Starting with soybeans, calls have picked up over the past week or so. We are starting to get reports of soybeans loopers in southwest Alabama. Soybean loopers are ferocious foliage feeders that can do a lot of damage in a hurry. Luckily, natural mortality of small loopers is generally very high, and many of the “thread-like” loopers we see will not survive. For that reason, we don’t recommend counting soybean loopers that are less than 0.25-0.5 inches long. The goal of soybean looper (and other defoliator) management is to avoid excessive defoliation. From R1-R6 we want to prevent 20% defoliation, from R6 to R6 plus 7-10 days, we can tolerate up to 30% defoliation. Estimating percent defoliation can be tricky and many people overestimate how much damage has been done. The Crop Protection Network has an excellent tool that you can use to train your eye on defoliation estimates (link). As far as soybean looper counts, our threshold is to treat when 5 loopers are found per foot of row (25 per drop cloth if sampling two rows at a time) or 19 loopers per 25 sweeps. We have plenty of good options for looper control including diamides (Coragen eVo, Besiege, Vantacor) as well as Steward and Intrepid Edge. While pyrethroids provide good control of velvetbean caterpillar, they do not kill soybean looper. We have seen times where acephate can knock back populations for a week or so, but then the loopers comeback with a vengeance. This may be worth trying in very specific situations where loopers are stink bugs are at damaging levels in the late R6 stages.
Speaking of stink bugs, we have started getting reports of
redbanded stink bugs (RBSB) infesting fields in central and south Alabama this
week. RBSB is much more damaging and more difficult to control than our traditional
stink bug complex. Threshold is 4 RBSB per 25 sweeps or 2 per 5 row feet (1
drop cloth sample with both rows). Treatment for RBSB can be terminated at R7
unless there are adverse environmental conditions that would promote poor seed quality.
When the population is primarily made up of immature RBSB, tank-mixtures are
often required. Bifenthrin + acephate is the standard for RBSB control, but
Bifenthrin + imidacloprid is also an option that is more economical if
populations are right at threshold. Vertento is another good option, although
it carries a higher price tag.
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| Adult (left), freshly hatched (middle) and late instar immature (right) redbanded stink bugs. |
Cotton update
Overall, the cotton situation has been light. We have received
a few reports of stink bugs and plant bugs requiring attention, but pressure
has been seemingly low. We also currently feel good about the cotton jassid
situation. To date, cotton jassids have been hard to detect in fields in
southeast Alabama. We currently have confirmed the pest in cotton in Autauga,
Lee and Elmore counties in central Alabama and in Henry, Houston, Dale and Geneva
counties in southeast Alabama. We have also scouted fields in Coffee, Pike,
Barbour and Russell counties but no jassids were observed. While the
distribution of jassids is a little more in Alabama than this time last year,
the size of the populations seem to be lower. The first field treated in
Georgia was also much later this year than last. We will continue to monitor the
situation and provide updates as needed. The biggest thing to consider for now
in cotton in southeast Alabama is that pyrethroids (bifenthrin and others) do
not control cotton jassids and in some cases can make flare them. I would be very
hesitant to spray pyrethroids for stink bugs in the wiregrass due to this.
To see an up-to-date map on cotton jassid detections across
the Cotton Belt, you can check out the Stop two-Spot Cotton Leafhopper
(Stop2SCL) website here (https://stop2scl.org/cotton/)
As always, if we can ever be of any help, or if you would
like to provide input on the situation in your area, please don’t hesitate to
reach out to your local Extension Agent or myself (Scott Graham: 662-809-3368)
and Ron Smith (334-332-9501). For more information on thresholds and
insecticide recommendations, visit the Alabama Cotton IPM Guide (IPM-0415). To stay up-to-date on the Alabama cotton insect situation,
subscribe to the Alabama Cotton Shorts Newsletter,
Alabama Crops Report Newsletter and Podcast,
and the Syngenta Pest Patrol Hotline.
