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An Analysis of the Beet Armyworm Outbreak on Cotton in the Lower Rio Grande Valley of Texas During the 1995 Production Season

K.R. Summy, J.R. Raulston, D. Spurgeon, J. Vargas


A survey was performed in the cotton-production region of the Texas and Tamaulipas Lower Rio Grande Valley (LRGV) following a series of destructive insect outbreaks that extensively damaged the Texas LRGV cotton during 1995. Surveys in the Texas LRGV cotton acreage revealed heavy damage to plants, relatively high densities of beet armyworm, Spodoptera exigua (Hübner), and other lepidopterous and homopterous pests, and an apparent general scarcity of an index predator, the green lacewing (Chrysoperla spp). Similar surveys in the Tamaulipas LRGV revealed a low incidence of plant damage, low densities of lepidopterous and homopterous pests, and relatively high densities of green lacewings. These trends indicated a disruption of green lacewing populations and by extrapolation--probable disruption of other predator and parasitoid populations in the Texas LRGV cotton. A prominent difference between the study areas in the initiation of pesticide treatments to the 1995 cotton crop was the area-wide application of ULV malathion and pesticide applications for aphid control in the Texas LRGV. We hypothesize that the early-season pesticide use pattern is one of the most plausible explanations for the observed pest outbreaks in the Texas LRGV. Severe insect damage to Texas LRGV cotton resulted in a compensatory square production that facilitated an abnormally high incidence of boll weevil reproduction during July and August.

Reprinted from Proceedings of the 1996 Beltwide Cotton Conferences pp. 837 - 842
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998