The cotton jassid situation has continued to increase over
the last week in Alabama and across the lower Southeast. We have received reports
of infestations exceeding thresholds in 3 additional Alabama counties (Henry,
Baldwin and Cherokee) to go along with Coffee and Dale counties last week. The
biggest surprise was to hear of threshold populations in Cherokee county. Populations
appear to be spotty, which highlights the importance of scouting. Cotton
jassids are also going from undetectable to above threshold in as little as two
weeks in some cases. Part of this may be due to our recommended scouting
methods.
This week, we did a comparison of “flipping leaves” and
using a sweep-net as a detection tool. What we found was pretty obvious: using
the sweep-net is a much better way to detect low populations than just looking at
leaves. In fact, we were 3.5x more likely to find a cotton jassid in a sweep-net
than by flipping leaves. We also found ≈6x
as many adult jassids in 10 sweeps than we found on 10 leaves. I know that most
folks put their nets up long ago, but it may be time to get them back out. With
the current weather pattern, we cannot afford to miss these low populations of
jassids because the can blow up quick.
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| Early hopperburn symptoms in cotton in Henry, Co. AL. |
In conversations about this with people this week, a few
folks wondered what the sweep-net threshold would be. I do not think we will
ever be able to get to a sweep-net threshold. There would be too many to quantify
and nymphs are difficult to see in the net. However, the sweep-net is excellent
to rapidly detect these small numbers and let us know when to start flipping
leaves to see how close populations are to threshold. To scout with a
sweep-net, sing the net similarly to how you do in pre-square cotton for adult
plant bugs. You do not need to swing too hard and knock bolls and a lot of
leaves into the net. We have also found that cutting samples down to 10 sweeps
at a time makes it easier to count jassids and the keep from smashing them up
too much.
As a reminder,
threshold is one jassid (adult or nymph) per leaf. The presence of adults is critical
to understanding if nymphs are jassids or some other type of leafhopper as nymphs
are difficult to identify.
To date, most reports of cotton jassid exceeding thresholds
in Alabama have been in early planted cotton and cotton that is starting to crack
bolls. I suspect they will soon start moving into later planted cotton.
Hopefully if we catch them in older cotton, we can knock them back with a well-timed
insecticide application and reduce the populations moving into younger cotton.
For now, our recommendation is to scout and treat cotton at 1 jassid per leaf
until 2 weeks prior to defoliation.
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.
