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Influence of Coton Varieties on Arthropod Fauna

P. B. Goodell, C. M. Garcia, K. D. Keillor, C. Haas, L. D. Godfrey and D. Munk


 
ABSTRACT

Arthropods were sampled weekly in 1999 and 2000 from eleven replicated variety trials in the San Joaquin Valley (SJV). Ten sites contained both upland and Acala varieties while one plot contained Upland, Acala and Pima varieties. No significant differences were found in total arthropod population between varieties at most locations. Exceptions included three sites in which total lygus were greater on C-166, gossypol-free experimental Acala cotton and a single site where aphid were also greater on C-166. Natural enemies differed between varieties in more locations but their presence did not correspond to varieties and sites in which pests were significantly greater. Transgenic Bt and non-Bt cotton were compared for their influence on natural enemy insect populations during 1999 and 2000. Significantly greater total population of big-eye bug was found in 1999 on Bt cotton. In 2000, one trial had significantly greater or less green lacewing on Bt and non-Bt cotton.

Only nine locations contained both Acala, Upland and Pima. These were chosen to ensure uniform arthropod presence. Four varieties each of Acala and Upland trials and two varieties of Pima (including Upland and Acala variety) were sampled in 1999 (Table 1). In 2000, only two locations had both Acala and Upland trials (Table 2).

Each location was sampled weekly for arthropods. The guard rows were sampled to avoid damage to harvest rows. Insects were collected with a standard 38-in sweep net using 50 sweeps across the top of the plants. The insects were transferred to a paper bag and placed in a freezer. Insects were identified and enumerated within five days of collections. Adults and nymphs of common insects were classified to adult or immature stage except for Western Tarnished Plant Bug (WTPB), Lygus hesperus, where adults were sexed and immatures identified to instar class and green lacewing where only adults were counted. Ten leaves located five nodes from the top of the plant were collected each week. The leaves were washed in 0.5 % bleach solution to remove mites and aphids. These were collected and counted under a microscope.

Data were entered weekly but for this paper, only the seasonal totals are presented. ANOVA and mean separation (Fishers Protected LSD) were used to analyzed the data set. Data for WTPB, cotton, aphid, spider mites, minute pirate bug, big-eye bug and green lacewing.





Reprinted from Proceedings of the 2001 Beltwide Cotton Conferences pp. 1019 - 1021
©National Cotton Council, Memphis TN

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Document last modified XXXXXX, XXX XX 2001