We are now in the home stretch, as far as insect control, in most fields of April planted cotton. Overall, there are a few things that I would be on the outlook for this week.
Stink bugs pose the greatest threat to most fields for the
remainder of the season. Numbers vary greatly from field to field and in many
cases from area to area within fields. For this reason, surveys must be
thorough enough to detect the overall situation in each field. A dozen or so
bolls will not accurately reflect the true infestation in most instances.
Remember to select or sample 10-12 day old (quarter diameter) bolls. First
separate out those with external damage from those with no external feeding
signs. Second, crush those bolls with external damage and observe for internal
injury. Our recommended “dynamic threshold” ranges from 30-50% internal damage
early in the blooming period down to 10% during weeks 3-6 of bloom. This low
threshold corresponds to the period when a high percentage of the total bolls
are being set. Later into the blooming season, which is where many of our
fields are now, we can relax our treatment threshold back up to the 30-50% range.
Now onto some other pests:
The mid-to-late July bollworm flight was maybe the lowest in
modern times. Bollworms have been almost non-detectable in fields in central,
SW and SE Alabama, even in cotton with no genetic technology.
As to tobacco budworms – while at the Wiregrass Research
Center (SE Alabama) last week, numerous TBW moths were observed. This matches
up with reports from SW Georgia that indicates an extremely high budworm flight
going on in that nearby location. This will not be anything of concern for Bt cotton but this could be a very
significant event for peanut growers and even soybeans.
No questions were received concerning spider mite control
last week. However, I personally observed mites in numerous fields that have
not historically had mite infestations. They are present in many fields and
their explosion will be greatly influenced by temperature and moisture for the
remainder of the season. Growers treating for stink bugs would be wise to
select an insecticide that is least likely to help flare mites.
With these thoughts we will end today and get back with
another update as conditions change.