Cotton Insect Update: July 10, 2015

Tarnished plant bug populations have continued to be high over the last couple weeks in the Delta. A lot of the cotton is at or near the bloom stage when it is most attractive to plant bugs.

If you remember back in the spring, pretty much all of the corn and over a million acres of soybean were planted in about a 2 week window when we had optimum planting conditions. All of that corn is at or beyond the soft dough stage and all of those soybean are no longer flowering and are starting to fill pods. At those stages, corn and soybean are no longer attractive to plant bugs and they are looking for a suitable host for reproduction.

As a result, we have basically been in a “perfect storm” kind of situation for plant bug infestations in cotton. Roughly 2 million acres of corn and soybean have been supporting plant bug populations for the last month and they have been moving out of those crops into cotton. This is compounded by the fact that we have fewer acres of cotton for those plant bugs to go to, so they are becoming more concentrated.

From a management standpoint in cotton, it is time to start getting out the Diamond applications if it has not already been applied. Also, as we move into bloom it is best to start using tank mixes or premixes of organophosphates and pyrethroids. In most of our tests every year, the best control of plant bugs is usually three quarters of a pound or more of acephate mixed with 5-6 ounces of bifenthrin. Premixes such as Bidrin XP (Bidrin plus bifenthrin) can also be a good option at this time. It is also important to make the switch at this time because most of the sprays up to this point have consisted of either neonicotinoids (Centric, Admire Pro, or other imidacloprid-based products) or Transform and they need a break to minimize the chance of developing resistance to those insecticides.

Although the premixes and tank mixes are often or best option for controlling high populations of plant bugs in blooming cotton, those sprays come with some baggage. Most notably, those sprays are highly likely to flare other pests such as cotton aphid and spider mites.

Several spider mite sprays have started across the state. The most important thing to remember is that we have seen some resistance to abamectin the last couple of years. We have already heard of cases this year where abamectin resulted in poor control of spider mites in cotton. If you choose to use one of the abamectin-based products, make sure that they are used at the upper rate range. Also, control of spider mites is one of the pests that we can see improved control with the use of a surfactant. If you are not willing to risk an application with abamectin, one of the other miticides such as Portal or Zeal should provide good control of spider mites.

Finally, as the corn dries down, we will likely start seeing some eggs in cotton. In many situations, we see an economic benefit of foliar sprays on both Bollgard II, Widestrike, and TwinLink cottons when moderate to heavy bollworm infestations occur.