Contribution of Crops, Weeds, and Parasites to the Abundance of Silverleaf Whitefly in San Joaquin Valley Cotton

L. D. Godfrey, P. B. Goodell, W. J. Bentley, C. G. Summers, T. Prather, and R. Coviello


Field populations of the silverleaf whitefly (SWF) were first found in the San Joaquin Valley (SJV) of California in July 1992. Several cotton fields in the southern end of the SJV were infested with low-moderate levels of SWF. The diversity of crops grown in this area may provide many excellent hosts for this severe pest. A study was started in 1993 to evaluate the suitability of SJV crop and weed plants as hosts for SWF. Populations of SWF on potential host plants were quantified within 12 areas, 36 sq. mi. each, on a biweekly basis. Sampling commenced on 1 May and has continued to 1 January. SWF were first identified on 2 June from a honeydew melon field in Kern County. Infestations in cotton generally did not start until early to mid August. Many cotton fields were infested at low levels, but serious infestations were not widespread in 1993. Lint stickiness from SWF was not a major problem. Upon cotton defoliation, SWF were subsequently found on alfalfa, fall potatoes, carrots, and leafy vegetables, as well as on weeds, such as smooth pigweed and tree tobacco. In summary, about 30 different crop plants, over 40 different weed species, and about 15 different ornamentals were SWF hosts. Going into the overwintering period, SWF are present on several weed species (e.g., malva, Malva parviflora), crop plants (e.g., cole crops, alfalfa, and citrus), and ornamental/residential plants. The survival of SWF on these plants during the cool, damp winter will be a critical factor in determining the damage potential of this pest on cotton in 1994.

Reprinted from Proceedings of the 1994 Beltwide Cotton Conferences pp. 873 - 874
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998