Potential of yellow sticky traps for lady beetle survey in cotton.

A 2-yr study was conducted to investigate the potential of using yellow sticky traps to survey lady beetles in cotton and to quantify seasonal activity patterns. The performance of sticky traps was compared with that of a 2-cycle vacuum sampler. The most common lady beetle species captured by sticky traps and vacuum sampler in cotton were Hippodamia convergens Guerin-Meneville and Scymnus loewii Mulsant. Sticky traps captured significantly more of both species of lady beetles, had greater capture efficiency, and more effectively detected lady beetles compared with the vacuum sampler. These data indicate that the sticky trap can be a valuable tool in monitoring lady beetle populations in cotton. In the second part of this study, a year-round survey of lady beetle populations in the periphery of a cotton farm using sticky traps showed that lady beetles remained active throughout the year in the Texas Rolling Plains, but the activity was influenced by winter severity. Over a 2-yr period, H. convergens, S. loewii, Coccinella septempunctata (L.), and Olla v-nigrum (Mulsant) comprised 89.6, 8.2, 1.9, and 0.3% of the specimens, respectively. Sticky trap captures were affected by year, trap height, and cropping season. Traps placed at 0.75 m above ground captured significantly more (80%) lady beetles than traps placed at 1.50 m (20%) above ground; traps at 0.75 m above ground also detected the rarer species while the traps at 1.50 m above ground detected only the abundant species. Trap captures were higher during the noncotton season (November to April) compared with the cotton season (May to October). A significant positive correlation between cotton aphid abundance during the growing season and H. convergens abundance during the following noncotton season was also detected, indicating a significant movement of H. convergens from cotton to the periphery of the farm to seek refuge after cotton termination.

Relationship between Aphis gossypii (Homoptera: Aphididae) and sticky lint in cotton.

The study was conducted in the northern Texas Rolling Plains in 1999 to define the relationship between number of cotton aphids, Aphis gossypii Glover, and resulting contamination of cotton lint by honeydew. Whole-plot treatments were three furrow irrigation management treatments: cotton grown without supplemental irrigation (dryland), irrigated cotton with last irrigation in mid August, and irrigated cotton with last irrigation in late August. Subplots within each irrigation treatment included an untreated check, a plot treated with lambda-cyhalothrin to stimulate aphid population increase, a plot treated with lambda-cyhalothrin followed by pymetrozine after aphids began to increase, and a plot treated with lambda-cyhalothrin followed by thiamethoxam after aphids began to increase. Cotton aphids were counted on leaves picked from the top and bottom half of the plant. Cotton lint was analyzed for contamination by glucose, fructose, sucrose, and melezitose secreted by cotton aphids, and percentage leaf moisture and nitrogen and leaf sucrose concentrations were determined. The manual sticky cotton thermodetector was used to determine degree of lint stickinesss. There was a significant relationship between thermodetector counts and melezitose contamination on lint, and a melezitose concentration of 90.9 microg/g of lint was associated with a thermodetector count of 10, the threshold for sticky lint problems in textile mills. An equation was developed to estimate melezitose concentration on lint as a function of average numbers of aphids per leaf and the interaction between percentage leaf moisture and nitrogen. The number of aphids per leaf associated with a melezitose concentration of 90.9 microg/g of lint ranged from 11.1 to 50.1, depending on percentage leaf moisture and nitrogen. The threshold for sticky lint problems occurred when aphid numbers ranged between 11.1 and 50.1 per leaf after bolls open.