Dissipation and Off-site Movement of Aerially Applied Forestry Herbicides

Pam WoffordDepartment of Pesticide Regulation

Tribal Environmental Work GroupKlamath, CA

February 14, 2001

Spring 2000: Two dissipation sampling sitesBeargrass

One off-site sampling siteBeargrass

Fall 2000: Two dissipation sampling sitesYarrowHuckleberryManzanita

Two off-site sampling sitesBeargrassHuckleberryYarrow

Plant Monitoring

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(/10 1

P

Q

S

1 0 1 2 Miles

Off-site Movement Sampling Sites

Spring 2000Triclopyr & 2,4-DBeargrass225 acres

Fall 2000Triclopyr & 2,4-DYarrow35 acres

Fall 2000Triclopyr & 2,4-DBeargrass Huckleberry25 acres

Site Plant

Type

Distance (feet)

# of Samples

Triclopyr (ppm)

2,4-D (ppm)

P Beargrass 121 1 NDa NDa

210 1 ND ND

Q Beargrass 185 – 215 3 ND ND

220 – 240 3 ND ND

250 – 285 3 ND ND

Huckleberry 185 – 210 3 NDa NDa

220 – 235 3 ND ND

245 – 260 3 ND ND

S Yarrow 20 – 23 3 NDb – 0.24 NDb – 0.20

100 – 150 4 ND ND

ano detectable amount. MDL is 0.05 ppmbno detectable amount. MDL is 0.10 ppm

Results of sampling for off-site movement

Dissipation Sampling SitesDel Norte County

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O

N

R

N0.8 0 0.8 1.6 2.4 Miles

Spring 2000Triclopyr 2,4-DBeargrass25 acres

Spring 2000Triclopyr 2,4-DBeargrass66 acres

Fall 2000Triclopyr 2,4-DYarrow Huckleberry116 acres

Dissipation Sampling SitesHumboldt County

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Tectah Creek

Mettah Creek

T

2000 0 2000 Feet

N

Fall 2000Tricloypr 2,4-D

Manzanita44 acres

Dissipation of Triclopyr

0

1

2

3

4

5

6

7

0 1 7 9 13 14 16 28 31 43 62 65 91 146

Days after application

Tri

clo

pry

co

nc

en

tra

tio

n (

pp

m)

BeargrassHuckleberryYarrowManzanita

Dissipation of 2,4-D

0

1

2

3

4

5

6

7

0 1 7 9 13 14 16 28 31 43 62 65 91 146Day after application

2,4

-D c

on

ce

ntr

ati

on

(p

pm

) BeargrassHuckleberryYarrowManzanita

Hupa & Karuk Water Monitoring