Thrips Management by Dr. Phillip Roberts.

Thrips infest seedlings the day of emergence and remain a threat to yield until cotton reaches the 4-leaf stage and is growing rapidly. Thrips infest all cotton planted in Georgia every year. On cotyledon cotton, thrips feed on the underside of leaves which will cause a “silvery” sheen on the underside of the cotyledon. More importantly, thrips deposit many eggs in the cotyledons. These eggs will hatch in 5-7 days depending on temperature and immature thrips will move to the terminal and feed on unfurled leaves. This is one of the biological reasons a 1-leaf foliar spray for thrips perform so well. As true leaves unfurl and expand, damaged leaves will be crinkled and distorted. Excessive injury causes stunting and reduced yield potential and in severe cases plant mortality. Since thrips are so predictable, preventive treatment is recommended at planting.Preventive insecticide treatments include AgLogic applied as an in-furrow granule, imidacloprid or acephate applied as an in-furrow liquid, or commercial seed treatments (primarily imidacloprid). Infurrow applications typically provide greater and longer residual control of thrips compared with seed treatments. ThryvOn varieties also provide excellent thrips protection.Supplemental foliar sprays may be needed for thrips if infestations are high or environmental conditions are not conducive for uptake of the at plant insecticide. The threshold for thrips on nonThryvOn cotton is 2-3 thrips per plant with immatures present. The presence of immature thrips suggests the preventive insecticide is not providing control. A rapidly growing seedling can better tolerate thrips damage. It is also important to note that seedlings are most susceptible during early growth stages. For example, seedlings in the 1-2 leaf stage are at greater risk to yield loss than seedlings in the 3-4 leaf stage. On ThryvOn cottons, do not use thrips counts to determine the need for a supplemental foliar spray. We have never observed a need for supplemental foliar thrips insecticide on ThryvOn cotton, even when threshold counts of thrips are exceeding the recommended threshold for non-ThryvOn cottons. The threshold for thrips on ThryvOn cotton is to treat if excessive plant injury is present and immature thrips are present.