Cotton. The cotton insect situation has been all over the board this year. Calls and reports have been that insects are sporadic. Heavy in some areas while others will likely go with no foliar insecticides for insects for the first time in years. We have reached (or rapidly approaching) insect cutout on early planted cotton. Below are a few guidelines for when to terminate applications:
1.
Plant Bugs: Node above white flower 2 (NAWF2).
That is, when there is an average of 2 node above the highly first position
white flower, cotton is generally safe from plant bugs.
2.
Stink Bugs: Bolls that are expected to make it
in the basket should be protected until they are ~25 days old. Keep in mind
that as we get later into bloom, the amount of internal boll damage (IBD) needed
to justify an application increases. Weeks 3-6=10% IBD; Week 7=30% IBD; week
8=50% IBD.
3.
Spider Mites: This can be a tricky call (as can
be when to treat in general). A threshold for spider mites of 30-50% infested
plants showing injury is the best we have. Some considerations for terminating
treatments include age of the cotton and how bad the infestation is. Bolls that
are expected to be harvested should be protected from mites until they are
about 20 days old. How bad is too bad? This is hard to say, but you cannot walk
away from a disaster. If mites are turning leaves red and defoliation can
happen, action is needed.
Cotton Jassid: The cotton jassid (or two-spot cotton
leafhopper) is an invasive insect originally from India. This insect was found
in Puerto Rico in 2023 and in Florida in 2024. This insect has been widely
detected in many counties in Georgia and has also been found at damaging levels
in Florida and South Carolina. To date, while we have reports of cotton jassid
in Alabama, we have not received reports or observed damaging levels in
Alabama.
Cotton jassids are small (1/10 inch in length) leafhoppers
that damage plants with sucking mouthparts and feed on the underside of leaves.
Our initial observations indicate that they usually infest field edges (like
SLWF). While infestions are low in a lot of cases, they have the potential to
blow up quickly. This insect can turn over a generation in as little as 10
days.
To scout, turn an individual expanded leaf from one of the
top 5 nodes and count cotton jassids on the underside of the leaf. We cannot identify species of nymphs but
adults are easily recognized by two black spots on the wings. Plant injury
includes yellowing of leaves on the outer edges or hopper burn or leaf puckering
(see pics below). If you detect jassids in the field please contact your local
Extension Agent for the most current information on thresholds and insecticide
selection. This is an evolving situation and management strategies are subject
to change. (Note: to date, cotton jassid has only been observed in commercial
fields of the SE corner of Alabama, Henry and Houston counties.)
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| Adult and immature Cotton Jassids. |
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| Cotton Jassid symptomology. |
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| Cotton Jassid symptomology. |
Soybean. The soybean insect situation has started to
build in the the past week. We are receiving more reports of defoliating
caterpillars and stink bugs across Alabama. In most cases, soybean loopers have
not been a large portion of the defoliator mix, but there are enough to take
notice.
Our threshold for defoliating caterpillars (loopers,
cloverworms, velvetbean caterpillars) is to avoid 20% defoliation during
reproductive stages. For soybean loopers (SBL), treatment is recommended if 18
loopers (> 0.5 inch) is found per 25 sweeps. Velvetbean caterpillar (VBC)
and green cloverworm (GCW) threshold is 36 per 25 sweeps. Most labeled
insecticides do a good job controlling VBC and GCW, while newer materials
(Vantacor, Besiege, Intrepid Edge, etc.) are needed to control SBL.
In addition to our traditional stink bugs species, we have
also heard of some redbanded stink bugs in fields in central Alabama. In most
cases, they are just part of the complex and not the dominate species. However,
some fields have had one or more applications for RBSB. Threshold for stink
bugs is 6 per 25 sweeps* until R6. At R6 threshold is doubled to 8 per 25
sweeps for the next 7-10 days. While Pyrethroids provide good control at the
high labeled rate, tank-mixtures of Pyrethroids and Acephate (or neonics) are
needed to control RBSB. (*note:
threshold for RBSB is 4 per 25 sweeps).
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.
