Biological Control of Hydrilla

J.P. Cuda1, W.A. Overholt2, K.T. Gioeli3

and S.A. Hetrick4

1Entomology & Nematology Dept., Gainesville, FL 326112BioControl Research & Containment Lab., Ft. Pierce, FL 34945

3Osceola County Extension, Kissimmee, FL 347444St. Lucie County Extension, Ft. Pierce, FL 34945

Acknowledgements• Karen Brown• Mike Grodowitz• Mike Netherland• Tobias Schmid• Judy Shearer• Karen Stratman

• USDA NIFA Grant

Outline• Background Information• Current Activities• Future Directions• Questions? Comments?

Outline• Background Information

Prevention Chemical

Physical

Biological

IPM

Invasive Plant Management- The Other IPM

Adkins (1997)

Messersmith and Adkins. 1995. Weed Technol. 9:199-208.

What is Biological Control ?• Intentional Use of Natural Enemies

to Weaken and Suppress Invading Plants– Increase Leaf Mortality, Inhibit Growth,

Reduce Flower & Seed Production

• Three Categories:– Augmentation (Arthropods, Pathogens, Fish)

– Importation or Classical (Arthropods, Pathogens)

– Fortuitous (Arthropods, Pathogens)

TACTICS OF AQUATIC PLANT MANAGEMENT

BIOLOGICAL CHEMICAL PHYSICALPREVENTION

IMPORTATION ADVENTIVE AUGMENTATION INORGANICORGANIC

NATURAL SYNTHESIZED NATURAL SYNTHESIZED

PERMANENT TEMPORARY

Relative Degree of Sustainability

CLASSICAL INUNDATIVEFORTUITOUS

Importation (Classical) BioControl

• Introduction and Release of Host Specific Natural Enemies from the Weed’s Native Range to Reduce Its Growth, Reproduction or Density in the Adventive1

Range

1Arrived into a specified geographical region from elsewhere by ANY means.

Worldwide Distribution of Hydrilla

http://www.discoverlife.org/mp/20m?kind=Hydrilla+verticillata&guide=Aquatic_Invasives

cpDNA haplotypes

China F

China G

China H

Japan

Indonesia

Taiwan

12

19

1 China E6

5

3

4

2

7

1019

China A

China C

Korea,NE U.S.A

Australia,New Zealand

11

1

11

1

China B,India

China J China IPoland

China D

Florida, Texas, California, Louisiana,

Africa, India, Panama, Pakistan

22

11

Hydrilla Genetic Studies

Williams et al., unpubl.

Developing Classical BC Agents

Credit: M. Grodowitz USA, ERDC

Quarantine Facilities

USDA-ARS Laboratory, Ft. Lauderdale

UF/DACS Laboratory, Ft. Pierce

FL BioControl Lab, Gainesville

UF Entomology Dept, Gainesville

Goal of Classical BioControl

• Reunite the Natural Enemies with Their Host Plants to Suppress and Maintain the Density of the Weeds at “ACCEPTABLE” Levels

• Biological Control is NOT Eradication

How Does BioControl Work ?

TIME

NU

MB

ER

EIL

EDNatural Enemy

Weed

ED

• Weed establishes equilibrium density (ED)*above ecological or economic injury level (EIL)**

• Natural enemy lowers ED & maintains it below EIL

*ED - Long term mean density**EIL – Lowest density causing

economic or ecological damage

Advantages of Classical Weed BC

• Minimal Impact on Non-targets• Environmentally Friendly• Classical Biocontrol is Permanent• Suitable for Weeds of Natural

Areas and Aquatic Ecosystems• Relatively Inexpensive

Costs/Benefits of BioControl

(after Mentz 1987)

Release of Bioagent

Time

Benefits (+$)

Costs (-$)

Research & Development

Maintenance & Monitoring

Disadvantages of Classical BC

• Control is Not Immediate (5–10 years)

• Little Interest in Commercialization• Unpredictable

– Some Natural Enemies Fail to Establish– Some Natural Enemies are Ineffective

• Abiotic and Biotic Interference

Classical Hydrilla BioControl Agents

Hydrilla Tuber Weevil, Bagous affinis

Classical Hydrilla BioControl Agents

Hydrilla Stem Borer, Bagous hydrillae

Classical Hydrilla BioControl Agents

Hydrilla Leaf Miners, Hydrellia spp.

HYDRELLIA ADULT & LARVA

BioControl of Hydrilla

Factors Impacting Hydrellia

y = -53.114x + 2300.4R2 = 0.5772

0

400

800

1200

1600

2000

20 25 30 35 40 45

MAXIMUM TEMPERATURE (oC)

DE

NS

ITY

• Hydrilla Mat Surface Temperature

Factors Impacting Hydrellia• Predation by Damselfly & Dragonfly Naiads

0

200

400

600

800

1000

1200

1400

1600

1800

6-Ju

l-95

4-Aug-

95

13-S

ep-9

5

12-O

ct-95

9-Nov

-95

13-D

ec-95

29-Ja

n-96

28-F

eb-9

6

27-M

ar-9

6

29-A

pr-9

6

29-M

ay-9

6

25-Ju

n-96

24-Ju

l-96

27-A

ug-9

6

25-S

ep-9

6

22-O

ct-96

25-N

ov-96

28-Ja

n-97

0

50

100

150

200

250

300

HP LARVAE

DRAGONFLY NAIADS

UK

HY

DR

EL

LIA

DE

NS

ITY

(n

o. /

m2 )

DR

AG

ON

FLY

DE

NS

ITY

(no

. / m2)

Factors Impacting Hydrellia

• Parasitism– Significant– Upwards of 30%

• Late in growing season

– Pupal parasitoid behavior

• Selects wide range• Stage chosen =

most successful

TRICHOPRIA WASP

Augmentative BioControl

• Release of Large Numbers of a Biological Control Agent to Achieve a Rapid Effect

• There is No Expectation the Biological Control Agent will Establish a Permanent (= Reproducing) Population

Augmentative Hydrilla BioControl

GRASS CARP

• Sterile (Triploid) Grass Carp Used to Manage Hydrilla

• BUT- They Are Not Selective Feeders

• Can Only be Used in Closed Water Bodies

UF

Hydrilla Bioherbicide

Mycoleptodiscus terrestris(Native Fungal Pathogen)

Fortuitous (Adventive) BioControl

• Regulation of a Weed Population by a Natural Enemy that Has Arrived from Elsewhere WithoutDeliberate Introduction

• No Active Human Involvement

Fortuitous Hydrilla BioControlParapoynx Moth

• Adventive sp. from Asia• Collected in 1976,

Ft. Lauderdale Area• Hydrilla- Principle Host

Plant• Introduced via Aquarium

Trade• Damage to Hydrilla

Minimal & Sporadic ???– Poor BioControl Agent

© H. Clifford

• Midge Discovered in Crystal River 1992

• Identified Dec 1998– Collected in 1959,

Natchitoches, LA– Described 1964– Hydrilla in Louisiana ?– Natchitoches,1973

• Immigrant or Native Species ????

Male

Fortuitous Hydrilla BioControlCricotopus lebetis Sublette

Outline• Background Information• Current Activities

“Ideal” Hydrilla BioControl Agent• Narrow Host Range (=Safety)- Specialists• Damages Vital Plant Tissues (=Individual Effect)• Reproductively Prolific (=Population Effect)• Entire Life Cycle on Submersed Hydrilla• Amenable to Local Conditions (=Climate Match

& Habitat Conditions)• Thrives on Local Hydrilla (Biotype Match)• Protected from Predators (=Endophagous)

Source: T.D. Center, USDA-ARS

The Hydrilla Miner

• Tip- mining Midge- Larvae Feed on Living

Plant Tissue - Rare Occurrence

• Prevents “topping out”• Naturalized in Florida

- No Swarms- Low Dispersal Distance- Easily Mass Reared

Female

Larva

Life Cycle of Hydrilla Miner

Female

Larva

Pupa

Egg

Cuda et al. (1999, 2002)

Larva and Associated Tip Damage

Credit: D. Denson, RCID

Block 1: Control Block 1: Midge

Lake Rowell, Bradford Co.September 2010

Lake Rowell, Bradford Co.September 2010

Changing Hydrilla’s Architecture

Imazamox

Hydrilla Miner

Outline• Background Information• Current Activities• Future Directions

Research Goals• Develop Hydrilla Miner Rearing Methods

Research Goals• Conduct Host Range Tests

– Confirm Insect is Hydrilla Specialist

Research Goals• Establish Temperature Tolerances

– Growth Chamber Studies

Miner

Mt

Imazamox

Research Goals

Management Goals• Integrate Miner, Mt & Imazamox = IPM• Eliminate Adverse Effects of Surface Mats• Reduce Reliance on Herbicides• Create More Favorable Habitat

Future of Hydrilla?

With IPM

Without IPM

Questions?