We have received several calls about thrips over the past 5-7 days. Right now, cotton planted in May is at the highest risk of thrips injury and cotton planted through about the 20th is at very high risk across most of the state. This has changed over the past week with all the rains we have received. One thing to consider is that a heavy rainstorm can alleviate some thrips pressure. However, they may not always do enough. On Saturday (May 18), we received a report from Cherokee county of multiple fields with anywhere from 2 – 6 thrips per plant on 1-2 leaf cotton (threshold is 1-2 with immatures present). Other reports are that cotton treated with AgLogic looks good and cotton with a seed treatment or imidacloprid in-furrow needs a spray.
Note: All reports are that ThryvOn cotton looks as expected and is not taking on injury justifying a foliar spray.
The question is, what to spray. There are a couple of
options for foliar treatments for thrips:
Acephate is an effective and relatively
inexpensive option, however it has the potential to flare secondary pests such
as spider mites and is the least rainfast of the available recommended options. (With the recent weather we have had, I am not concerned about flaring spider mites)
Bidrin is another option that is effective and
less likely to flare spider mites and is more rainfast than acephate, however
it is more likely to cause crop injury when tank-mixed with herbicides.
Intrepid Edge is another effective option.
Intrepid Edge is less likely to flare secondary pests but may need the addition
of a surfactant to help with efficacy.
Below is a chart with thrips counts and injury ratings from
an on-farm trial we did in 2020 in Madison County (AL).
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| On-farm thrips trial in 2020. Cotton was treated with Gaucho (insecticide seed treatment). Foliar application was made at the 1 true leaf stage. Ratings were made 7 days after application. An injury rating (yellow line) of "3" indicates unacceptable injury. |
We are still receiving reports of grasshoppers threatening
stands in central Alabama and the Wiregrass region. In some areas, we have a
good stand but rain is keeping us out of the field for a few days. In others,
the question has just been should we pull the trigger or not. In fields with
historic issues of stand loss from grasshoppers and high numbers in the field, treatment
should be considered. We don’t want to get into replant situations, especially
in areas where we lost a few days in the field and are trying to get caught up.
Acephate (2/3 lb) is needed to kill adults and in some fields nymphs are still
hatching and Dimilin can provide residual suppression. Cotton is most susceptible in the "crook" stage, but grasshoppers can still threaten stands once it has fully emerged.
If we can be of any help, please don’t hesitate to reach out
and let us know (Scott Graham: 662-809-3368; Ron Smith: 334-332-9501). To stay
up-to-date on the Alabama insect situation, subscribe to the Alabama Cotton
Shorts Newsletter,
Alabama Crops Report Newsletter,
and the Syngenta Pest Patrol Hotline.