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Thrips Management – Roberts


Thrips Management (Phillip Roberts): Thrips are consistent pests of cotton, infesting nearly all cotton
acres planted in Georgia each year. Thrips are the only insect pest of cotton that a preventive insecticide is
recommended. We consistently observe a positive yield response to at-plant insecticides used for thrips
control. A reactive approach based on scouting and use of thresholds is recommended for less consistent
insect pests such as stink bugs, corn earworms, whiteflies and others 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. Thrips will infest near 100 percent of cotton planted in
Georgia. We consistently observe positive yield responses in UGA research and on the farm when
an at-plant insecticide is used for thrips control. It is not feasible to control thrips with foliar
sprays alone; multiple foliar sprays applied in a very timely manner would be required.
2. At-plant insecticide options include infurrow granule applications of aldicarb, infurrow liquid
applications of imidacloprid or acephate, and commercial seed treatments of imidacloprid,
thiamethoxam, and acephate. Infurrow applications of aldicarb, imidacloprid, and acephate tend to
provide greater control and longer residual control compared to seed treatments.
3. Thrips infestations are generally higher on early planted cotton compared with later planted cotton.
High risk planting dates for thrips injury is a moving target from year to year. The Thrips
Infestation Predictor for Cotton (http://climate.ncsu.edu/CottonTIP) is a web-based tool which
predicts thrips risk by location and planting date. This tool was developed by researchers at North
Carolina State University and has been verified using thrips data from Georgia. The website has
information about the tool and also includes a link to a presentation describing the tool and how it
can be used in the “About” tab. If the risk is high for thrips on a given planting date, consider
using a more active at-plant insecticide or be prepared to scout and potentially make a timely foliar
spray if a seed treatment is used.
4. Thrips infestations are significantly lower in reduced tillage production systems compared with
conventional tillage. In general, the more cover or residue on the soil surface the greater the
reduction in thrips.
5. Cotton seedlings are most sensitive to yield loss from thrips feeding during early stages of
development. Excessive thrips feeding and plant injury on 1-2 leaf cotton has a greater yield
penalty than cotton infested at the 3-4 leaf stage. Once cotton reaches the 4-leaf stage and is
growing rapidly, thrips are rarely an economic pest.
6. Slow growing seedlings are more susceptible to thrips than rapidly growing seedlings. If cotton is
slow growing due to herbicide injury, cool temperatures, or other stresses, be sure to scout for
thrips and thrips injury. Thrips feed in the terminal bud on unfurled leaves so more feeding occurs
on each unfurled leaf if the plant is growing slowly.
7. Scout for thrips and injury early. The threshold for thrips is 2-3 thrips per plant with immatures
present. The presence of immature thrips suggests the at-plant insecticide is not providing control
(i.e. thrips eggs were laid on the plant, eggs hatched, and immature thrips are surviving). Immature
thrips are crème colored and lack wings whereas adults will typically be brown with wings.