What is in this article?:
- Is your cotton field at high risk or low risk for thrips?
- Some research to back it all up
- Georgia cotton planted in April or early May in a conventional tillage system is “High Risk” for thrips. Cotton planted after mid-May and/or in a reduced tillage system is “Low Risk” for thrips.
Cotton planted in April or early May in a conventional tillage system would be considered “High Risk” for thrips. Whereas cotton planted after mid-May and/or in a reduced tillage system would be considered “Low Risk” for thrips.
Thrips infestations are typically higher on cotton planted during April and early May compared with late May and June plantings. Thrips infestations are also significantly greater in conventional tillage systems compared with reduced tillage systems. A risk index of thrips infestations may be predicted for cotton planted based on these two cultural practices, planting date and tillage practice.
Preventive insecticide treatments at planting are used by most growers for early season thrips control. The most common preventive treatments include the systemic insecticides imidacloprid or thiamethoxam applied as a commercial seed treatment. Additional options for early season thrips control include acephate or imidacloprid applied as an in-furrow spray.
Both imidacloprid and thiamethoxam are neonicotinoid insecticides and performance in Georgia has historically been similar when used as a seed treatment for thrips control; thus we will refer to these commonly used treatments collectively as neonicotinoid seed treatments (NST). NSTs are active on thrips for about 21 days after planting (DAP); however, supplemental foliar sprays are needed in some environments (high thrips populations and/or extended infestations).
Commercial seed treatments including imidacloprid or thiamethoxam provide similar levels of thrips control and are active on thrips for about three weeks after planting. NSTs provide a consistent yield response in both low and high thrips risk environments. However, research and observation have shown that a supplemental foliar insecticide spray is often needed in addition to a NST when thrips infestations are high, i.e. high thrips risk environment.
All cotton should be scouted on a regular basis for thrips and other insect pests, but we should expect higher thrips populations on cotton planted prior to May 10 in a conventionally tilled system compared with cotton planted after May 10 and/or in a reduced tillage system. Unless frequent and thorough scouting reveals thrips populations are below the threshold of 2-3 thrips per plant with immatures present, a foliar thrips systemic insecticide should be applied at the 1-leaf stage in conventional tilled fields planted prior to May 10 when a NST is used.
Thrips are consistent and predictable insect pests of seedling cotton in Georgia. Thrips infest cotton at emergence and initially feed on the lower surface of cotyledons prior to feeding in the terminal bud of developing seedlings. Excessive thrips feeding results in crinkled malformed true leaves, stunted plants, delayed maturity, reduced yield potential, and in severe cases loss of apical dominance and stand loss. Cotton seedlings are most susceptible to thrips during early stages of development (cotyledon thru 2- leaf). Once seedlings reach the 4-leaf stage and are growing rapidly thrips are rarely an economic concern.