Monday, July 31, 2017

Late July/Early August Cotton Insect Situation in Alabama

What are we currently finding in Alabama cotton fields? Plant bugs, both the tarnished and clouded species, have finally reached threshold or treatment levels in April planted fields that have not been sprayed. Some level of brown stink bugs can also be found in these same fields. A bug clean up spray would be advised for most cotton that is in the fourth or fifth week of bloom. Peak numbers of squares and bolls are currently at risk. Cotton planted after about May 10 missed most of the plant bugs this season. In central and south Alabama, there are very few plant bugs currently present in wild host or other crops. In other words, there are no more plant bugs in the landscape to migrate to cotton in 2017 in that region.

Between July 24 and 28, numerous field people from all areas of the state were contacted about escape bollworms on cotton with caterpillar technology. As of July 31, no none has reported any problems. We have conventional cotton on research stations in several areas of the state. Some level of bollworms and damage can be found on this cotton. The corn earworm flight from corn began about July 15 and has likely already peaked. Tobacco budworms will enter the mix during the month of August, but they will not be part of the "escape" situation in August. However, fieldmen should continue to monitor closely for escape bollworms. In Alabama, I would suggest we try the pyrethroid chemistry first if escapes are found.

Spider mites came into the picture about the third week of July in the Tenn. Valley area. Mites will likely show up in other fields statewide if we ever experience a 7-10 day period between rain events. Abamectin will provide the most economical control of mites. Whiteflies may occur in late season on our late maturing fields. If whiteflies are observed, I would recommend we use pyrethroid chemistry for stink bugs since Bidrin seems to aggravate the whitefly situation.

We will likely see stink bug numbers increase as we move into August and even September in our late maturing cotton. The southern green stink bug will make up a greater part of the population in coming weeks. This gives us the flexibility to choose either pyrethroid or phosphate chemistry. For weeks 3 through 6~7 of bloom, we recommend a 10% internal damage boll threshold for stink bugs.

Thus far in 2017, insects have not been a major limiting factor in Ala cotton production. Let's hope we can keep this trend going for several more weeks.

Monday, July 17, 2017

Mid-Late July Outlook for Cotton Insects

Tarnished plant bugs (TPB) have been hatching into the immature nymphal stage for about two weeks in April planted cotton. A few immatures are almost to the adult stage. In fact, the first 2017 cotton reared adults were observed in central Alabama today, July 17. Numerous more immature TPBs are still hatching from the egg stage. The point to remember is that the large immatures and adults do most of the fruit damage to cotton. In unsprayed fields, a second generation will begin to develop soon. The first generation was not at threshold or treatment levels in most fields. However, eventually you may have damaging or treatable numbers as the population continues to increase. At this point, you will have an embedded population that contains all stages from eggs to adults. When this situation develops, one insecticide application will not clean up a damaging level. There may even be a place in 2017 for a late July-early August application of the IGR Diamond added to an adulticide.

2017 is going to be different than recent years in controlling TPBs. Both 2015 and 2016 were hot and dry during July, and the plant bug population crashed on their own. Cloudy weather, abundant rainfall, and lush rapid growing cotton is a much better host for TPBs in 2017, resulting in a high level of survival this season. The numbers of TPBs will likely continue to increase until controls are applied. A sub-threshold level in July will lead to numbers and damage well above threshold by early to mid August if left untreated. A high number of TPBs of all ages is difficult to clean up. Don't blame the chemical or consultant or Extension agent when one application does not do the job. Other than Diamond on immatures, no product will give more than 3-5 days of plant bug control.

Part of the current population of plant bugs in central Alabama and as far north as Talladega is the clouded plant bug species (CPB). Both immatures and adults look different than tarnished plant bugs. Immature CPBs are not as green as TPBs. CPBs are more cylindrical in shape and have alternating dark and light bands on their antennae. Damage from both species are the same, and the same chemicals should work on both.

Attached is a picture of a clouded plant bug nymph.