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.