Thrips are consistent pests of cotton in Georgia and the southeast as a whole. Thrips are the only insect pests of cotton that a preventive insecticide is recommended. For other insect pests of cotton, UGA recommends a reactive approach based on scouting and the use of thresholds.
Pests such as stink bugs, corn earworms, whiteflies, and remaining pests are less consistent and demand this reactive approach to maximize profitability. With most insect pests there are agronomic and management practices which influence the risk and severity of infestations.
Below are a few thoughts to consider as you make decisions for your at-plant thrips management program.
1. Use a preventive insecticide at planting. Positive yield responses are consistently observed in UGA research when an at-plant insecticide is used for thrips control.
2. At-plant insecticide options include in-furrow granule applications of aldicarb, in-furrow liquid applications of imidacloprid or acephate, and commercial seed treatments of imidacloprid, thiamethoxam, and acephate. Imidacloprid seed treatment is the most common at-plant insecticide used. In-furrow applications of aldicarb, imidacloprid, and acephate tend to provide greater residual control of thrips compared with the commercial seed treatments.
3. Historically thrips infestations and plant injury is greatest on early planted cotton (ie planted prior to May 10th). However, this high thrips risk window is a moving target from year to year. Temperature and rainfall during winter and early spring have a significant impact on thrips population development and the severity and timing of infestations moving to cotton. As we near planting you are encouraged to take advantage of the Thrips Infestation Predictor for Cotton. This web-based tool will predict thrips risk by planting date by geographic location and can be found at: http://climate.ncsu.edu/CottonTIP.
4. Thrips infestations are significantly lower in reduced tillage systems compared with conventional tillage. In general the more cover on the soil surface the greater the reduction in thrips.
5. Seedlings are most sensitive to yield loss during early developmental stages. 1-2 leaf cotton is at greater risk to yield loss from excessive thrips injury compared with 3-4 leaf cotton. Once cotton reaches the 4-leaf stage and is growing rapidly, thrips are rarely an economic pest.
6. A rapidly growing seedling can better tolerate thrips feeding. Conversely, seedlings which are growing slowly from cool temperatures or some other stress are more susceptible to thrips.
Scout for thrips and thrips injury early. Use thresholds and only make foliar applications when necessary. Optimal timing for supplemental insecticide applications (when needed) is the 1-leaf stage.