To: Georgia Cotton Counties
Dear Co-Workers;
COTTON SITUATION:
The Georgia Weekly Weather and Crops Report for the week ending June 4th listed the crop as 90 percent planted and 14 percent squaring. Forty-one percent of the crop is listed in poor to very poor
condition.
INSECT SITUATION:
Tobacco budworm eggs and small larvae are being reported in the southern part of the state. Spotty infestations of plant bugs have also been observed. Thrips numbers have decreased but are still causing damage in some fields. Millions of false chinch bugs are infesting some fields.
Tobacco Budworm:
The first generation of tobacco budworm (TBW) is infesting cotton in the southern part of the state. Most infestations are being found on older, squaring cotton which is typical for this time of year. Infestations have been somewhat spotty but egg counts up to 30% have been reported. Scouts should be making egg and larval counts at this time. Bt cotton should provide good control of TBW. In many situations, beneficial insects will suppress June TBW below economic levels. High numbers of beneficials, especially big-eyed bugs, have been observed in fields I have visited. Every effort should be made to conserve natural controls. Our recommended threshold is 7-8 larvae per 100 terminals prior to the first insecticide spray. This threshold is somewhat conservative and many growers have raised thresholds in June to 10-15 small larvae per 100 terminals when good numbers of beneficials are present. If beneficials are high, the use of an elevated threshold has been effective in most situations. However, one must be prepared to react if beneficials fail to control small larvae. For example, if 12 small larvae were observed on Monday, along with high numbers of beneficials such as big-eyed bugs and minute pirate bugs, one could delay treatment until the field is scouted again on Thursday. If beneficials are suppressing TBW, no (or very few) large larvae will be observed. However, if large larvae (1/4 inch in length which are 3-4 days old) are observed, the grower must be prepared to react immediately. With this strategy there is increased risk but also potential to eliminate early insecticide sprays. If treatment is required, a selective insecticide that will conserve beneficials should be used. Pyrethroid use should be minimized at this time for two reasons. First, pyrethroids are detrimental to beneficial populations and second, we must be concerned about potential problems with pyrethroid resistant TBW. Early exposure of TBW to pyrethroids will select for the resistant populations we may encounter later in the season.
Plant Bugs: Scott Brown in Colquitt County and Eddie McGriff in Decatur County have reported some problems with tarnished plant bug. Typically, we would not expect major plant bug problems during a
dry spring. However, damage is occurring in some fields. Treatment decisions for plant bugs should be based on several factors including small square retention, plant bugs observed in the field, total fruit set, and
variety. Insecticide may be warranted if square retention rates are below 85 percent and are declining and plant bugs or cotton fleahoppers are observed. Plant bug insecticide applications will reduce beneficial insect
populations and this decline in natural control must be considered. Growers should be very cautious when considering treatment of non-Bt cotton for plant bugs since problems with TBW may be exacerbated due to reduced
beneficials.
False Chinch Bugs: False chinch bugs continue to be found at very high numbers in some fields. Most infestations are comprised of adults at this time. We have had some problems
with stand loss resulting from false chinch bug feeding. Most of this type damage has occurred on cotyledon cotton. Based on observations to date, cotton which has attained 4-5 true leaves and is growing is not being
significantly affected. However, false chinch bugs are "true" bugs with sucking mouthparts and are obviously feeding on the cotton. Thus fields which have high populations should be monitored closely for damage.
Several insecticides have provided good control of false chinch bugs, but reinfestation has occurred in a matter of days in some treated fields. Insects are in search of moisture and cotton is the only source in many fields.
Thrips: Thrips pressure is light to moderate in most areas. Plants should be monitored for thrips until they reach the 4-5 leaf stage and are growing rapidly.
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" Click on "Cotton".
Sincerely,
