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COTTON PEST MANAGEMENT NEWSLETTER #7July 13, 2000 COTTON SITUATION: The Georgia Weekly
Weather and Crops Report for the week ending July 9th listed the crop as 80 percent squaring and 43 percent setting bolls compared with the 5-year averages of 89 percent squaring and 43 percent setting bolls. Scattered
rains were welcomed, yet some areas continue to be under drought stress. Some dryland fields have bloomed out the top.INSECT SITUATION: Aphid populations are crashing due to a naturally occurring fungus in
many parts of the state. Corn earworm activity is increasing in the southern part of the state and we would expect this to continue as corn dries down. Tobacco budworm are also still present. Low populations of
fall armyworm have been reported and beet armyworm activity has increased. Stink bugs are also being observed in fields at this time. Aphids: Aphid infestations have crashed in southwest Georgia and reports of
aphid decline are also being reported in other parts of the state. Aphids appeared to be more of a problem this year compared with recent years and damage may have occurred in some fields. Severely infested fields have
dropped some leaves on the lower part of the plant. If aphids have not begun to crash in your area, be sure scouts are watchful for the naturally occurring fungus which is associated with grayish fuzzy aphids.
Once the fungus is detected in a field, we would generally expect the population to crash within a week. Results of an aphid fungus sampling survey in Georgia may be viewed on a University of Arkansas web site at
(http://www.uark.edu/misc/aphid). This website will show the presence or absence of aphid fungal infection for aphid samples submitted from various parts of the state. Corn Earworm: As corn begins to dry
down, we expect to see an increase in corn earworm (CEW) activity in cotton. We have received reports of both small and large larvae in blooms and under bloom tags in Bt cotton. Bt cotton offers excellent control of
tobacco budworm but supplemental treatment of CEW may be required. Scouts should be paying close attention to blooms and bloom tagged bolls at this time.Tobacco Budworm: Tobacco budworm (TBW) eggs and small larvae continue to be reported in central
Georgia and a mix of CEW and TBW have been observed in southwest Georgia. FMC has been running egg test to identify TBW:CEW species makeup in Alabama and Georgia. On July 6, egg assays indicated 62-94 percent of the
eggs assayed in Dooly and Sumter Counties were TBW. As a whole TBW pressure has been light to moderate to date.Beet Armyworm: We have received several reports of scattered beet armyworm (BAW) infestations in
cotton. BAW is a dry weather pest and thus conditions have been conducive for their establishment. Infestations have been most common on late planted cotton. Confirm insecticide, manufactured by Rohm and Haas, is
now labeled on cotton and should be added to the cotton insect control recommendations for BAW. Beneficial insects play a vital role in suppressing BAW infestations.Fall Armyworm: Scattered populations of
fall armyworm have been reported. To date, infestations have been light.Stink Bugs: As cotton begins to set bolls, scouts need to be monitoring for stink bugs and their damage. In the last week, several
stink bugs have been observed in cotton and decisions to treat should be based on thorough scouting. Stink bugs are most likely to become an economic problem on fields which have not been treated with an insecticide that has
stink bug activity such as pyrethroids. Treatment is recommended when stink bugs exceed 1 per 6 row feet or when 20% of small bolls display internal signs of feeding and stink bugs are observed in the field. When using
a drop cloth be sure to shake plants vigorously to dislodge stink bugs. Additionally, plants should not be disturbed when placing the cloth in the row middle. After shaking the plants, count the bugs quickly. It
is also a good idea to look under the cloth when leaving a sample site because stink bugs may have dropped from the plant when the cloth was placed or quickly crawled under the cloth while the plants were being shaken.
During 1999, we began recommending the use of internal boll damage as an additional means of scouting stink bugs. To determine internal boll damage, scouts should randomly pull bolls which are approximately the diameter of a
quarter. Selected bolls should be soft enough to be easily squashed in your hand. The inside of the boll should be examined for damage which would include yellowing or stained lint and/or warty growths on the internal
boll wall. Recommended treatments for stink bugs include Bidrin, methyl parathion, or pyrethroids. Pyrethroids would be the treatment of choice if CEW or FAW are also present in the field. 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 |
