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Texas Cooperative Extension Service The Texas A&M University System Plains Pest Management Newsletter |
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News about Integrated Pest Management in Hale-Swisher Counties. Greg Cronholm, Extension Agent - IPM, 122 East 6th, P.O. Box 680, Plainview, TX., 79073-0680, 806-291-5273 |
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Web Site: http://entowww.tamu.edu |
E-Mail:
g-cronholm@tamu.edu
August 16, 2001 |
Over the past seven days scattered showers have provided relief for may area cotton fields. Reports of rainfall have ranged from 0.2 to 2.5 inches. The cloudy skies, cooler temperatures and high humidity have been factors which contributed to decreased stress, but at the same time may be contributing to increased survival rates for cotton pests. Over the past seven to ten days there has been a continual increase in Lygus populations. Numbers have ranged from light to moderate to extremely heavy. In the heavy fields lygus counts have averaged one to 2 per plant with counts up to 120,000 per acre. The heaviest populations have generally been found in well irrigated fields, especially flat row watered fields. This has not been the case in all situations. One of our ginners at Edmonson reported finding 36 lygus per 3 row feet in a drought stressed cotton field, which is very unusual. Currently we have mixed populations of cotton flehoppers and lygus nymphs. We are not concerned with the cotton fleahopper since they damage squares smaller than 1/3 grown which will not have time to produce a harvestable boll. |
When taking samples remember the cotton fleahopper nymphs are pale green in color and the Lygus nymphs are bright green with darker color antennae. The damage situation from Lygus feeding has changed dramatically since last week. We are now seeing small bolls being shed from cotton, many of which exhibit signs of Lygus feeding. In some well irrigated cotton fields, boll loss has been high due to this pest. A boll damaged by this pest has one or more small black spots on the exterior carpal wall of the boll. When the small boll is cut with a knife the internal area is discolored below the lygus feeding site. Many products are effective in controlling Lygus infestations. Our cotton control guide lists the following products: acephate, Capture ®, Baythroid ®, Leverage ®, Karate ®, Ammo ®, Decis ®, Bidrin ®, dimethoate, AsanaXL ®, Provado ®, Lannate ®, methyl parathion ®, Vydate ®, parathion, Scout x-tra ® and Fury ®. As a group, pyrethroids have generally provided excellent control of Lygus infestations. Coverage is again very important for controlling this pest. We generally encourage applications of 3 gallons of water per acre mixed with a pyrethroid. Currently pyrethroids have been discounted significantly. Check with your chemical distributor or aerial applicator to see which may be the cheapest at this time. Cotton bollworms infestations continue to increase over the area, although not in all fields. The higher populations have been in the well irrigated cotton. Larval sizes have ranged from 1/16 to 5/8" long. Most were in the 1/4 to 3/8 inch range. Counts have ranged from 0 to 35,000 per acre, but have generally ranged from 2,000 to 14,000 per acre. Our threshold for treatment ranges from 8,000 to 12,000 per acre at this point in the season. |
TEXAS
COUNTRY CLEANUP
Cotton|
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The cheaper prices for insecticides has helped to offset our cheap cotton price, which means we can justify bollworm treatments at these thresholds. Bollworm egg lays have also been on the increase and in corn growing areas bollworm/corn earworm moths continue to emerge and move to other crops such as cotton, sorghum and millet. In the Edmonson/Kress areas we have seen an increase in beet armyworm trap collections with an average of 30 per day. The Cotton Center area has been less with an average of 13 beet armyworm moths per day collected. Beet armyworm egg masses have been observed in the Edmonson/Kress area, but we will have to see what impact the beneficials have on these populations. Cotton boll weevil infestations are gradually increasing with more fields now having punctured squares and bolls. Overall our infestations remain much lighter than the previous two years. More area traps are now collecting weevils, which is also in indicator that weevils are increasing. Growers need to continue to monitor this pest up to the time the eradication program starts on September 3. Whiteflies and cotton aphids can still be found in many fields and may become a secondary pest after treatments for Lygus bugs or bollworms. Stinkbugs continue to be found in many fields and may also be a factor in some of our small boll shed. Beneficials remain at fairly good levels in untreated cotton. Crab spiders, red cross beetles, pirate bugs and lacewings have been the most common beneficials encountered. CORN Harvest has started for early planted, short season corn. Recent rains have helped to finish out corn on some farms. Growers are now finishing their last irrigation. Harvest should be in full swing by the last few days of August to the first week of September. Banks grass mites continue to damage more foliage, but many fields still have enough green leaves to complete kernal fill.
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Stalk rots are starting to show up in corn which were induced by drought stress, spider mites or southwestern corn borer. Most of the stalk rots found now are directly the result of drought stress. Lodging from stalk rots should be monitored closely and harvest at a higher moisture may be required to negate harvest losses . SORGHUM Sample sorghum heads for corn earworms and fall armyworm as egg lays continue. Late blooming sorghum should be scouted for sorghum midge daily during the bloom period. This is the time of year midge populations can be very high in this region.
Greg Cronholm,
Extension Agent - IPM,  Posted at this web site by: texagnet Internet Services. |
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