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COTTON PEST MANAGEMENT NEWSLETTER #3
To: Georgia Cotton CountiesDear Co-Workers; COTTON SITUATION: The Georgia Weekly Weather and Crops Report for the week ending June 11th
listed the crop as 95 percent planted, 29 percent squaring, and 2 percent setting bolls. These figures are similar to the 5-year averages. Thirty-nine percent of the crop is listed in poor to very poor condition. Scattered rains fell last week, but the State remains dry.
INSECT SITUATION:
Tobacco budworm eggs and small larvae are being reported in squaring cotton. There have also been isolated reports of plant bugs. Aphid numbers are building in isolated areas of some fields. Beneficial numbers, especially big-eyed bugs, are numerous in squaring cotton. The ongoing drought will influence near term insect pest management decisions. As cotton begins to square, scouts should begin looking for tobacco budworm and plant bugs. Both of these pests may potentially reduce square retention and decisions to control each or both will be difficult to make in drought stressed fields. Cotton has the potential to compensate from early season square loss. Recent research indicates that 50 percent square removal for 2-3 weeks did not significantly reduce yield in irrigated experiments. Compensation occurred through greater boll retention higher on the plant and increased fruit on vegetative branches. I want to stress that this was under an irrigated situation and late season moisture is needed for adequate compensation. Potentially, we may see a delay in maturity. Perhaps more important is the fact that high early fruit retention puts more demand on the plant and may potentially cause plants to cutout prematurely. Lower retention (within reason) may even be a benefit by reducing demand on the plant and sustaining plant growth. We still have ample time to set a crop. Decisions to treat dryland fields should be made on a field by field basis. A crystal ball would help here.
Tobacco Budworm:
Light populations of tobacco budworm (TBW) are being observed in squaring cotton. Few fields have required treatment as beneficials have suppressed populations below economic levels. Bt cotton provides excellent control of TBW.
Plant Bugs: Plant
bugs and cotton fleahoppers have been reported in isolated fields. Plant bugs are not a consistent pest in Georgia, but all fields should be scouted and treated on an "as needed" basis. We currently have good numbers of
beneficials in fields and consideration must be given to conserving these natural controls. Plant bug treatments will have a negative impact on beneficial populations.Aphids: Aphid infestations have
been observed by scouts on isolated plants in some fields. In the coming weeks, aphid populations will continue to build and ultimately infest whole fields. During a recent scout school, one of the scouts questioned me
concerning fire ants which were foraging on an aphid infested plant. Fire ants are general predators and are of great value where bollworms are concerned. However, when aphids are present, fire ants will feed on aphid
honeydew which is high in sugar content. Fire ants will actually protect the aphids from other predators in an effort to increase honeydew production. Often we refer to the Good, the Bad, and the Ugly where fire ants
are concerned. The good is that fire ants are valuable predators, the bad is that they tend or "farm" aphids which in turn allows aphid numbers to increase more rapidly in fire ant infested fields, and the ugly is that fire
ants will kill off other predators and reduce feeding on bollworm eggs when honeydew is present. Fire ant populations are typically much higher in conservation tilled fields and hence we typically see aphid populations build
to high numbers a few days earlier in conservation tillage fields. However, once the aphids crash due to a naturally occurring fungus, fire ants again provide good predation of numerous pest species. When all things are
considered, fire ants are one of our most important beneficials. Big-eyed Bugs: I have observed high big-eyed bug populations in squaring fields. We consider big-eyed bugs to be one of our most
important predators. Adults and nymphs have broad heads and large, bulging eyes for which they are named. Adults are silvery gray in color and about 3/16 inch in length. Nymphs appear similar in shape to adults
but lack wings and are generally gray in color. Prey include bollworm eggs and small larvae, whiteflies, plant bugs, aphids, and mites. Big-eyed bugs will also feed on nectar and occasionally plant sap. Eggs are
deposited singly on leaves and are grayish white to pink and "hot dog" shaped. Eggs have been common in squaring fields that I have visited. Eggs hatch in about 5 days and development from egg to adult requires about
three to four weeks. Insect Updates: Check the Cotton Insect Hotline
(1/800-851-2847) for updates on current insect conditions. The Cotton Pest Management Newsletter is also posted on the Internet at "www.gaipm.org" and then click on "cotton."
Sincerely, Phillip Roberts
Extension Entomologist |
