Managing Thrips in Seedling

Cotton with Starter Fertilizer and a

Single Foliar Application

Michael Toews

The University of Georgia

Department of Entomology

Tifton Campus

M. Toews, P. Roberts, J. Herbert, S. Tubbs, G. Harris, B. Srinivansan,

R. Smith, J. Greene, J. Bacheler, D. Reisig, A. Herbert

Background

• Thrips are the most

consistent insect pests of

SE cotton production

– Damage includes leaf

curling, delayed maturity,

loss of apical dominance

and stand loss

– Loss of aldicarb is driving

thee need for alternatives

– Damage is most intense

under conventional tillage

with planting dates before

May 12

1 mm

Background

• University generated

data show:

– Neonicotinoid seed

treatments by

themselves are

inadequate for early

planting and

conventional tillage

– Repeated foliar

applications will lead to

insecticide resistance

and secondary pest

outbreaks

Research Objectives

• Evaluate efficacy of potential foliar insecticides for managing thrips in seedling cotton

• Examine how a seed

treatment in combination

with starter fertilizer and a

well timed foliar

application may mitigate

thrips injury

– Determine the optimal

timing for the single

foliar application

• Examine strip tillage and

how it affects thrips

populations

• Response variables

reported here:

– Counts of immature

thrips

– Above ground plant

biomass

– End of season lint

yield

Experimental Methods

• All trials (AL, GA, NC,

SC, and VA) planted in

April under conventional

tillage

• Insecticide trials

(fungicide treated PHY

375 WRF) were sprayed

twice with high rates of

Benevia, Dimethoate 4,

Karate Zeon, Lannate 2.4

LV, Orthene 97, Radiant

SC or Vydate C-LV

• Independent starter

fertilizer trials (10 gal 10-

34-0) were conducted

under irrigated and

dryland conditions

• Both starter trials

(fungicide + Cruiser

treated PHY 375 WRF)

received foliar applied

acephate at 90% 1st true

leaf bud or at second true

leaf

Insecticide Trials: Immatures

Benevia

Dimethoate 4

Karate Zeon

Lannate 2.4 LV

Orthene 97

Radiant SC

Untreated

Vydate C-LV

Imm

atu

res p

er

5 p

lan

ts

0

25

50

75

100

A

AB

BC

CC

D DD

P < 0.01

Insecticide Trials: Biomass

Benevia

Dimethoate 4

Karate Zeon

Lannate 2.4 LV

Orthene 97

Radiant SC

Untreated

Vydate C-LV

Pla

nt

bio

ma

ss (

g)

0

3

6

9

12

AA AB

ABAB

BC

DC

D

P < 0.01

Inverse

correlation between

biomass and

immatures P< 0.01

Insecticide Trials: Lint

Benevia

Dimethoate 4

Karate Zeon

Lannate 2.4 LV

Orthene 97

Radiant SC

Untreated

Vydate C-LV

Lin

t (lb

pe

r a

cre

)

0

300

600

900

1200

A AAB AB ABAB

ABB

P < 0.01

Inverse

correlation between lint

and immatures

P = 0.22

Yield equals cumulative

plant stress!

Starter Trials: Immatures

None 1st Leaf 2nd Leaf

Imm

atu

res p

er

5 p

lan

ts

0

10

20

30

40

50No starter

Starter

Starter P = 0.54Foliar P < 0.01

None 1st Leaf 2nd Leaf

0

10

20

30

40

50No starter

Starter

Starter P = 0.52Foliar P = 0.06

Dryland Irrigated

Starter Trials: Biomass

Dryland Irrigated

None 1st Leaf 2nd Leaf

Pla

nt bio

mass (

g)

0

7

14

21

28

35No starter

Starter

Starter P = 0.28Foliar P = 0.89

None 1st Leaf 2nd Leaf

0

7

14

21

28

35No Starter dry

Starter

Starter P = 0.02Foliar P = 0.01

Starter Trials: Lint

Dryland Irrigated

None 1st Leaf 2nd Leaf

Lin

t (lb

pe

r a

cre

)

0

300

600

900

1200

1500No starter

Starter

Starter P = 0.99Foliar P = 0.71

None 1st Leaf 2nd Leaf

0

300

600

900

1200

1500No starter

Starter

Starter P = 0.83Foliar P < 0.01

Discussion

• Insecticide trials

– Benevia and Radiant SC

provided similar levels of

immature suppression to

Orthene 97

– The pyrethroid provided

very little immature

suppression and performed

poorly relative to other trts

– Generally speaking, plants

receiving two foliar

treatments developed less

biomass than plants with a

seed treatment only

Discussion

• Dryland starter trials

– No obvious advantage

to use of starter

fertilizer

– Inconsistent

differences attributed

to foliar applied

insecticides

– Trials received little

rainfall for the first 60

days

• Irrigated starter trials

– There was a

measurable increase

in plant biomass when

using starter fertilizer

– Application of foliar

insecticide at 90% first

true leaf bud provided

optimum thrips

suppression

Strip Tillage Work

• Experiments were

conducted in 2008-2009

at Tifton, GA

– RCBD (2 x 3 factorial

arrangement) with 4 reps

(8-row by 45’)

• Conventional tillage vs. strip tillage

• Winter cover crops

(crimson clover, wheat, or rye)

– Cotton (DP 164 B2RF) was

planted during 1st wk of

May

Results: Species Composition

2008 2009

Su

m a

du

lt th

rip

s

0

100

200

300

400F. fusca

F. occidentalis

F. tritici

Other spp.

Co

nve

ntio

na

l

Co

nve

ntio

na

l

Str

ip

Str

ip

662 adults

931 immatures

179 adults

383 immatures

85.4% F. fusca, 8.8% F. occidentalis, 4.5% F. tritici, 1.3% other spp.

All Thrips per 5 Plants

0

14

28

42

56 Conventional

Strip

2008 2009

0

14

28

42

56

All

thrips p

er

5 p

lants

0

14

28

42

56

AB

A B

A

B

AB

A

BA

B

Dotted lines designate

the extension recommended foliar

treatment threshold of 2 to 3 thrips per plant

14 DAP

21 DAP

28 DAP

There were no tillage by

cover crop interactions, and there were no

significant differences among cover crops

Percent Ground Cover

2008 2009

Pe

rce

nt g

rou

nd

co

ve

r

0

20

40

60

80

100Conventional

Strip A

A

B

B

There were no tillage by

cover crop interactions in either year

In 2008 only, there was

more ground cover in wheat and rye than

crimson clover

Discussion

• Why were thrips

populations 1/3 smaller in

2009 compared to 2008?

– Temperature: in 2008 there

were 415 dd above 15.6º

C, compared to 411 dd in

2009

– Rainfall: in 2008 there was

a total of 4.9 cm (5 events)

compared to 17.0 cm (16

events) in 2009

• Across variable

conditions, thrips counts

exceeded the foliar

threshold in all but one

sample date in

conventionally tilled plots

– Data suggest that seed

treatments and

conventional tillage did not

provide enough protection

for early planting windows

– Seed treatments and strip

tillage did provide the

required protection

Acknowledgements

• Technical support: David Griffin, Corey Thompson, Annie Horak, Dan Mott, Sean Malone, Steven Roberson, Jess Samler

• Funding: Cotton Incorporated

• Product donations: Amvac Chemical Corp., BASF, Bayer CropScience, DuPont, Dow AgroSciences, Monsanto Co., and Syngenta Crop Protection

email: mtoews@uga.edu, webpage: www.ent.uga.edu