Wednesday, June 16, 2021

Tarnished Plant Bugs on the Move in Alabama

Over the past few days, we have been hearing reports and have seen infestations of tarnished plant bugs 
infesting cotton fields across Alabama, from the Florida line, through central Alabama up to the Tennessee Valley. In some cases, cotton is older (up to 12 nodes) but in many fields the cotton is just starting to put on pinhead squares (7-8 nodes). The one thing all of the fields have in common is that is the most mature cotton in the area. These are the fields we need to be keying in on when scouting. It will be important to scout with a sweep-net (TH= 2 adults per 25 sweeps) and monitor pinhead square retention in the upper 2-3 nodes (maintain 80% of first position squares). Depending on timing, we may see high plant bug numbers and good square retention. However, this could likely be because plant bugs had just moved in and squares that have been fed on have not yet had time to show symptoms. Thus, if either threshold hits, action should be taken. Keep in mind that thresholds aren’t always a “cut and dried” number. If the sprayer won’t be back in an area for 7-10 days and square retention is approaching (but above) 80% with plant bugs present, treatment may be warranted. Sometimes making the call requires some professional judgement based on previous experiences. We filmed a video with more info on plant bugs with Eddie McGriff last year (link).

Based on our sampling of wild hosts (daisy fleabane),
it is likely that we see an extended migration of adult plant bugs over the next few weeks. This gives us the potential to need multiple applications to control adult plant bugs pre-bloom. If this is the case, it will be even more important to monitor square retention. Sometimes following up on an insecticide application can be tricky. We may scout a field 7 days after treatment only to find the same number of (or more) adult plant bugs in the field. This may not mean treatment failure, but that more bugs have migrated into the field. By monitoring square retention, we can check to see that the pinhead squares present at application were protected by the treatment.

Another thing to consider is that the adult plant bugs are also lay eggs and immature plant bugs will start showing up just prior to or at first bloom. Action taken on this migrating population of adult plant bugs can help to reduce future populations of immature plant bugs later in the year.

With good cotton prices and an already late crop, we need to be sure we are staying ahead of insect issues and avoiding any more delays in maturity or losses yield.

If anyone has any observations of plant bugs or any other pests infesting fields, please let myself (662-809-3368) or Ron (334-332-9501) know. We are always here to help.