligatorweed Management Program t h a t was in i t ia ted i n

1984 and described i n th i s report.

other areas in the s t a t e where alligatorweed r e s t r i c t s public use of

water o r i s a potential cause of flooding.

expanded to include creek and canal t r ibutar ies that are nursery grounds

for future alligatorweed infestations of the treated areas. Glyphosate,

a t recommended rates, should be used for alligatorweed management i n

lakes and rivers.

Imazapyr should be used a t a ra te of 0.06 t o 0.12 kg ae/100L on a spray

t o wet basis for alligatorweed management on non-irrigation ditchbanks.

W i t h two consecutive applications, alligatorweed will be essentially

eliminated from some ditches, and reinfestation can only occur by

vegetative reintroduction. The i n i t i a l imp1 ementation will require some

ef for t and expense. However, a f te r alligatorweed i s i n i t i a l l y reduced,

only maintenance control operations will be necessary, t h a t will

The program should be expanded t o

The program should also be

Two applications will be necessary the f i r s t year.

i x

t o keep private

a1 1 i gatorweed.

control 1 i ng the

sal on farm equ

3. Efforts

require, a t most, one annual visi t per s i t e for spot treatments.

2. The North Carolina Agricultural Extension Service should s t r ive

landowners informed of current management practices for

I t should s t ress t o the landowners the importance of

weed when identified on their land and avo id ing disper-

pment such as cult ivators, draglines, and backhoes.

should continue t o develop the most cost-effective her-

bicides for alligatorweed management.

given to better determine the effectiveness of triclopyr for controlling

a l l igatorweed and the potential for developing E P A registration for

aquatic s i t e s for tr iclopyr and imazapyr .

Particular attention should be

4. Efforts should be continued t o develop biological suppressants

t h a t are adaptable t o North Carol i n a ' s climate.

X

INTRODUCTION

Alligatorweed (Alternanthera pkiloxeroides) i s a fast-growing,

herbaceous, warm season, facultative aquatic, perennial plant. I t i s a

Sou th American species that was f i r s t identified in the United States i n

1890.

the southeastern United States , from F1 o r i d a t o Virginia (Gangsted,

1977), and was recognized a s a serious aquatic weed due to i t s ab i l i ty

t o form thick floating mats of vegetation t h a t can severely impede

navigation, reduce water quality, cause flooding, and increase sedimen-

tation rates i n water bodies.

By the 1960's the plant occupied over 160,000 acres of water in

Extensive e f for t s by the United States Department of Agriculture

(USDA) and United States Army Corps of Engineers (USACE) have led t o

suppression of alligatorweed i n i t s southern range using several

biological suppressants. These biological agents include a l l igatorweed

thrips (Amynothrips andersoni) , a1 1 igatorweed stemborer (Vogtia mall o i )

and a1 1 igatorweed flea beetl e (Agasicl es hygrophil a )

tab1 i sh a1 1 i gatorweed f l ea beetl es i n North Carol i na have been

Attempts t o es-

unsuccessful, apparently due t o the insec t ' s cold sensi t ivi ty (USAEC,

WES 1981). The USDA and North Carolina Department of Agriculture are

currently trying t o develop a col d-to1 erant a1 1 igatorweed flea beetl e

which may be effectively established i n North Carolina, b u t as ye t t h i s

has been unsuccessful (Langeland e t a1 , 1984).

Management of alligatorweed w i t h herbicides has been d i f f icu l t . A

large number of herbicides, formulations, and application methods have

been evaluated, primarily the phenoxy herbicides. I t i s widely observed

t h a t phenoxy herbicides give rapid t o p k i l l of alligatorweed b u t fa i l t o

translocate t o the viable apical buds from which regrowth occurs usually

before 5-8 weeks ( Z u r b u r g e t a1 , 1961). This i s an unusual problem con-

sidering the mobility of these materials i n many other plants.

Si1 vex has been relatively effective for control 1 i n g a1 1 igatorweed

in many areas; however, i n North Carolina those resul ts have n o t been

duplicated.

carried o u t i n North Carolina and Sou th Carolina a b o u t 3000 herbicide

treatments were evaluated over a 5-year period. These treatments i n -

cl uded a variety of application methods, car r je rs , and herbicides.

herbicides used included 2,4,5-T, 2,4-0, MCPA, 2(2,4-DP) (dalapon) , s i l -

vex esters and amides, fenac, amitrole and 2,3,6-TBAY TCA, AMs, endothall, simazine, neburon, fenuron, monuron, d i u r o n , monuron TCA,

fenuron TCA and erbon. In a d d i t i o n , treatments included oil/water

car r ie rs , weighted emul sions of silvex and 2,4-D granular applications,

overlay treatments and repeated spraying of new growth w i t h silvex and

2,4-D.

that effective control occurred only when flooding of the treated areas

occurred shortly a f te r herbicide treatment. Silvex, the most consis-

tently effective material eval uated, provided less t h a n 50% control when

applied a s a spray solution.

ceptable control only when the p l a n t was emersed, flowering, and well

rooted. Excellent control was observed when 2,4-D and fenac were ap-

plied in combination 8-10 weeks before f i r s t frost and flooded w i t h 18-

36" of water just a f te r treatment (Steenis 8, PlcGilvrey, 1961).

In a large extended alligatorweed management program

The

Results were e r r a t i c over the evaluation period b u t indicated

Granular applications of silvex gave ac-

In F1 ori da , 78 herbicides were eval uated for a1 1 i gatorweed control

under greenhouse conditions. Of these herbicides, 2,4-D es te r , si1 vex,

s i 1 vex xylene emul sion , d i q u a t , i pazi n , endothall , paraquat , and an ex-

perimental dimethyl urea compound were selected f o r further fie1 d t e s t s

2

on the basis of efficacy. After extensive f ie ld t e s t s , i t was concluded

t h a t only si1 vex and si1 vex xylene emu1 sion suppressed a1 1 igatorweed for

up t o 8 weeks.

ligatorweed pas t 6 weeks.

ning for a l l treatments although silvex treatments provided the best

suppression (Blackburn, 1963).

The remaining treatments failed t o suppress al-

A t 8 weeks regrowth was proceeding o r begin-

Ametryne was evaluated for alligatorweed control i n b o t h the green-

house and f ie ld . Greenhouse studies indicated acceptable control a t 8

weeks.

2,4-D over a 4 m o n t h period reduced alligatorweed growth only 33% a f t e r

6 months and was judged ineffective (Weldon and Blackburn, 1967) .

However, f ie ld t e s t s indicated t h a t 3 applications of ametryne +

In South Carolina several herbicides have been recognized a s i n -

h b i t o r s of alligatorweed growth when applications are followed by

f ooding. These herbicides, which include maleic hydrazide, amitrole,

dalapon, erbon, silvex, MCPA and 2,4-D acetamide, have given 90-100%

control under such flooding conditions, b u t are highly ineffective in

areas not subject t o flooding (Steenis and FdcGilvrey, 1961).

Dichlobenil has been evaluated for a l l igatorweed control i n South

Carolina, Georgia, Florida, and Louisiana. The treatments used involved

several granular applications and fol i a r appl ications w i t h and w i t h o u t

nonphytotoxic o i l s .

mer and winter time periods. The resul ts of the evaluations indicate

that fo l i a r applications of dichlobenil are ineffective regardless of

addition o r deletion of nonphytotoxic o i l s . Granular dichlobenil ap-

plied in summer was ineffective; however, winter applications were ef-

fective when the treated area was drained 2 weeks before treatment and

allowed t o stand 10 weeks a f t e r treatment (Weldon e t a l , 19681.

The granular applications were applied in b o t h sum-

3

Data c o l l e c t e d from e v a l u a t i o n s of 17 herbicide t rea tments show t h a t

on ly silvex + amitrol f o l i a r appl ied l a t e i n the season provided better

than 50% cont ro l 4 months a f t e r t reatment . All o t h e r t rea tments were

less than 30% a t 4 months. Those t rea tments included granular formula-

t i o n s o f silvex, 2,4-D, fenac , sodium a r s e n i t e , and endothal l + 2,4,5-T

and f o l i a r a p p l i c a t i o n s of paraquat , d i q u a t , silvex, picloram, a m i t r o l ,

fenac, fenac + d i q u a t , amitrol + d i q u a t , amitrol + picloram, s i l v e x

PGBEE + amitrol and picloram + s i 1 vex PGEE + ami t r o l (Spencer, 1967).

Other d a t a from South Carol ina i n d i c a t e 90% cont ro l of t e r r e s t r i a l

a l l iga torweed one y e a r af ter t rea tment w i t h k a r b u t i l a t e g r a n u l a r her-

b i c i d e and 90% con t ro l of rooted-emersed a l l iga torweed w i t h s p r i n g ap-

p l i c a t i o n s o f granular d ich lobeni l (Blackburn Durden, 1974).

S i lvex has g e n e r a l l y been cons idered the only c o n s i s t e n t l y effective

h e r b i c i d e f o r a l l iga torweed c o n t r o l . The USACE Wilmington District

began an a l l iga torweed c o n t r o l program i n North Carol ina i n 1960 us ing

s i l v e x a s the primary herb ic ide . In 1970 this program was stopped due

t o concern over environmental and h e a l t h impacts o f silvex and because

a l l iga torweed was no longer occurr ing a t problem levels1.

resul t of pub1 i c concern over possi bl e environmental and heal t h risks , the E P A i n i t i a t e d a c t i o n s t o suspend the use o f S i l v e x and i n 1983

banned a l l uses of the mater ia l (Gangstad, 1984).

In 1979, a s a

During the e a r l y 1980 ' s the North Carol ina Agr icu l tura l Extension

Serv ice began rece iv ing many r e q u e s t s f o r information on how t o c o n t r o l

lEnvironmenta1

o f 1965). United

1984.

assessment, Aquatic PI a n t Control Program (Rett Act

S t a t e s Amy Corps o f Engineers, Wilmington District.

4

of problems caused by

vers. Glyphosate, wh

use, was recommended,

alligatorweed and widespread reports

drainage canals, lakes, ponds, and P

recently been registered for aquatic

the plant i n

eh had

b u t many com-

plaints were received indicating t h a t unsatisfactory control resulted.

In response t o these complaints the North Carolina State University Crop

Science Department began, in 1983, evaluating newly introduced her-

bicides for alligatorweed control i n order t o develop better

recommendations.

publicly owned waters, questions arose over renewal of federal assis-

tance for alligatorweed management.

thorough survey should be conducted i n order t o document the extent and

nature of problems t h a t were being caused by alligatorweed.

presents data from three years of testing herbicides f o r alligatorweed

control i n North Carolina and data from a survey of alligatorweed in

North Carolina in 1984, and i t recommends actions t o be taken based on

these data.

Since many o f the alligatorweed problems originated in

I t was therefore decided that a

This report

5

MATERIALS AND METHODS

A1 1 i gatorweed Survey

Questionnaires (Appendix) were mailed t o county extension chairmen,

d i s t r i c t f isher ies biologists, and soil conservationists representing

all North Carolina counties t o the east of the western boundaries of

Scotland, Hoke, Harnett, Wake, Durham, and Granville Counties requesting

information related t o the occurrence, location or problems caused by

a l l igatorweed. In general , county extension personnel, f isher ies

biologists, and soil conservationists cooperated so t h a t extension per-

sonnel and soil conservationists reported on a g r i c u l t u r a l ly re1 ated

occurrences, and f isheries biologists reported on occurrences i n creeks,

r ivers, lakes, and other public waters. This allowed cooperators t o

report w i t h i n the i r own areas of experti se and m i n i m i zed redundancies.

Occurrences i n three counties n o t included i n the survey area were re-

corded from routine weed identifications and recommendations conducted

by the project leader.

question, sight inspections were made, i f possible, by the principal

investigator.

these values were converted t o metric values and rounded t o the nearest

who1 e number.

When identification o r area estimates were i n

Estimable areas of infestation were reported i n acres and

B i ol ogical Suppressants

Alligatorweed flea beetles t h a t were reared from genetic stock col-

lected from colder extremes of the organism's natural range i n Argentina

(Buckingham and Boucias, 1982) were obtained from the USDA Ouarantine

1 a b i n Gai nesvill e , F1 o r i da. Three hundred adul t insects were re1 eased

6

on August 19, 1983 a t a 0.5 ha pond in Salemburg, North Carolina t h a t

was 33% covered by alligatorweed mats.

release o f six hundred adult insects was made a t t h i s s i t e and a release

was made a t a 0.25 ha , 100% covered pond i n Penderlea (Pender County),

North Carolina.

beetles were obtained from the United States Army Corps of Engineers,

Jacksonville Distr ic t , on June 7, 1984 and released i n the Thirty-foot

Canal (Washington County, North Carolina) A1 7 releases were conducted

according to United States Army Engineers Waterways Experiment S t a t i o n

guidelines (USAEWES, 1981). All these s i t e s were monitored routinely

for presence of the beetles and damage caused t o the alligatorweed

dur ing the year o f release and the following spring.

September 1, 1983 a second

Nine thousand Florida-collected a l l igatorweed flea

Herbi c i de Eva1 u a t i on

F l o a t i n g A l l igatorweed

Two and a half ha of alligatorweed i n the Scuppernong River between

the County Road 1155 bridge and the Uashington/Tyrrell County l ine were

treated w i t h a tank m i x containing 0.60 kg ae glyphosate per l O O L , 0.5%

non-ionic surfactant and 0.075% poly-acrylamide copolymer on August 6 ,

7, and 9 , 1984. The foliage was sprayed t o wet u s i n g a handgun w i t h a

D-8 nozzle. Reapplication was made October 18, 1984. This exercise was

conducted to demonstrate, on a large scale, the effectiveness of this

recommendation for controlling floating mats of a l l igatorweed, and the

feasi b i 1 i ty o f maintenance control of a1 1 i gatorweed; n o t for d a t a

collection.

7

Rooted A l l i g a t o r w e e d

Var ious herb ic ides , r a t e s , and h e r b i c i d e combinat ions were eva lua ted

f o r e f f e c t i v e n e s s o f c o n t r o l l i n g rooted-emersed a l l i g a t o r w e e d i n sha l low

drainage canal s l o c a t e d i n t h e Coastal P l a i n p r o v i n c e o f Nor th Carol ina.

A l l appl c a t i o n s were made t o wet f o l i a g e ( o r u n i f o r m l y cover t h e d i t c h

bank and bottom) by handgun u s i n g a D-8 nozzle. P l o t s izes were 400 m2

o r l a r g e so t h a t o p e r a t i o n a l l e v e l h e r b i c i d e a p p l i c a t i o n c o u l d be

simulated.

l o c a t e d i n d i f f e r e n t c o u n t i e s where poss ib le .

ways p o s s i b l e t o r e p l i c a t e t reatments, due t o v a r i o u s c o n s t r a i n t s , l a r g e

p l o t s i z e shoul d average t h e e v a l u a t i o n over most environmental

v a r i a b i l i t y . Obvious environmental d i f f e r e n c e s among rep1 i c a t i o n s a r e

noted i n t h e t e x t .

Treatments were r e p l i c a t e d w i t h i n a d i t c h , and among d i t c h e s

Al though i t was n o t a l -

H e r b i c i d e e f f i c a c y was eva lua ted s u b j e c t i v e l y on a sca le between 0

and 100 where 0 represents t h e c o n d i t i o n where a l l v i s i b l e v e g e t a t i o n

remains l i v i n g a f t e r h e r b i c i d e a p p l i c a t i o n , and 100 represents t h e con-

d i t i o n where a l l v i s i b l e v e g e t a t i o n i s apparent ly moribund.

S t a t i s t i c a l a n a l y s i s o f t h e da ta i s purposely o m i t t e d because some

t reatments a r e n o t r e p l i c a t e d , and/or N i s small f o r r e p l i c a t e d

t reatments; and because s t a t i s t i c a l a n a l y s i s i s probably n o t a p p r o p r i a t e

f o r s u b j e c t i v e r a t i n g s . Rather, a l l data a r e repor ted. Furthermore,

because any th ing l e s s than excel l e n t (90-100) 1 ong-term a l l igatorweed

c o n t r o l i s unacceptable, s i n c e r a p i d regrowth and renewal o f t h e problem

w i l l occur, d e t e c t i o n o f d e l i c a t e d i f f e r e n c e s between t reatments i s n o t

necessary.

3

RESULTS AND DISCUSSION

A1 1 igatorweed Survey

A l l igatorweed i s , e s s e n t i a l l y , con f i ned t o t h e Coastal P l a i n

p rov ince i n North Caro l i na b u t i s widespread and l o c a l l y abundant i n

t h i s area. Twenty-nine o f f o r t y - f i v e Coastal P1 a i n coun t ies r e p o r t e d

a l l i g a t o r w e e d occurrences ( F i g u r e 1). The o n l y non-Coastal P l a i n occur-

rences r e p o r t e d were a small pa tch i n one pond and one t e r r e s t r i a l oc-

currence ( t h a t has r e p o r t e d l y been e l i m i n a t e d ) i n S tan ly County i n t h e

Piedmont P la teau province, and one occurrence i n Woodlake i n Noore

County, an occurrence i n a l a k e i n Lee County, and i n one pond i n Yance

County. The l a t t e r two occur i n the S a n d h i l l s province. Actual area o f

i n f e s t a t i o n o f a l l i g a t o r w e e d ( o r o t h e r vege ta t i on ) i s o f t e n d i f f i c u l t t o

determine when i t occurs.

o f t e n i n a c c e s s i b l e o r , i n t h e case o f t e r r e s t r i a l a l l i g a t o r w e e d i n New

Hanover County, i t i s widespread throughout the county and i n d i v i d u a l

i n s p e c t i o n s would n o t have been f e a s i b l e .

dens i t y i n t h e county as widespread ( W ) o r sparse ( S ) and un-estimable

(UE). Tota l areas o f i n f e s t a t i o n should, t he re fo re , be construed re1 a-

t i v e l y r a t h e r than abso lu te l y . Our es t imated t o t a l s are probably under-

es t imates because where a l l i g a t o r w e e d was considered un-estimable i t was

n o t i n c l uded i n the t o t a l s.

For ins tance, p o r t i o n s o f an i n f e s t a t i o n are

I n such cases we have l i s t e d

T e r r e s t r i a l a l l i g a t o r w e e d i s very s c a t t e r e d i n the Coastal P l a i n o f

North Caro l ina . It occurs i n o n l y seven coun t ies (Table 1). However,

i t i s l o c a l l y abundant i n those coun t ies where i t occurs and we have ob-

served severe problems caused t o soybeans and ornamental p l a n t produc-

t i o n caused by heavy i n f e s t a t i o n .

9

0 20 40 60 80 100

1 I 1 1 , J SCALE IN MILES

Figure 1. North Carolina counties (shaded) that reported alligatorweed (Alternanthera philoxeroides)

during 1984.

-

Tab1 e 1.

occurrence i n North Carol i n a counties reported by county agricultural

Summary of a1 1 igatorweed ( A 1 ternanthera philoxeroides)

extension service offices, soil conservationists, and d i s t r i c t f isher ies

biologists d u r i n g 1984 survey.

County

Type o f Occurrence -- Streams

Drainage Ponds o r and

Terrestrial Canals Lakes Rivers

hectares

Beaufort

B1 aden

Brunswick

Camden

Chowan

Col umbus

Cumber1 and

Curri tuck

Dare

Dupl in

Edgecombe

Hertford

Hyde

Johns ton

0

0

0

0

0

810

0

0

0

0

0

0

4

0

0

34

4

0

0

40

W - U E

0

0

(1

16

0

9

0

0

4

6

0

8 1

128

10

2

0

14

0

3

2

<1

S-UE

0

127

S-UE

S-UE

119

0

0

S-UE

0

0

S-UE

0

0

11

Table 1. Continued

M a r t i n

New Hanover

Northampton

Onsl ow

Pasquotank

Pender

Perquimans

P i tt

Robeson

Sampson

Stan ly

Scot1 and

T y r r e l l

Vance

Washington

Wayne

0

W-UE

4

0

0

S-UE

5

W-UE

0

0

<1

0

162

0

62

0

0

W-UE

0

0

W-UE

0

6

W-UE

23

0

0

0

65

0

19

0

0

w-u

2

4

0

1

0

0

47

1

>1

1

0

1

0

56

W-UE

U-E

0

0

W-UE

0

W-UE

0

142

0

0

0

45

0

12

S-UE

Tota l 1,042 216 362 445

1 2

A total of 362 ha o f alligatorweed occurring in ponds and lakes was

Most o f these reported in 65% o f the counties t h a t contained the weed.

occurrences were in private impoundments. The only reported occurrences

of alligatorweed in public lakes were i n Lake Waccamaw and Lake Tabor i n

Columbus County and Greenfield Lake in Wilmington. Small ponds, or

coves of large lakes can become to ta l ly covered by floating a l -

ligatorweed mats.

Alligatorweed occurs i n ten North Carolina coastal r ivers , the

Alligator, Cape Fear, L i t t l e (Pasquotank co., Perquimans Co.) , Lumber,

Pam1 ico, Pasquotank, Scuppernong, Tar, and Waccamaw; and along the shore

of the Albemarle Sound. I t i s n o t reported t o cause problems i n open

water or wide river reaches, except for occasionally obstructing boat

s l ips or boat docks. I ts major impact i s exerted i n the upper narrow

river reaches, small creeks and bays, and drainage canals where i t can

completely stop navigation by forming extensive mats that extend from

one side of the water body t o the other.

severe flooding when mats break loose and p i le up a t water-course

rest r ic t ions d u r i n g heavy precipi t a t i o n .

Restricted waterflow can cause

A1 t h o u g h a1 1 igatorweed i s widespread throughout the coastal pl a i n

province, two major locations of heavy infestations occur (Figure 2 ) .

One of these i s i n the Northeast t h a t includes the Pasquotank, Chowan,

Roanoke, and Tar-Pamlico drainages, from the Pasquotank River t o

Tranter's Creek. The other i s i n the southeast corner of the s t a t e and

includes the Cape Fear and Lumber drainage basins from the S o u t h River

southwest into South Carolina.

Severe problems have been reported i n the northeast location i n the

Scuppernong River and t r ibutar ies where b o a t passage has become

13

iJ; c c

impossible i n reaches above Cross Landing.

sary t o remove blockages from bridges crossing the river and

t r ibutar ies .

d r a i n into the Scuppernong River and i n drainage canals located in other

areas of Washington and Tyrrell Counties t o t a l s 84 ha. T h i s i s a sub-

s tant ia l area considering that t h i s represents 339 km of canals

(assuming an average canal w i d t h o f 2.5m) t h a t can indirectly a f fec t

large cropland and residential areas by causing flooding. Other major

alligatorweed infestations associated w i t h the northeast location occur

i n the Pasquotank River and t r ibutar ies , L i t t l e River, Symond Creek,

Hal 1 ' s Creek, Mackey' s Creek, Canaby Creek, Ahoskie Creek, Tranter' s

Creek, and drainage canal s in Hyde County.

Draglines are often neces-

Alligatorweed in drainage canals below Phelps Lake that

Alligatorweed infestations i n the southeast location are associated

One hundred and sixty five mainly w i t h the Lumber and Waccamaw Rivers.

ha of alligatorweed were reported i n the Lumber River and t r ibutar ies .

These include Back Swamp, Li t t le Jacobs Swamp, Jacobs Swamp, Big Swamp,

and Old Field Swamp. One hundred and seventy five ha of alligatorweed

were reported in the Waccamaw River and t r ibutar ies t h a t include Gris-

s e t t Swamp, Seven Creeks, CawCaw Swamp, White Marsh, Fryer Swamp, Scip-

p i 0 Creek, Wet Ash Swamp, and Bear Branch.

l oc i , 49 ha of alligatorweed were reported i n Harrison Creek, Turnbull

Creek, Livingston Creek, Town Creek, Hoods Creek, and Sturgeon Creek

that d r a i n i n t o the Cape Fear River, and Lyons Swamp Canal that drains

i n t o the South River.

On the periphery of this

The 1043 ha of aquatic alligatorweed i n North Caroline estimated in

th i s survey i s in contrast t o 153 ha reported i n 1963 {USACE, 1965).

T h i s apparent six-fold increase in a twelve-year time span i s a good ex-

a

15

ample of the rate a t which a noxious aquatic weed can become a major

water resource problem i f not managed a t a maintenance control level.

Biological Suppressants

A1 1 i gatorweed F1 ea Beet1 e

A1 ligatorweed f lea beetles d i d n o t resul t i n measurable control of al-

ligatorweed a t the s i t e s i n Sampson and Pender counties where poten-

t i a l l y cold-tolerant insects were released.

ber and October 1983 revealed only minor feeding by the insects; and

several inspections d u r i n g 1984 revealed no evidence t h a t the insects

had overwintered.

Inspections d u r i n g Septem-

Early June i s the ea r l i e s t t h a t alligatorweed f lea beetles can be

expected t o be available i n suff ic ient quantity for mass release from

collection areas i n Florida. A t the time of our release on June 7 , 1984

the Thirty-foot Canal was 30% covered w i t h alligatorweed. Ideally we

would l ike t o be able t o introduce the insects when the mats are just

in i t ia t ing from the canal banks so a s t o prevent growth t o t h i s level.

A t the alligatorweed coverage that was present, our release rate was ap-

proximately 10 insects/m-2 of vegetation.

t ively restr ic ted by canal banks and a culvert a t the end of the release

s i t e we hoped t o see some reduction of the alligatorweed mats as the

population increased; and we planned t o apply herbicides t o p a r t of the

release s i t e t o determine i f the insects could be used along with her-

bicides t o prevent regrowth. However, nature intervened.

Since the ha ts i ta t was re1 a-

Five weeks a f te r release of alligatorweed f lea beetles, heavy

precipitation occurred t h a t caused alligatorweed mats i n the Th i r ty - foo t

16

canal t o break loose. Vegetation piled up against the culvert a t the

end of the release s i t e , and a f t e r severe flooding of adjacent f ie lds

occurred, the vegetation was removed by dragline. Several days a f t e r

th i s occurrence alligatorweed f lea beetles were observed feeding on the

piled up alligatorweed and a residual population was observed feeding on

the small amount of alligatorweed attached along the canal bank . This

was an excellent opportunity t o determine i f an existing popu la t ion of

alligatorweed flea beetles could prevent regrowth o f alligatorweed.

Three weeks a f te r the precipitation occurrence beetle-feeding was s t i l l

evident b u t the alligatorweed was reforming a mat outwardly from the

canal bank. Disappointingly, a1 1 igatorweed had regrown t o 30-50%

coverage o f the canal water surface by mid-October ( f i f teen weeks).

Based on observations made d u r i n g this project and on previous a t -

tempts t o establish alligatorweed f lea beetles i n North Carolina

(Langel and e t a1 , 1983)

potential a1 1 igatorweed

strain i s selected that

cause suppression of a1

we do not consider use of these insects a s a

suppressant in th i s area unless a cold-tolerant

will overwinter i n suff ic ient populations t o

igatorweed as i t emerges i n spr ing . And, based

on the apparent inabi l i ty of alligatorweed f lea beetles t o suppress mat

expansion i n th i s study, i t i s s t i l l questionable whether a cold

tolerant selection will be effective.

Alligatorweed Stemborer

Alligatorweed stemborer releases were n o t made d u r i n g this project,

however, d u r i n g the extensive traveling th rough Coastal P a i n areas t o

evaluate herbicide applications, damage from naturally occurring popula-

tions of these insects was noted. Damage from alligatorweed stemborer,

17

observed a s w i l t i n g ap ica l stem p o r t i o n s , t o t a l l y n e c r o t i c i c stems, o r

completely n e c r o t i c mats was widespread from mid-August through October.

Many mats t h a t became t o t a l l y n e c r o t i c began t o regrow from sp rou t ing o r

a x i l l a r y buds a f t e r the insect popula t ion had appa ren t ly diminished o r

moved.

ahead of the damaged a rea .

y e a r and i s no t complete enough t o o f f e r a l l i ga to rweed c o n t r o l .

the most damaged mats present as g r e a t a p o t e n t i a l f looding problem a n d

naviga t ion impedance a s the hea l thy mat.

Mats were sometimes observed t o cont inue growth and expansion

Unfor tuna te ly , damage occurs too l a t e i n the

Even

I t has been suggested (USAE, WES 1373) t h a t mat d e s t r u c t i o n by i n -

sects l a t e i n t h e growing season could cause reduced vege ta t ion density

o r e l imina t ion the fo l lowing growing season. T h i s phenomenon was n o t

observed. Alligatorweed mats grew back r a p i d l y the fo l lowing y e a r where

complete n e c r o s i s of the upper mat had been observed the previous y e a r .

I t i s unc lear whether a l l i ga to rweed stemborers survive winter i n

North Caro l ina o r whether observed popula t ions migra te from more

s o u t h e r l y l o c a t i o n s .

stemborers have upon a l l i ga to rweed growth, e a r l y s p r i n g feeding may

cause growth suppression. However, a better understanding of the

insect's population ecology w i l l be necessary t o determine the

f e a s i b i l i t y o f i t s use a s a b io log ica l suppres san t f o r a l l i ga to rweed i n

North Caro l ina .

Considering the d e v a s t a t i n g temporary impact t h a t

Herbicide Eva1 ua t ion

F1 o a t i n g A1 1 igatorweed

Few h e r b i c i d e s a r e registered by the EPA f o r a p p l i c a t i o n t o a l -

18

ligatorweed growing i n aquatic s i tes .

with 0.5% non-ionic surfactant i s recommended fo r alligatorweed

management, a1 though repeat treatment will probably be necessary2.

demonstrate the effectiveness of this application for controlling al-

ligatorweed and, t h u s , the feas ib i l i ty of implementing a maintenance a l -

ligatorweed management program, we cooperated w i t h the North Carolina

Department of Natural Resources and Community Development, Division of

Water Resources, i n reducing the alligatorweed infestation i n the Scup-

pernong River, between the bridge on county road 1155 and the Nashington

County l i ne , t o a maintenance level. The i n i t i a l application of

glyphosate t o the 2.5 ha o f alligatorweed t h a t had been rendering the

river completely non-navigable was reduced by abou t 90%. By the time of

the second application ( 9 weeks) regrowth was occurring from some of the

treated vegetation, whereas some mats had to ta l ly disappeared.

mats apparently break up sufficiently a f te r glyphosate appl ication t o

allow them t o be carried away by the river current.

reapplied t o sprouting alligatorweed i n previously treated areas, and

some areas t h a t were inaccessible i n October were treated.

A 1.25% solution of glyphosate

To

Some

Glyphosate was

By the s p r i n g o f 1985, alligatorweed was well under control i n the

I984 demonstration area. Only maintenance spot applications were needed

for alligatorweed mats t h a t had broken loose from oxbows t h a t were inac-

cessible i n 1984, and for alligatorweed rooted on the bank t h a t was

beginning to form floating mats.

*Rodeo herbicide f o r Aquatic Vegetation Management, Technical

f4anua1, Monsanto Ag. Prod. Co., St. Louis, Missouri 63167.

19

The f e a s i b i l i t y of implementing a maintenance a l l i ga to rweed manage-

ment program was c l e a r l y demonstrated.

United S t a t e s Army Corps of Engineers "Aquatic P1 a n t Control Program

(Rivers and Harbors Act 1965)" the c o s t o f th i s p r o j e c t t o the s t a t e and

Washington County was only $1190.

river channel were reopened t o pub l i c boa t ing access , a s e r i o u s f lood

p o t e n t i a l was removed, and the need f o r r o u t i n e d r a g l i n i n g a t river

Using matching funds from the

For this e f f o r t s eve ra l miles o f

br idges was e l imina ted . Benefit a n a l y s i s f o r th i s p r o j e c t i s r epor t ed

i n foo tno te 1.

Synergism Between Glyphosate and F1 uridone f o r Control 1 i n g

A l l igatorweed.

l iga torweed a lone and tank-mixed t o test f o r synergism between the two

Glyphosate and f l uridone were appl ied t o rooted a1 -

herb ic ides .

Exce l l en t con t ro l (90-100%) was observed two and fou r weeks a f t e r

a p p l i c a t i o n (WAA) o f g lyphosa te a t r a t e s of 0.18 and 0.36 Kg ae/100 L

( fol i a g e sprayed t o wet) when appl i e d i n 1 a t e summer (Tab1 e 2 ) . Her-

b i c i d e damage was observed a s t o t a l n e c r o s i s and dea th of the upper por-

t i o n s o f the a l l i ga to rweed mat. However, sp rou t ing of a x i l l a r y buds

from lower i n the mat o r from rhizomes was observed six WAA; and by nine

WAA con t ro l was poor (70%) i n those p l o t s eva lua ted (Table 2 ) . For ty

e i g h t WAA ( s p r i n g of the fo l lowing y e a r ) con t ro l was n i l t o f a i r i n a l l

p l o t s . No con t ro l was observed s i x t y WAA when g lyphosa te was no t reap-

p l i e d the fo l lowing yea r .

g lyphosa te a t 0.36 Kg ae/100 L i n midsummer, con t ro l was poor sixteen

WAA and con t ro l was n i l t o poor 48 WAA.

When p l o t s d i d receive r e a p p l i c a t i o n of

The l a r g e number of a x i l l a r y buds t h a t produce g lyphosa te symptom-

f r e e growth and subsequent regrowth of the mat i s s u r p r i s i n g cons ide r ing

20

Table 2. Efficacy of glyphosate and fluridone, when applied alone or

together, for controlling alligatorweed (Alternanthera philoxeroides) i n

shallow drainage canals i n Washington and Perquimans Counties, NC.

Herbicide & Ratel Level of Control2 a t Weeks After Date of

( k g ail100 L ) First Applic. Second Applic. Applic.

2 4 6 9 48 60 16 48 1st 2nd

Glyphosate (4L) 0.18 90 - - 40 0 0 - - 9/83 -- Glyphosate (4L) 0.36 - 99 80 - 0 - 50 50 8/83 7/84

- 99 95 - 70 - 20 0 8/83 7/84

- 98 90 - 60 - 20 0 8/83 7/84

98 - - 40 50 0 - - 9/83 - Fluridone ( 4 A S ) 0.24 - 0 50 - 0 - - - 8/83 -

- 50 50 - 0 - 50 50 8/83 7/84

- 0 5 0 - 0 - - - 8/83 - 50 - - 90 0 0 - - 9/83 -

Glyphosate (4L) 0.18+ 40 - - 100 80 0 - - 9/83 - F1 uridone (4AS) 0.12

Glyphosate (4L) 0.36+ - 99 98 - 0 - 80 50 8/83 7/84 Fluridone (4AS) 0.24 - 100 99 - o - 98 50 8/83 7/84

- 100 99 - 60 - 98 50 8/83 7/84

'All t a n k mixes contained 0.50% non-ionic surfactant, 0.075%

polyacryl amide copolymer and were applied t o wet f o l i age by handgun w i t h

a D-8 nozzle.

'0 = a17 vegetation l iving, 100 = a l l vegetation moribund.

21

the t r a n s l o c a t i o n o f glyphosate i n many o t h e r p l a n t s (Sprangle e t a l ,

1975; Claus and Behrens, 1976) . Glyphosate i s appa ren t ly n o t t r a n s l o -

c a t e d t o the q u i e s c e n t buds, and/or metabolized a t / o r be fo re i t reaches

the a x i l l a r y buds i n a l l igatorweed. We observed t h a t i n i t i a l response

o f a l l i ga to rweed t o glyphosate and o t h e r herbicides i s l e a f a b s c i s s i o n

and nodal absc i s s ion . Therefore , we s p e c u l a t e t h a t much o f the

glyphosate i s l o s t i n t h i s manner be fo re i t can be t r a n s l o c a t e d t o p l a n t

p a r t s t h a t a r e underwater, underground, o r otherwise p ro tec t ed from the

herbicide spray.

A1 1 igatorweed responded i n c o n s i s t e n t l y t o f l u r idone appl ied i n 1 a t e

summer a t a r a t e of 0.24 kg a i /100 L ( f o l i a g e sprayed t o wet).

con t ro l was observed f o u r WAA i n p l o t s where a l l i ga to rweed was growing

i n damp s o i l (Table 2 , p l o t s treated 8/83) (d ra inage had been diverted

t o ano the r canal due t o blockages caused by a l l igatorweed) . most l e a v e s had absc i sed , stems were inconsistently c h l o r o t i c , and many

i n i t i a t i n g buds were c h l o r o t i c and a b o r t i n g , However, vigorously grow-

ing buds without symptoms were a l s o beginning t o appear, and con t ro l was

poor. F lu r idone d i d no t con t ro l a l l i ga to rweed i n these p l o t s f o r t y -

e i g h t WAA.

aga in i n on ly poor con t ro l the y e a r o f a p p l i c a t i o n (Table 2 ) .

percen t suppression was observed throughout the fo l lowing y e a r i n th i s

p l o t w i t h some f l uridone symptoms s t i l l apparent .

f luridone (0.24 kg a i /100 L) t o a l l i ga to rweed growing i n a d i t c h con-

t a i n i n g some s t a t i c water and supe r - sa tu ra t ed s o i l resulted i n e x c e l l e n t

con t ro l throughout the growing season (Table 2 , p l o t t r e a t e d 9 /83) , b u t

no r e s idua l con t ro l was observed the fol lowing y e a r .

Poor

S ix WAA

Reappl icat ion o f f luridone t o one o f these p l o t s resulted

F i f t y

Appl i c a t i o n o f

The i n ? t i a l response of a1 1 igatorweed growing i n damp s o i l (Table 2 ,

2 2

t r e a t e d 8/83) t o a p p l i c a t i o n o f a tank mix o f 0.36 kg ae g lyphosate and

0.24 kg a i f lu r idone/100 L was s i m i l a r t o t h a t o f g lyphosate alone.

c e l l e n t c o n t r o l was observed f o u r WAA. A x i l l a r y buds t h a t sprouted

a f t e r t h i s appl i c a t i o n e x h i b i t e d f l ur idone symptoms and abor ted s h o r t l y

a f t e r i n i t i a t i o n .

e x c e l l e n t c o n t r o l i n a l l damp s o i l p l o t s s i x WAA. Th is was somewhat

b e t t e r than the good t o e x c e l l e n t c o n t r o l observed w i t h g lyphosate a lone

and cons iderab ly b e t t e r than t h e poor c o n t r o l observed w i t h f l u r i d o n e

alone. N i l t o poor c o n t r o l o f a l l i g a t o r w e e d was observed f o r t y - e i g h t

WAA i n these p l o t s , which i s s i m i l a r t o the response observed w i t h

g lyphosate o r f l u r i d o n e alone. Re-app l ica t ion o f t h e tank mix t o these

p l o t s t h e f o l l o w i n g y e a r r e s u l t e d i n good t o e x c e l l e n t c o n t r o l f o r most

of t h e growing season compared t o poor c o n t r o l a f t e r r e a p p l i c a t i o n o f

t h e compounds by themselves; 50% suppression was e v i d e n t c o n s i s t e n t l y

Ex-

T h i s e f f e c t on s p r o u t i n g a x i l l a r y buds r e s u l t e d i n

t h e f o l l o w i n g year .

A p p l i c a t i o n o f g lyphosate and f l u r i d o n e tank-mixed a t r a t e s o f 0.18

k g ae + 0.12 kg a i /100 L, o r 0.36 kg ae + 0.24 kg a i /100 L t o a l -

l i g a t o r w e e d growing i n d i t c h e s c o n t a i n i n g some s t a t i c water and super-

s a t u r a t e d s o i l r e s u l t e d i n e x c e l l e n t c o n t r o l (Table 2, p l o t s t r e a t e d

9/83) for the n i n e weeks remain ing i n t h e growing season t h e y e a r o f

a p p l i c a t i o n .

served w i t h g lyphosate a lone b u t s i m i l a r t o t h e response o f f l u r i d o n e

a lone i n a s t a t i c water /supersaturated s i t u a t i o n ,

creased a c t i v i t y o f f l u r i d o n e a lone o r tank-mixed w i t h g lyphosate i n t h e

w e t t e r s o i l suggests t h a t f l u r i d o n e uptake i s f a c i l i t a t e d by t h i s

c o n d i t i o n , and the e f f i c a c y o f f l u r i d o n e f o r c o n t r o l l i n g r o o t e d a l -

l i g a t o r w e e d i s s e n s i t i v e t o s o i l mois ture. Good c o n t r o l was e v i d e n t

Th is response i s again cons iderab ly b e t t e r than t h a t ob-

The apparent i n -

23

forty-eight WAA of b o t h rates of tank-mixed glyphosate and fluridone i n

the super-saturated plots (Table 2, plots treated 9/83). However, con-

trol did n o t pers is t through the following growing season.

Effect of Glyphosate Concentration on Level of Alligatorweed Control.

Although a great deal of var iabi l i ty was observed w i t h i n the two rates

of glyphosate t h a t were replicated, a trend toward increased a l -

ligatorweed control was observed a s the concentration of glyphosate was

increased between 0.24 and 0.96 kg ae/100 L (Table 3) where applied in

June.

lowest rate was applied.

served w i t h 0.36 kg ae/100 L , b u t control was poor eight WAA and l o s t by

eighteen WAA in a l l plots. Likewise, control was i n i t i a l l y excellent i n

an unreplicated plot where 0.48 kg ae/100L was applied, b u t control was

poor by eight WAA and nil 18 WAA. A t 0.60 kg ae/100 L , the recommended

rate f o r a7 1 igatorweed control , i n i t i a l control was a1 so poor t o

excellent, was s t i l l poor t o excellent eight WAA and was n i l t o poor by

eighteen WAA. A t 0.96 kg ae/100 L , somewhat higher t h a n the label ra te ,

excellent control was observed through eight WAA in a n unreplicated

plot.

Poor control was observed i n the unreplicated plot where the

Poor t o excellent control was i n i t i a l l y ob-

However, even a t this rate , control was poor eighteen WAA.

The somewhat reduced control observed w i t h 0.36 kg ae/100 L , and

w i t h 0.60 k g ae/100 L applied i n June, as compared t o 0.36 kg ae/100 L

applied in August and September ( c f . Table 2 and Table 31, may be re-

lated t o the physiological age o f the alligatorweed, which allowed for

even less translocation of the compound.

plants may have caused th i s reduced control because large numbers o f

dormant buds had not in i t ia ted and were protected from the herbicide

The developmental stage of the

spray.

24

Table 3.

a1 1 igatorweed ( A 1 t e rnan the ra ph i loxe ro ides ) i n shallow dra inage c a n a l s

l o c a t e d i n Washington and Tyr re l l Counties, NC, when app l i ed i n June,

1984 or reapp l i ed i n October, 1984.

Ef f icacy of va r ious r a t e s of g lyphosa te f o r c o n t r o l l i n g

Level of Control2 Level of Control2

a t a t

Ratel Weeks After Weeks A f t e r

(Kg - ae/100 L) First Appl ica t ion Second Appl ica t ion

2 8 18 4 32 40

- - - 0.24 50 40 0

0.36

0.48

0.50

- - 50 70 0

95 50 0 - - 70 10 10 - - 50 10 0 100 50 0

- - - 70 50 30

80 10 0 - 0.96 100 100 20 - - - lA17 tank mixes conta ined 0.50% non-ionic s u r f a c t a n t , 0.075%

- -

polyacrylamide copolymer and were app l i ed t o wet f o l i a g e by handgun w i t h

a 0-8 nozzle.

'0 = a l l vege ta t ion a l i v e , 100 = a l l vege ta t ion moribund.

25

E f f i c a c y o f 2,4-D and Dicamba f o r C o n t r o l l i n g A l l igatorweed.

t i o n o f 2,4-D, dicamba, and a formulated combinat ion o f these h e r b i c i d e s

a t recommended r a t e s f o r perenn ia l b road lea f weed c o n t r o l r e s u l t e d i n

good t o e x c e l l e n t i n i t i a l c o n t r o l w i t h 2,4-D and e x c e l l e n t i n i t i a l con-

t r o l w i t h dicamba o r t h e fo rmula ted combinat ion (Tab le 4 ) , when a p p l i e d

i n spr ing, t h e t ime when these compounds should be most e f f e c t i v e .

A f t e r t h e i n i t i a l damage from t h e h e r b i c i d e s (observed as t o t a l dest ruc-

t i o n o f t h e upper p o r t i o n s o f t h e mat), s p r o u t i n g o f a x i l l a r y buds f rom

lower p o r t i o n s o f the mat and fragmented vegeta t ion began and regrowth

was r a p i d , r e s u l t i n g i n poor c o n t r o l e i g h t WAA and no c o n t r o l e igh teen

WAA.

absc iss ion a r e probab y respons ib le f o r t h e apparent l a c k o f t r a n s l o c a -

t i o n and poor c o n t r o l a t t h e r a t e s o f these compounds t h a t were used

and, which a r e e f f e c t ve f o r c o n t r o l l i n g many o t h e r b road lea f p l a n t s .

Appl i c a -

As suggested f o r glyphosate, r a p i d w i l t i n g and l e a f and nodal

E f f i c a c y o f Imazapyr f o r C o n t r o l l i n g A l l iga torweed.

l i g a t o r w e e d appeared s l o w l y a f t e r a p p l i c a t i o n o f 0.03, 0.06, o r 0.12 k g

ae imazapyr/100 L.

a p i c a l bud and a p i c a l growth f o l l o w e d by a b o r t i o n o f a p i c a l buds. These

symptoms were subsequently ( f o u r weeks) observed on a x i l 1 a r y growth,

Symptoms appeared somewhat more r a p i d l y w i t h i n c r e a s i n g concent ra t ion ,

b u t c o n t r o l was slow t o occur i n a l l cases. Two SJAA, no c o n t r o l was ob-

Damage t o a l -

Symptoms were f i r s t observed as e t i o l a t i o n o f t h e

served a t t h e lowest r a t e , n i l t o poor c o n t r o l a t t h e midd le r a t e , and

26

Table 4. Eff icacy of 2,4-D and dicamba f o r c o n t r o l l i n g a l l i ga to rweed

( A I t e rnan the ra phi loxero ides) i n a shallow dra inage canal l oca t ed i n

Tyr re l l County, NC, when app l i ed i n June, 1984.

Level of Control2

Ratel a t

(Kg ae/100 L) Weeks Af te r Appl ica t ion -- - - Herbicide

2 8 18

2,4-D (dimethylamine) 0.46 80 50 0

2,4-D (dodecylamine (47.3%) 0.32 85 50 0

80 50 0

90 30 0

98 20 0 Dicamba (dimethyl amine) 0.48

100 60 0

95 50 0

D i camba ( dimethyl ami ne + 0. ?2+0.23 98 50 0

2,4-0 (dimethylamine) 100 60 0

99 50 0

"17 tank mixes contained 0.50% non-ionic s u r f a c t r a n t , 0.075%

polyacrylamide copolymer and were appl ied t o wet f o l i a g e by handgun w i t h

a D-8 nozzle.

= a l l vege ta t ive a l i v e , 100 = a l l vege ta t ion moribund.

27

Table 5. E f f i cacy of imazapyr f o r con t ro l1 ing a l l igatorweed

( A 4 t e r n a n t h e r a p h i 9 oxeroi des ) i n s h a l l ow d r a i nage canal s 1 ocated i n

Washington, T y r r e l l , and Perquimans Counties, NC.

Level o f Control2 Level o f Control2

a t a t

Rate l Weeks After Weeks After

(Kg e ae/100 - - L ) F i r s t Applicat ion Second Applicat ion Applic.Date

2nd - 1st - 16 48 - - - - - .__ - 2 8 18 38 60

0.03 0 100

0.06 0 100

20 98

50 100

0 95

0.12 0 100

50 95

80 99

50 100

100 100

100 --

8/83 -- 8/83 8/84

6/84 7/85

6/84

6/84

8/83 8/84

6/84 7/85

6/84

6/84

50 100 99 -- -- -- - 6 184

IAll tank mixes con ta ined 0.50% non-ionic s u r f a c t a n t , 0.075%

polyacrylamide copolymer, and were app l i ed t o wet f o l i a g e by handgun

w i t h a 0-8 nozzle.

2O = a l l vege ta t ion l i v i n g , 100 = a l l vege ta t ion moribund.

only poor t o good control a t the highest rate (Table 5 ) . The slow rate

a t which damage occurred t o alligatorweed af te r application o f imazapyr

may have allowed for good translocation o f the herbicide, t o which al-

ligatorweed i s apparently highly sensitive.

cel lent t o total control of alligatorweed was observed i n a l l plots, and

eighteen WAA, excellent t o almost total control was s t i l l observed in

a1 1 plots eval uated.

encroaching from areas of the ditchbank t h a t had been missed by the her-

bicide spray, and n o t from regrowth of the affected alligatorweed. Im-

azapyr gave season-long control of alligatorweed a f t e r spring or summer

application of a l l rates tested. In spring of the following year (48

WAA) , excellent control was s t i l l observed i n those p l o t s evaluated

(some plots were n o t evaluated further due t o flushing and movement of

alligatorweed mats in the ditches a f te r h i g h water conditions) where the

two higher rates had been applied, b u t control was now poor a t the

lowest rate. As was observed the previous year, l iving alligatorweed i n

plots where the higher rates were applied was apparently a resul t of n o t

receiving herbicide spray. However, a t the lowest concentration,

regrowth was occurring throughout the plot. Total regrowth occurred

sixty WAA of th i s lowest rate.

higher rates t o the small amount o f vegetation remaining in the plots

resulted i n apparent complete el iminaiion o f a l l igatorweed from the

E i g h t WAA of imazapyr, ex-

Living a1 1 i gatorweed i n the pl o t s was apparently

Re-application of e i ther of the two

p l o t s .

A concern when us ing a highly phytoactive compound such as imazapyr

for aquatic weed control i s movement of the compound i n water t o non-

target areas.

observed outside the application area.

I t i s therefore important t h a t imazapyr symptoms were n o t

A dis t inc t demarcation of l iving

29

and moribund vegetation occurred a t the edge of a l l plots.

apparently intercepted i n suff ic ient quantity by the target vegetation

and n o t released i n active form, or rendered inactive a f te r contact w i t h

water or soil i n the ditch.

Imazapyr was

Preliminary Unrepl icated Evaluations of Other Herbicides for Control1 i n g

Alligatorweed. Complete control o f alligatorweed was observed w i t h

tryclopyr a t a ra te of 0.36 kg ae/100 L six and twelve GIAA (Table 5 ) .

Translocation of the herbicide apparently occurred th roughou t the mat,

because axi l lary bud sprouting was never observed and l i v i n g rhizomes

could n o t be found i n the plot. Tryclopyr i s n o t presently registered

for aquatic weed control, b u t this labeling may be forthcoming.

Tryclopyr may offer the most economical control f o r rooted alligatorweed

and should be investigated further. Sul fmeturon methyl and metsul furon

methyl are closely related compounds t h a t gave f a i r t o good, and good t o

excellent control , respectively, when applied a t various rates (Table

6). Therefore, these two compounds offer some potential f o r use i n an

alligatorweed control program, b u t further investigations should only be

pursued i f the manufacturer indicates the potential for obtaining an EPA

registration for aquatic weed control.

and bromacil are compounds that are, a t l eas t , predominantly soil

Hexazinone, d i u r o n , fenatrol ,

active. Therefore, even though good t o excellent control was observed

w i t h these compounds (Table 6) , they will have only 1 imited application

i n an a l l igatorweed control program.

s i t i v i t y t o amitrole.

A1 1 igatorweed d i d n o t exhibit sen-

30

Table 6. Ef f icacy of severa l he rb ic ides f o r cont ro l of a l l iga torweed

(A1 t e rnan the ra phi loxero ides) i n shalow dra inage cana l s l oca t ed i n

Washington County, NC.

Herbicide & Ratel Applicat ion Level of Control2 a t

Weeks A f t e r Appl i c a t i o n

6 1 2 48 60

-- (a i /100 L) Date

D i uron 3.84 kg 9/83 100 -- 20 0

Fenatrol 3.90 10 /84 -- -- 100 -- 0 -- A m i t r o l e 1.44 io / a4 -- --

Bromaci 1 0.96 6/85 70 90 -- -- Hexazi none 0.96 6/85 80 ao -- -- P r i c l opyr 0.36 6/85 100 100 -- -_ Sulfmeturon methyl 33.75 g 8/85 75 -- -- --

-- -- 67 a 50 85 -- -- -- Metsul furon methyl 1.13 8/85 80 --

2.26

4.52

All tank mixes conta ined 0.50% non-ionic s u r f a c t a n t 0.075%

polyacryl ami de copolymer, and were appl ied by handgun t o uniformly cover

the canal bottom and bank.

*O = a l l vege ta t ion l i v i n g , 100 = a l l vege ta t ion moribund.

31

Literature Cited

Blackburn, R.D. 1963. Evaluating herbicides against aquatic weeds.

Weeds 11:21-25.

Blackburn, R.D. and W. Burden. 1974. Control of te r res t r ia l and rooted

alligatorweed. - I n Proc. S. Weed Sci. SOC. 1974.

only).

:283 (abstract

Buckingham, G.R. and D. Boucias. 1982. Release of potentially cold

to1 erant a1 1 igatorweed fl ea beet1 es (agasacl es hygrophyl a Sel man and

Vogt) into the United States from Argentina, Misc. Paper A-82-A,

U.S. Army Engineers Waterways Experiment S t a t i o n , Vicksburg, !IS.

C1 aus, J .J. and R. Behrens. 1976. Glyphosate trans1 ocation and quack-

grass budkill. Weed Sci. 24:149:176.

Gangstad, E.O. 1977. Biological control of alligatorweed, 1959-1972.

ARS, USDA and USACE. Washington, DC.

Gangstad, E.O. 1984. Aquatic use pattern of silvex cancellation. J.

Aquat. Plant. Manage. 22:78-80.

Langeland, K.A., C.A. Nalepa, and K.G. Wilson. 1984. S t a t u s of a1

ligatorweed contro i n North Carolina. - In Proceedings, 18th Annua

Meeting, Aquatic P a n t Control Research Program, 14-17 November,

1983, Raleigh,NC.

1967. Spencer, J.L. The effects of herbicides on seven species of

aquatic plants in the Mobile Delta. In S. Weed Conf. Proc. 20:319-

326. -

Sprankle, P., W.F. Meggit and D. Penner. 1975. Absorption, action, a n d

translocation of glyphosate. Weed Sci. 23:235-240.

Steenis, J.H. and F.B. McGilvery. 1961. Environmental factors effect-

32

i n g the c o n t r o l of a l l i g a t o r w e e d . - I n Proceedings of the S. Weed

Sei. Conf. f961:289-292.

U.S. Army Corps of Engineers . 1965. Expanded p r o j e c t f o r a q u a t i c p l a n t

c o n t r o l . 8 9 t h Cong., 1st Sess . , House Doc. No. 81. 148 pp.

U.S. Army Engineer Waterways Experiment S t a t i o n . 1981. The Use o f In-

sets t o Manage All igatorweed, I n t r o d u c t i o n Report A-81-1. O f f i c e ,

Chief of Engineers , U.S. Army, Washington, DC 20314.

Weldon, L.W. and R.D. Blackburn. 1967. The c o n t r o l of f l o a t i n g a q u a t i c

weeds w i t h ametryne. _. In Proc. S. Weed Conf. 1967:312-318.

Weldon, L.W., H.T. DeRigo, and R.D. Blackburn. 1968. Control o f a l -

l iga torweed w i t h d i c h l o b e n i l .

Conf. 1968:287-291.

- In Proceedings o f the S. Weed S c i .

Zurburg, F.W., I.S. Nelson, and J.A. F o r e t . 1961. An a s p e c t of the

h e r b i c i d a l a c t i o n of 2,4-D and r e l a t e d compounds i n a l l igatorweed

(A1 t e r n a n t h e r a p h i l o x e r o i d e s ) . - In Proc. S. Weed Conf. 1961:293-294.

33

Appendix

34

Crop Science Specialist - Keed Control Sox 7627’ Raleigh, NC 27695-7627

Xitgust 1 7 , 1584

TO: Ccunzy Ex:ension Ckiirsten, D i s t r i c t F i s h e r i e s 3 i o l o g i s t s , S o i l C s z s z r z a t i o n XSents

,‘ > [ ’4 FX-CX: ‘c. A. La-geland

We tire canduct lng a s u m e y t o d e t e m i n e t h e to:al acreage , a d e x t e n t o f ? r o b l e s caused by a i l i g a t c r J e e d ( A l i e ~ ~ ~ t h e r a s h i l c x e r s i d e s ) ( s o m e t k e s c a l l e d 9 i ; l e r i e e d in Z z s r e r n h’orrh Carolfca). Le ‘nope t h a t you can assist us tn t h i s e f f o r t .

A l l i g a t o r t e e d i s sn a q u a t i c p l a n t t h a t w a s in t roduced i n t o t h e United States f rm Scuth +*erica in t h e 1990’s. It h a s caused severe f l o o d i n g , l o s s o f r e c r e a c i o c t i l value of wazer r e s o u r c e s , and r e d u c t i o n In crop y i e l d s i n several c o a s t a l B o r t h C a r o l i n a c o u n t i e s . k’e belie\-? t h a t a s t a t e w i d e a l l i g a t o r d e e d z a n a g a e n t pi-ograiz, i nvo lv iag several a g c n c i e s c o u l d c o r r e c t c u r r e n t p r o b l e w :=used by a l l i g a t c r w e e d and Trevenr p o z e n t i a l p r o b l u n s . d o c u e n t z z i o o of t h e exrent of t h e p r o b l a .

P r e r e q u i s i t e to o r g a n i z i n g such a progrzm is

.Artached :TU w i l l f i n d a d e s c r 5 7 t i o n and ske tch of a l l i g a t a m e e d and a forin zhar w e z u s t c o q l e r e f o r each county. a s s i s t a n c e , p i e a s e c m p l e t e and r e t u r n to:

If you can c o q l e c e t h e r a b l e z i t h o u t o u r

K. A. Lazlgeland NCSU Weed Science Center 3123 L igon S t r e e t Raleigh, NC 27607 ?hone: 919/737-2866

?laps l o c a t i n g i n f e s t a t i o n s , d o c m e n t a t i o n of f l o o d i n g , h i s t o r i c 2 1 mtes , o r any o t h e r i n f o m t i o n r e l a t i n g t o a l l i g a t o r z e e d i n pour couzty o r area w i l l b e he l - s fc l . If you wauld l i k e a s s i s r a n c e i n i d e n t i f y i n g a l l i g a t o r d e e d o r i n conduczing tbe sune:?, please c o n t a c t =e s o that w e c t n assis: you. a - r e z s i o n ChaLmen, Dis t r ic t F i s h e r i e s S i o l o g i s t s , and Soil CcnsenatTon S c v i c 2 Agents, so p l e a s e c o o r d f z a t e v i t h rhese pecple t o ? revent d u p l i c a r i o n .

P l e a s e k f o z =le as t o hou you i z r e n d t o p a r t i c i F a r e , o r i f you c m n o t assist , 3y SeTtclz5er 1, 19884.

This r e q u e s t is be ing sznt t o Com:y -

Your c o o p e r a t i c n w i l l be g r e a r l y a p p r e c i a t e d .

m - 3 m ~ m t ~ w &tensLon Work in Agriculture and Home Economics A&T and .V. C. State LinLversrties. 100 Counties and 5. S. De.uartment of A-multure

AGRICULTURAL EXTENSION SERVICE

North Carolina State University School of Agriculture and Life Sciences

K. A, tangeland Crop Science Specialist - Weed Control Box 7627 Raleigh, NC 27695-7621 Phone - 919/737-2866

Alligatorweed (Alternanthera philoxeroides)

from E. 0. Beal, 1977

ALLIGATORWEED is an herbaceous plant that foras

dense floating mats on the water surface, can root into the substrate in shallow ditches and lake margins, and can invade moist s o i l s .

Leaves are elliptic to oblanceolate (broadest above the middle), entire (smooth

edges without teeth) and opposite. Stems are usually laying on the water surface o r ground and only weakly erect toward the ends. Roots often develop at the nodes (where leaf and stem join). Stems can be up to one inch thick in floating mats, but tend to be narrower when rooted. The stems are always hollow which distinguishes alligatorweed f rom similar plants such as smartweed (Polyganum spp.). Flowers are white and occur in round clusters at the end of spikes that arise from the upper leaf axils.

Major identifying characteristics

1. Opposite entire leaves 2 . Hollow stems 3. r3hite flowers

Coopemrive Ex:e.rsion Work in Agriculture and Home Economics A&T and N. C. State Lhioenitks, la0 Counties and I!,? S. Department ofA@U@r:W