Managing Thrips in Seedling Cotton with Starter Fertilizer ... · • Why were thrips populations...
Transcript of Managing Thrips in Seedling Cotton with Starter Fertilizer ... · • Why were thrips populations...
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: [email protected], webpage: www.ent.uga.edu