As I have looked at cotton this spring one of the most dramatic observations I have made is the impact of tillage on thrips populations. Thrips injury is significantly less in reduced-tillage systems compared with conventionally-tilled cotton, especially when there is a large amount of cover crop residue on the soil surface.

A common question I have received is whether the seed treatments are working. The answer is absolutely yes! 

The control which they offered is very evident in small plot trials where we commonly compare treatments to an untreated control. Granted, foliar sprays have been needed, but the seed treatments did help. It would be near impossible to manage thrips with foliar sprays alone on a year like we have had. 

Years ago it was not uncommon for an in-furrow granule tube to stop up periodically and we were reminded at how bad thrips could be without an at-plant insecticide treatment.

In terms of management, take the time to scout and make foliar applications if thresholds are exceeded. Foliar sprays should be applied if thrips exceed 2-3 per plant and immatures are present. 

Immature thrips are crème colored and wingless, where as adults will be brown or blackish and have wings.

Seedlings remain susceptible to thrips injury until they reach the 4-leaf stage and are growing vigorously.

Excessive injury during early seedling stages (1-2 leaf) has a greater impact on yield potential than injury on 3-4 leaf cotton. So if you have a problem on 1-2 leaf cotton, address it in a timely manner. 

We would expect thrips numbers to begin to decline soon, but in the interim, scout, scout, scout.

When foliar applications are made on cotton which has severe damage, it is likely the next leaf to unfurl will also have damage (remember that thrips are feeding on unfurled leaves in the terminal bud). The second leaf to unfurl should look better.

Retreatment of a field should be based on thrips counts and not the appearance of the next leaf to unfurl. There is no question that maturity has been delayed on some early planted fields, but cotton is resilient and will recover in most situations. 

In severely damaged fields some terminals may abort and the plant may “sucker out” and appear as “crazy cotton” with multiple terminals. 

I am amazed each year at how bad plots with no at-plant insecticide for thrips can look during the seedling stage and that they can recover and still make respectable yields. 

 

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