Cotton IPM Update – Early Season Thrips

Cotton maturity ranges from germinating to 2 leaf. Cotton planted in the last week has been emerging in  5-6 days. This quick emergence is due to warm temperatures and adequate soil moisture.

Emergence to first square can take 27 to 38 days. We usually see the first squares 28-30 days after emergence. Thus, cotton planted March 27, emerged April 1-2 and should have the first squares by the first of May.

Thrips. Picture by David Kerns

The primary insect of concern is Thrips.

Thrips are slender, straw-colored insects about 1/15 inch long, with piercing-sucking mouthparts. Adults are winged and capable of drifting long distances in the wind. They attack leaves, leaf buds, and very small squares, causing a silvering of the lower leaf surface, deformed or blackened leaves, and loss of the plant terminal. Under some conditions, heavy infestations may reduce stands, stunt plants, and delay fruiting and maturity. Thrips damage is most evident during cool, wet periods when seedling cotton plants are growing slowly. Rain, blowing sand, wind, residual herbicide damage, and seedling diseases can worsen thrips damage.

Under favorable growing conditions, cotton can sometimes recover completely from early thrips damage. In areas in which seedling emergence typically occurs under warm conditions, thrips are usually of minor concern.

In most cotton fields, I am not very concerned about thrips injury right now. Most of the cotton fields have been planted with seed treated with insecticides that should provide insect control for 21-28 days after planting.

Thrips Injury. Phodo by Suhas Vyavhare

Another consideration is the variety planted. Fields planted with ThryvOn technology cotton varieties are also protected from thrips by the genetics in the seed. While ThryvOn cotton should provide some level of protection, don’t be complacent. We have not seen the ThryvOn in South Texas and need to evaluate it this season to make sure thrips respond in a similar way as in other parts of the cotton belt.

Continue to scout the crop for thrips. The economic threshold for thrips is generally 1 thrips per true leaf on the plant. With the growing conditions we are having, I would wait to see 2 thrips per true leaf to trigger an insecticide application if you are seeing leaf injury.

Find more information on thrips management HERE

Another insect of concern is the Cotton Aphid.

We often find cotton aphids in small pockets in fields, usually on plants in 2-3 feet of row with a lot of space between infested plants.

Cotton Seedling with Aphids. Photo by Stephen Biles

I have rarely seen these small colonies cause yield loss or delayed maturity. I would not be concerned with early season aphids unless they were in very high numbers (over 50-100 per leaf) on most of the plants across the field. If a field has this high of an aphid population, mark the spots and return to the field in 2-3 days to reassess the aphid population. These aphids will often appear and disappear rather quickly, and it will take a week or two for them to cause economic loss.

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