We are beginning to see the “light at the end of the tunnel” for most of our late planted cotton across Alabama. We visited several fields in central and south Alabama this week and the crop looks good. Many fields in south Alabama were beginning to bloom out the top and are pretty much safe from bugs. There are still many fields at risk from plant bugs and stink bugs, however, so we can’t walk away yet.
Plant Bugs
Plant bugs are still heavy and requiring treatments in many later
planted fields. For a lot of the crop however, its time to talk about plant bug
insecticide termination. Recent research from the mid-south entomologists
groups suggest cotton is “safe” from plant bugs once it reaches Node Above
White Flower (NAWF) 2 or 3. Regardless of the plant bug populations in these fields,
they are not doing economic damage and should not be sprayed. In our younger
fields, plant bugs are absolutely doing damage and should be monitored and
treated when threshold is reached.
Stink Bugs
Internal boll injury has made a big jump this week. On our
research farms in Prattville, Headland and Belle Mina plots that had not been
sprayed with a stink bug material had as high as 50% internal boll damage, even
though we are not seeing that many stink bugs still. Similarly, in a ThryvOn
demo plot we are sampling on a grower field in NE Alabama, we found 20% internal
injury while averaging less than 2 stink bugs per 100 sweeps. This helps to
make the point that we cannot be looking for stink bugs to make treatment
decisions. Pull some 10–12-day old (quarter sized) bolls and look for damage.
Peak bloom (weeks 3-6) is the most critical time to protect bolls and threshold
is just 10%.
What to Spray for the “Bugs”
We have reached the point in the season in this late planted
cotton, that we need to be thinking about both plant bugs and stink bugs when
making insecticide decisions. That doesn’t leave us many options, just
pyrethroids and organophosphates. Diamond will still have utility in some
situations, but this late in the year, that will come down to a field-by-field decision.
I have received several calls this week on “clean up” sprays of a pyrethroid
plus acephate. This is a common treatment that does a good job killing most everything
in the field and getting you through. There are likely some situations where
plant bugs need something like Transform for control, I would advise adding a
pyrethroid in the tank for stink bugs.
What about rates? At this point in the year, these plant
bugs have been hit by just about everything. For pyrethroids and Bidrin, I would
suggest running a 1:20 (6.4 oz) over a 1:25 (5.12 oz). The minimal savings on
insecticide cost doesn’t out weigh the drop in efficacy. For Diamond, it may
just depend on how much longer you need to go, but I am mostly recommending 6
oz still for most calls (if it is needed).
One other thought. As we reach the end of the year, try to get a final bug spray out before plants loaded up with bolls start to lean across the middles. In some cases, we may do more damage to bolls with the sprayer than stink bugs will do that late in the season.
Bollworms
We mentioned a few fields of Bollgard 2 requiring treatments
last week and a few more have been sprayed this week too. The diamides (Besiege,
Vantacor, Elevest) provide the best control, but are most effective on small
worms or when timed with a hatch out. Pyrethroids MAY still provide some
knockdown but scout behind them closely to make sure. Most of our fields are
3-gene (Bollgard 3, WideStrike 3 or TwinLink+) and we do not expect any issues
with controls in those fields.
Soybeans
Things are still pretty quiet on the soybean side are still
pretty quiet. We have heard of a few fields with low levels of loopers and
velvetbean caterpillars but not at treatable levels. We have also started
observing some stink bugs but not at damaging levels. Keep monitoring fields,
at some point things will pick up.
Peanuts
Again, things are still quiet. Defoliating caterpillars are
out there, but not at damaging levels. We have not heard of any spider mite
problems yet, so avoid disruptive insecticide applications to avoid creating
any issues.
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 (Scott Graham: 662-809-3368; 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 the Syngenta Pest Patrol Hotline.
