Monday, June 24, 2019

Current Alabama Cotton Insect Situation

During the past 7 days, I have traveled from Auburn south thru Troy, Elba and Samson; west to Tallassee, Prattville and Autaugaville; north to Belle Mina in the Tennessee Valley and northeast to Centre and Gadsden. We have some cotton fields that are growing, beginning to bloom and look promising.  However, we have many fields that are late(about 2-3 weeks behind where we would like to be maturity wise), with very poor stands or either with cotton in the same row 2-3 weeks different in maturity. These fields have a long way to go to produce a decent yield. Furthermore, they are going to be difficult to manage from many aspects: weed, PGR and insect management, defoliation and harvest. No two fields on many farms will need the same input at the same time. I am sorry to say that we are going to have to make this crop one field and one week at a time.

Insect wise, we still have plants with heavy thrips damage that may be as mature as the 9th node. However, these plants are growing and I would suggest we focus on other pests now, such as plant bugs. We have anywhere from about a half treatment level to more than a threshold of adult plant bugs in many fields. Many of these fields are setting less than 80% of the fruiting sites. However, after doing some plant mapping and hands on observations last week, I do not believe all of this square loss is from plant bugs. I believe some of these fruiting sites were lost due to the weather and physiological shed. However, we know that these plant bugs are depositing eggs that will produce immature plant bugs in a couple of weeks. Therefore, I would treat fields that have one-half or more of the threshold level of plant bugs and less than 80% square set. Our threshold for adult plant bugs in 8/100 sweeps or 2/25 sweeps. If no sweep net is available, treat with the pinhead square set is less than about 80%.

We have several chemical choices or combinations to choose from. The presence of aphids, which are beginning to appear in some fields, may dictate the chemical choices. Centric is a good choice for both tarnished plant bug(tpb) and aphids. An option would be bifenthrin and imidacloprid(Admire Pro). After first bloom, Bidrin comes back as an option for adult plant bugs and can also be tank mixed with imidacloprid. After first bloom, we may also begin to see immature plant bugs, that have hatched in the field. In fact, we have already observed immature plant bugs in some of our oldest cotton. Under high tpb pressure, Diamond is an excellent tool as a tank mix with products we have mentioned already for adults. Diamond at 6-9 g/acre will give 2-3 weeks control of the hatching tpb nymphs.

Several fieldmen have now reported clouded plant bugs in the mix. Both brown and green stink bugs are also present in many fields, along with the plant bugs. Stink bugs prefer bolls about 10 days old, but when they are not available they will feed on small bolls as soon as the bloom drops off. Stink bugs will need to be controlled along with plant bugs once cotton begins to bloom. Stink bugs do not feed on squares.

Spider mites are also present in many fields at low levels. As long as we are in the thunderstorm weather pattern, I would not worry about spider mites, but instead focus on plant bugs and stink bugs. Remember that no two fields may need the same management or inputs at the same time.