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.
