Northwest
Plains
Pest Management News
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| Volume 1 Issue 10 |
Bailey
and Parmer Counties
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August
16, 2002
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Northwest
Plains
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Current Crop Conditions With most cotton well past cutout heat unit accumulation should be monitored to be better able to make pest management decisions. Once 450 heat units have been accumulated since cutout (5 nodes above white flower) the crop is safe from fruit feeding caterpillars. Area cotton being monitored with the Cotman computer model is ranging from 161 to 414 heat units since cutout. Using historical weather data Cotman projects August 18 th to September 2 nd for these fields to reach the 450 heat unit mark. Silage cutters and trucks have started moving around in preparation for harvest. If the historical rain pattern holds true it will start raining about two to three days after the choppers begin to run. With the current dry road conditions the trucks will have the roads powdered up shortly. Caution should be exercised as visibility and handling will be affected. Younger more inexperienced drivers starting back to school need to be reminded of these hazards. Daily Water Requirements
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Bollworms / Headworms Heavy egg lay started in crops other than corn around August 8 th and has continued to present. The bulk of the hatch started August 14th. 2500 to 30,000 small worms per acre have been found in area cotton. The heaviest infestation is in taller more lush cotton. Bollworms
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Headworms Because many young headworm larvae die naturally, do not apply insecticide until they are at least ½ inch long. The economic injury level is about 1 to 2 larvae per grain head of commercial sorghum. Fewer larvae per grain head may justify treatment on sorghum grown for seed because of the higher per-acre value. Inspect at least 30 grain heads from a field to ensure reasonable reliability of sample size. Fall Armyworms Fall
armyworms are being found among the bollworm population. Caterpillars
grow to about 2 inches long and are marked with Aphids Aphids continue to build in area cotton. It is not uncommon to find 5-10 aphids per leaf. This number is far from threshold but should be monitored. Beneficial numbers have been reduced in fields that have been treated for bollworms, which will increase aphid development. |
A total of 60 leaves divided between the top, middle and lower portion of the plant should be sampled from plants across the field to determine actual infestation levels. Insecticidal control of cotton aphids should be delayed until infestations exceed 50 aphids per leaf. Producers in the Lubbock area have been using Intruder at 0.6 ounces per acre with excellent results. The 0.6 ounce rate of this product is comparable in price to Furadan.
Monti Vandiver |
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| Educational programs
conducted by Texas Cooperative Extension serve people of all ages regardless
of socioeconomic level, race, color, sex, religion, handicap or national
origin. The information given herein is for educational purposes only.
References to commercial products or trade names is made with the understanding
that no discrimination is intended and no endorsement by Texas Cooperative
Extension is implied.
The Texas A&M University System, U.S. Department of Agriculture,
and the Commissioners Courts of Texas Cooperating
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As
cotton matures the threshold for bollworms can be extended. Counts that
average 8000 to 12000 small worms per acre on this more mature cotton
can be used. However, if 450 or more heat units have accumulated since
cutout a treatment may not be justified at all. This stage of cotton is
safe from the small worms.
stripes
along the sides. The top of each abdominal segment is marked with two
pairs of black dots from which stiff hairs arise. The front of the dark
head capsule is marked with a pale colored upside-down "Y."
Dr. Jack Bacheler from North Carolina has conducted some pyrethroid
comparisons for control of fall armyworm. The pyrethroids were Karate,
Scout, Capture, Ammo, Baythroid and Asana. His tests revealed that Karate
and Capture were the best. Baythroid and Asana provided the poorest
control and Scout and Ammo were in between. 
