Tuesday, May 17, 2022

Alabama Cotton Insect Situation: May 17, 2022

Phone calls have started pick up over the past 7 to 10 days and grasshoppers and thrips tend to be the biggest insect issues we are hearing about. 

Grasshoppers are primarily a concern in reduced or no-till fields and in lighter, well-drained soils. Unfortunately, we don’t have any thresholds for grasshoppers as damage is sporadic and varies from field to field and year to year. The decision to treat is often based professional judgement or the level of risk a farmer is willing to take. At this point in the year, we are dealing with mixed populations and a fair number of adults in the field. The presence of adults (or winged grasshoppers) is important to note, because they are more difficult to control than the immatures (or wingless grasshoppers). Pyrethroids provide spotty control of adults and our general recommendation is up to 3/4 of a pound of acephate.

Most of the calls on thrips we have been getting revolve around making supplemental sprays in dry areas or in fields with historic spider mite issues. In these situations, we try to use insecticides that are less likely to flare mites, such as Intrepid Edge (3 oz/A) or Bidrin (3.2 oz/A). As far as thresholds, we recommend 1-2 adult thrips (dark brown or black) per plant with immatures present. The immatures are smaller and a yellowish color. Presence of immatures tells us that our at-plant insecticides aren’t providing control. You can sample by using a white Styrofoam cup (or something similar) and knocking plants into the cup then count the number of thrips found. Injury is characterized by crinkling of leaves. This is because thrips are feeding on new leaves still in the furl, which brings up an important point. When evaluating foliar sprays for thrips, often you cannot tell how good a spray did until the next true leaf has opened. In other words, if you spray cotton with one true leaf and the second still in the furl, the second may already be damaged, so the third true leaf would more likely show the protection from the spray. Cotton seedlings are most susceptible to thrips injury through the 4-5th true leaf stage and when not growing rapidly.

Late April planted cotton with no at-plant thrips treatment near Tallassee, AL in 2022.

Alabama is all over the board in terms of growing conditions and soil moisture. We have some fields that had enough moisture to germinate seeds but not enough to establish a stand, while we have also gotten several calls about slugs in soybeans. Storms seem to be so localized that its hard to say where we are and are not getting rains. Hopefully the weather will turn around soon and we can get some good growing conditions and kick the crop off.

As always, if we can ever be of any help, please don’t hesitate to reach out and lets us know.