Lygus hesperus Nymphs
Recent Advances in Lygus
Management
ESA - Paper #TMP0190
26 October 2003
3:12 PM
Peter C. Ellsworth
&
Yves Carriere
Department of Entomology
University of Arizona
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Lygus Reduce Fruiting Sites
3 Sprays
Untreated
Treated
Note height difference
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Insecticide Use in AZ Cotton
• Selective technologies have helped to stabilize & reduce
usage overall (i.e., Bt cotton & whitefly IGRs in 1996)
• However, current usage reflects the importance of Lygus
Whitefly
Pink bollworm
14
12
10
8
2
0
Major Threat to Cotton
Production in AZ
• Over the last 5 years…
• 45% of all insecticide sprays have been
targeted at Lygus
$217
$106
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Other
$113 (ave. cost / A)
$138
$121
$111 $108
6
4
Lygus bugs
0 Sprays
$68
• 41% of the entire insecticide budget has
been invested against Lygus
$103
$56
$62
$64
$37
• 66% of the yield loss has been attributed
to Lygus
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
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1
Studies Identified Effective Compounds
> 10-fold Increase in Yields (02F4L)
(5-fold increase in yield)
Yield in bales per acre
1.4
5-fold Increase in Yields (98 F4W)
Orthene 90S
Orthene 97
Vydate CLV
Regent
Program (3X)
Must & Thio
Lann & Thio
Thiodan 3E
Legend
C293343-H
C293343-L
UTC
1.2
a
a
1
abc
0.8
c
0.6
d
d
Control
de
0.4 bales)
(0.11
ef
Lint (bales/A)
0.5
1
1.5
2
2.5
0.2
f
f
3
0
Cx x C T VO
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53
35
2
R = 0.86
• Maximum Yield @
1.7 nymphs / 100
0
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13 Adults
+
4 Nymphs
(17:4)
0.5
-0.5
x r2 r4
0 <== ave. costs
1.5
1
Neonicotinoids
Sampling & Thresholds
Yield & Revenue : Density
60
(1.28 bales)
d
0
104 87
Orthene
bc
• Maximum Revenue
@ 5.2 nymphs / 100
-1
is over
• Recommendation:
4 nymphs with at
-2
least 15 total Lygus
-2.5
per 100 sweeps
-5
0
5
10
15
20 25
30 35
(‘15:4’)
Threshold (in nymphs / 100; 15T)
-1.5
‘15:4’
Spray
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Recent Questions in Lygus
Management
• When should managers discontinue any
further Lygus chemical controls in cotton?
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Timing Late Season Controls
(when should you stop spraying?)
– Late season populations can far exceed thresholds
Lygus
Termination
(LT)
– Square (bud) populations decline as crop cuts-out
LT4
5-Aug
16-Aug
Spray Dates
23-Aug
6-Sep
2 wk < c.o.
1 wk < c.o. 1 wk > c.o.
20-Sep
3 wk > c.o.
LT3
• Can we estimate & characterize inter-crop
effects of Lygus spatially?
– Severe and negative interactions among forage hay
(alfalfa), seed alfalfa, and cotton producers in 19992000
LT2
LT1
c.o. = cut-out or nodes above white flower = 5
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2
Lygus Counts > Cut-out
Total Lygus
Large Yield Difference
Nymphs
90
LT1 << LT2
2.5
02.F4LT
75
2
a
60
1.5
b
45
30
c
d
a
15
LT1
1
d
0.5
b
c
0
Lygus Sprays
LT1 LT2 LT3 LT4 LT1 LT2 LT3 LT4 LT1 LT2 LT3
LT4
02F4LT
b
c
LT3
LT2
c
0
LT4
Lygus Chemical Termination Timing (LT)
4 5
23
DP422BR
early
L
T 3 weeks > cutout,
4 5 sprays, 9/20/02
L
T 1 week > cutout,
3 4 sprays, 9/6/02
4 5
4 5
23
23
DP33B
medium
L
T 1 week < cutout,
2 3 sprays, 8/23/02
L
T 2 weeks < cutout,
1 2 sprays, 8/16/02
DP655BR
full
Lygus Chemical Termination X Variety
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Extension
Program
Lygus Nymphs (100 sweeps)
Control of Nymphs is Key!
60
2
3
4
3
4
• Initiated in 2000 in
response to extreme
and negative
interactions among
producers of different
crops
• Communication /
Awareness
• Education
• Systematic Survey /
Research
4
50
40
30
20
Nymph
reductions
related to
yield gains
in LT2
10
0
17-Aug 24-Aug 31-Aug 7-Sep 14-Sep 21-Sep 28-Sep
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Spatial Study
Focal Cotton Fields (50)
• Two townships, spring &
early summer hosts (April July)
Focal cotton field
Seed alfalfa
Forage alfalfa
Cotton
Fallow
• Cotton, alfalfa, seed alfalfa,
fallow, weeds, and small
grains; georeferenced
0.75 km
• Sweeps (15 in. diam.) from
each potential host weekly
• Examine source / sink
relationships among crops
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3
Ring Analyses of Area &
Distance Effects on Lygus
Mean Lygus Density (adults & nymphs)
• Around focal cotton fields, estimate area of
different crops within each 0.75 km concentric
ring
Crop Type
Seed Alfalfa
– Area of unidentified & unknown crops similar for each
ring (ca. 21%)
• Each crop’s area within a ring is multiplied by the
mean density of Lygus; Estimate of source
potential
• Estimate the association between Lygus density
in focal fields and the source potential of each
crop type
Forage Alfalfa
9
Lygus Density
(log D + 1)*
1.50a
34
1.45a
N
Fallow
3
1.44a
Cotton
72
0.69b
* Values fb same letter not significantly different (P > 0.05)
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Source : Sink Effects
Ring
Crop Type
1) 0.75 km
Seed Alfalfa
Coefficient from
Multiple Regression
-6 2
(x 10 )
1.1**
Forage Alfalfa
0.01
Fallow
Cotton
0.008
-0.58*
2) 0.75 - 1.5 km Seed Alfalfa
Forage Alfalfa
• Cotton fields are sinks for
Lygus. This effect
disappears beyond 0.75 km.
0.7*
0.2
Fallow
0.04
Cotton
0.1
Lygus Associations
• Seed alfalfa fields are
sources of Lygus for cotton
fields. This effect does not
extend beyond 1.5 km.
• Strategic placement of crops
could help alleviate Lygus
problems.
no significant associations in rings 3 & 4; * P = 0.06; ** P < 0.001
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Strategic Planting
Acknowledgments
Sensitive host
Non host
1.
• Virginia Barkley who supervised and others (7)
who conducted the sampling
• Christa Ellers-Kirk for assistance with analyses
• Larry Antilla, Jerry Kerr and the rest of the
ACRPC staff who provide crop maps &
coordinates
• Steve Husman, Dave Langston, Jennifer Jones
and cooperating growers involved with the
implementation of the Maricopa Community Wide
Lygus Action Plan
• ACGA and Cotton Incorporated who supported
(pce) the Lygus termination studies
m
5k
Source
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4
Information
• All University of Arizona
crop production & crop
protection information is
available on our web site,
A
C
I
S
• Arizona Crop Information
Site (ACIS), at
• http://ag.arizona.edu/crops
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