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V. Cotton Insects
P.M. Roberts, G.A. Herzog, D.C. Jones, and J.R.
Ruberson
The 1996 season will not only be remembered for the introduction
of transgenic Bt cotton, but also as one of the lightest cotton insect pests seasons in
recent times. A continuing trend towards reduced insect pest pressure has been observed
since the elimination of the boll weevil as an economic pest in Georgia.
Thrips populations were near normal and at planting applications
of in-furrow insecticides generally provided adequate control. Beet armyworms were found
on seedling cotton in late May and June. Populations built to high levels in some areas
and triggered an emergency exemption allowing the use of Confirm and Pirate insecticides
for control of beet armyworm. Hot and dry conditions which are conducive for a beet
armyworm outbreak, persisted in late June and early July. However, populations crashed.
Except in isolated fields, beet armyworm posed few problems for the remainder of the
season.
Plants were stressed by heat and drought in June and square
retention dropped in some areas. Plant bug populations were low and did not appear to be
the cause of the square shed. Plant bugs were not considered a problem by most producers.
Cotton fleahoppers were present in most areas of the state in July. High fleahopper
populations were observed in some fields during bloom, but damage to the crop was minimal.
Aphids never reached economic populations and were eventually controlled by a naturally
occurring fungus.
The first tobacco budworm flight occurred in early June and was
light (unusually light pressure was also observed on tobacco). The second flight, which is
generally expected around the Fourth of July and often is the most difficult to control,
did not materialize. Very few tobacco budworm moths were observed or captured in pheromone
traps for the remainder of the season. Bollworm pressure increased in mid - late July.
Moths appeared to be depositing eggs deeper in the canopy than normal and this behavior
made scouting difficult. Control was good with pyrethroids when timely applications were
made. Bt cotton performed well in most parts of the state. However, supplemental sprays
for bollworm were needed on a portion of the acreage. Increased stink bug damage was
observed in some fields, possibly due to the reduction of broad spectrum insecticides
applied.
Fall armyworms were reported in several areas, but most problems
occurred in southwest and east Georgia. Control of fall armyworm with insecticides was
fair at best. Soybean loopers were a problem in a few isolated areas.
The Boll Weevil Eradication Program continued to make progress
towards making Georgia "weevil free". The 1995 outbreak in Brooks county appears
to be cleaned up. Minimal spraying was needed in this area during 1996. Weevils were
detected in a Dougherty county field in July. BWEP personnel reacted quickly and
effectively to this outbreak, intensifying trapping and spraying efforts to prevent its
spread.
Overall, Georgia farmers harvested an above average crop of 747
lbs lint/A on 1,345,000 acres.
Estimates of Losses and Control Costs |
Rank |
Insect |
Cost of Control |
Damage |
Total |
1 |
Bollworm3 |
$15,540,000 |
$13,983,000 |
$29,523,000 |
2 |
Thrips |
11,250,000 |
0 |
11,250,000 |
3 |
Tobacco budworm1 |
10,350,000 |
0 |
10,350,000 |
4 |
Boll weevil2 |
7,397,000 |
0 |
7,397,000 |
5 |
Fall armyworm |
1,800,000 |
2,148,000 |
3,948,000 |
6 |
Beet armyworm |
1,000,000 |
2,148,000 |
3,148,000 |
7 |
Stink bugs |
525,000 |
2,612,000 |
3,137,000 |
8 |
Plant bugs |
210,000 |
0 |
210,000 |
9 |
Soybean looper |
120,000 |
0 |
120,000 |
10 |
Aphids |
70,000 |
0 |
70,000 |
11 |
Cutworms |
35,000 |
0 |
35,000 |
12 |
Whiteflies |
0 |
0 |
0 |
13 |
Spider mites |
0 |
0 |
0 |
| |
Total |
$48,297,000 |
$20,891,000 |
$69,188,000 |
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0 Estimated average price received $0.72/lb. lint.
1,3 Bt transgenic cotton costs: $32.00/A technology fee plus $1/A seed premium
on 400,000 acres. Seventy-five percent of total costs charged to tobacco budworm
($9,900,00) and 25% to bollworm ($3,300,000).
2 Grower costs of Boll Weevil Eradication Program |
| Information Pertaining to Control of Major Cotton Insect Pests in
Georgia in 1996 |
Insects Control |
No. Acres Needing Control |
No. Acres Treated |
No. of Acres Applic. |
Avg. Cost Per Unit Treated1 |
Yield Loss on Units Treated2 |
Yield Loss on Units
Untreated2 |
Bollworm4 |
900,000 |
850,000 |
1.6 |
$9.00 |
15,400,000 |
4,021,000 |
Thrips |
20,000 |
1,250,000 |
1.0 |
9.00 |
0 |
0 |
Tobacco budworm4 |
50,000 |
50,000 |
1.0 |
9.00 |
0 |
0 |
Boll weevil3 |
1,345,000 |
1,345,000 |
--- |
5.50 |
0 |
0 |
Fall armyworm |
150,000 |
150,000 |
1.0 |
12.00 |
2,000,000 |
984,000 |
Beet armyworm |
50,000 |
125,000 |
1.0 |
8.00 |
500,000 |
2,484,000 |
Stink bugs |
125,000 |
75,000 |
1.0 |
7.00 |
750,000 |
1,862,000 |
Plant bugs |
40,000 |
35,000 |
1.0 |
6.00 |
0 |
0 |
Soybean looper |
10,000 |
10,000 |
1.0 |
12.00 |
0 |
0 |
Aphids |
10,000 |
10,000 |
1.0 |
7.00 |
0 |
0 |
Cutworms |
5,000 |
5,000 |
1.0 |
7.00 |
0 |
0 |
Whiteflies |
0 |
0 |
0 |
--- |
0 |
0 |
Spider mites |
0 |
0 |
0 |
--- |
0 |
0 |
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1 Including application costs.
2 Yield units measured in pounds of lint.
3 Grower costs of eradication program. All cotton produced in Georgia is
required to
participate in the Boll Weevil Eradication Program. The annual per acre
assessment for
participation equaled $5.50 per acre. A minor outbreak of boll weevil was
detected
and treated in Dougherty County. Ninety nine boll weevils were captured in
traps and
infestations were confined to 1,500 acres.
4 Does not include costs of Bt transgenic cotton; foliar sprays only. |
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