Blooms are rapidly approaching the tops of plants in many April and
early May planted fields. This is especially true in dryland fields, but is also common in some irrigated fields as well. Obviously, the drought has contributed to early cutout in dryland situations, but there were
questions concerning early cutout in irrigated fields. Early cutout in irrigated fields may be due to several factors, but most likely moisture and temperature stress, in addition to a good early fruit set, have played a
part. INSECT SITUATION: Insect pressure continues to be relatively light in most areas but sporadic problems have been observed in some fields. In most areas, a mixed population of tobacco budworm
and corn earworm moths are being observed. Low populations of fall armyworm have been reported in southwest Georgia. Beet armyworm is sporadic but some late planted cotton has required treatment. Stink bugs are
also more numerous in some late planted fields that I have visited. Aphids have crashed in many areas due to the naturally occurring fungus. Predator numbers remain high in most fields.
Corn Earworm and Tobacco Budworm: Depending on location, the species makeup of corn earworm (CEW) and tobacco budworm (TBW) varies significantly. Scouts should be observant of moths in the field because this will
give some idea of which is the predominant species. Eggs and small larvae of both species appear identical in the field, however, large larvae can be distinguished with the aid of a hand lens by examining the inner surface of
the mandible (mouthpart). TBW has a tooth-like projection or retinaculum. CEW does not possess a retinaculum. We have recently posted some images of TBW and CEW mouthparts on a website at gaipm.org which should help in
distinguishing these two species. Species identification can be of benefit particularly when troubleshooting poor performance of an insecticide.
Large CEW larvae have been reported from some Bt cotton fields in
southwest Georgia. Pressure is light to moderate but some fields have required treatment. Recommended scouting procedures are the same for both Bt and non-Bt cotton. However, scouts should be sure to monitor
blooms and bloom tagged bolls closely in Bt cotton. Scouts should search the top 12 inches of the plant, one bloom, one bloom tagged boll (be sure to look under and in bloom tags for larvae), and one additional boll lower in
the plant. If any damage is observed, the entire plant should be searched for larvae. Control of CEW on Bt cotton is recommended when 7 - 8 large larvae (1/4 inch in length) are found per 100 plants.
Stink Bugs: Be observant for stink bugs, especially in fields which have not been treated with an insecticide that has activity on stink bugs. A significant portion of the cotton acreage falls into this
category. Some fields have been treated for stink bugs. Internal boll damage (stained lint or warty growths on the inner boll wall) has exceeded 30 percent in some fields, but damage may vary significantly from
field to field. As corn continues to dry down and is harvested, we would expect stink bugs to leave these fields in search of new plant hosts.
Fall Armyworm: Early infestations of fall
armyworm have been reported in some southwest Georgia fields. To date, numbers have been fairly low. When larvae are small, identification is difficult. The suggested threshold for fall armyworm is 10-20
larvae per 100 plants (approximately 2X the bollworm threshold). Control of large larvae is difficult. Do not attempt to eliminate an established population of large fall armyworm.
Beet Armyworm:
A few fields have been treated for beet armyworm (BAW). Most reports of BAW have been in late planted cotton, however, larvae have also been observed feeding in blooms. Beneficial populations have been high
for most of the year and have helped suppress this dry weather pests.
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,
