The cotton fleahopper adult is about 1/8 inch long, with piercing-sucking mouthparts and a flattened body (Fig. 16). Adults are active flyers; they readily flit within the cotton canopy when disturbed, which makes insect sampling a challenge. Their eggs are not visible because the adult inserts them into the cotton plant stem.
Adults are pale green to gray-green; nymphs are lighter-colored with reddish eyes (Figs. 17 and 18). Nymphs are very small and often confused with other plant bugs such as the verde plant bug and lygus bugs. Small black dots on the hind tibiae (fourth segment of the leg) distinguish late instar cotton fleahopper nymphs from other common plant bug nymphs.
In both the adult and nymphal stages, cotton fleahoppers suck sap from the tender portions of the cotton plant, including small squares. Pinhead size and smaller squares are the most susceptible to cotton fleahopper damage. Fleahopper feeding causes squares to die and turn dark brown. These “blasted” squares dry up and fall from the plant, leaving a characteristic scar on the fruiting site (Fig. 19).
When fleahoppers are abundant, heavy square loss can cause poor boll set and reduce yield. The first 3 weeks of squaring are the most sensitive to cotton fleahopper feeding, particularly in dryland cotton production.
The yield-cotton fleahopper relationship shifts with plant stage, water stress, weather, and cultivar sensitivity. Early squares are at high risk when large populations migrate into cotton from healthy stands of wild hosts that survived mild winter conditions. Yield reduction and development delays tend to be more pronounced in water-stressed cotton. Cotton fleahoppers can be more plentiful in vigorously growing cotton under good rainfall and irrigation, but their damage is less severe.
Scouting and Decision Making
There are two recommended scouting methods for cotton fleahop- pers: terminal inspection (Fig. 20) and beat bucket sampling (Fig. 3). Table 4 provides action thresholds for terminal inspection, and action thresholds for beat bucket sampling are in development.
For terminal inspection:
- As the first squares appear (approximately four- to six-leaf stage), examine the main stem terminal (about 3 to 4 inches of the plant top) of 25 plants in at least four locations across the fi Sample more sites in fields larger than 80 acres.
- Scout fields for cotton fleahoppers weekly. Cotton fleahoppers move into cotton in early summer as noncrop host plants mature and become Under wet spring conditions conducive to the rapid buildup of cotton fleahoppers in alternate hosts (such as cutleaf evening primrose, horsemint, silverleaf nightshade, and woolly croton), shorten the scouting intervals to every 3 to 4 days, especially as the alternate host plants begin maturing or undergo drought stress.
- When approaching a plant to sample, watch for adults that might fly from it. Cotton fleahoppers move quickly. Adults may fly away and immatures often hide within the plant canopy when disturbed.
Terminal inspection is applicable to all cotton production regions of Texas, and action thresholds are available (Table 4).
Beat bucket sampling is another sampling method for cotton fleahoppers. This sampling procedure is under development. Based on studies from South Texas, the beat bucket method is more effective in sampling for nymphs and more consistent for inexperienced users than the terminal inspection method. However, research to validate thresholds based on the bucket sampling method is currently incom- plete. Thus, at this time the bucket sampling method is recommended only as a means to detect cotton fleahopper infestations.
Chemical Control and Action Thresholds
Depending on the region, thresholds range from 10 to 30 cotton fleahoppers per 100 plants (Table 4). Preliminary studies indicate beat bucket thresholds will be higher. A range of 20 to 40 adults and nymphs per 100 plants is being tested in South Texas (Table 4). In some regions, combine insect density with square-set during the first 3 weeks of squaring.
After first bloom, fleahopper control is rarely justified. Insecticides applied during early bloom can result in outbreaks of aphids, boll- worms, and tobacco budworms because of the destruction of preda- ceous insects and spiders. Avoid using broad-spectrum insecticides after the second week of squaring.