Weekly in-season Updates
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INFORMATION |
July 29, 2007 Talkin’ Cotton Jerry Goodson and I have been getting a lot of calls about aphid control problems on cotton. Some applications have not been effective for aphid control, and resprays of the same product have not helped much. We have inquired into submitting for a section 18 emergency exemption for Furadan, but with the new classes of compounds available, chances are remote for having Furadan available. We have discussed this with other extension entomologists in neighboring states and they have given us some suggestions for dealing with this problem. We really appreciate the assistance of Dr. Roger Leonard, Extension Entomologist for Louisiana for his help. First, it is important that we take advantage of a population of beneficial insects. Jerry has seen high populations of beneficials in areas that have not been sprayed. Aphid populations may be high, but beneficial populations are building. Many times the beneficials will overpower the aphids if given time. Aphids do most of their damage to the cotton when the bolls start opening and lint is contaminated with honeydew. We can tolerate moderately high aphids if beneficials are building, so this should be considered prior to starting a chemical aphid control program. Aphid populations seem to cycle, they build up, peak, and then the population is infested with a fungus that will decrease the population. When the new Neonicotinoid class of insecticides for control of aphids was first introduced, producers were getting control even if they cut rates to the lowest recommended rate, and these rates became the accepted rates for control. Recently these rates quit working as effectively as before. Also producers who have used Orthene or pyrethroids, or who have mixed low rates of the neonicotinoid products with their Roundup have caused an aphid population explosion that is difficult to control. If chemical control is warranted best success in this area involves use of Intruder at 1 oz./A or Centric at 2 oz./A with application volume of at at least 3 gallons per acre if applied by air or 5 gallons per acre if ground applied. Under heavy aphid pressure 5 gallons per acre or 10 gallons per acre spray volume is recommended. A silicone based metholated seed oil should be used to increase deposition on the leaves. The high rate is needed because a low rate applied as the first application will make control more difficult if a second spray is needed. The key to aphid control is to try to let beneficials and the aphid fungus control the population, but if control is needed, concentrate on highest label rates, sufficient spray volume, and a good surfactant to ensure the best possible control.
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