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Title: AN ANALYSIS OF THE BEET ARMYWORM OUTBREAK ON COTTON IN THE LOWER RIO GRANDEVALLEY OF TEXAS DURING THE 1995 PRODUCTION SEASON

Author
item Summy, Kenneth
item Raulston, Jimmy
item Spurgeon, Dale
item VARGAS, J - CAMPO EXPTAL-RIO BRAVO

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/11/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: A series of insect outbreaks that occurred on cotton in the Lower Rio Grande Valley (LRGV) during the Texas production season contributed to an unprecedented crop failure and losses approaching $150 million. Surveys conducted in the LRGV of Texas during the height of these outbreaks revealed heavy plant damage, large numbers of beet armyworm and other cotton pests, and a general scarcity of beneficial insects that normally control these pests on cotton. In contrast, surveys conducted in adjacent Tamaulipas, Mexico revealed a low incidence of damage to cotton plants, relatively low densities of beet armyworm and other pests, and relatively high densities of green lacewings and other beneficial insects. This contrast indicated that populations of beneficial predators and parasites had become seriously disrupted in the LRGV of Texas. One plausible explanation is the relatively high volume of pesticides that were employed in the latter area during the 1995 production season. These results indicate the importance of green lacewings and other predators, and the need to use pesticides judiciously in order to avoid serious outbreaks of beet armyworm and other secondary pests.

Technical Abstract: 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 (Hubner), and other lepidopterous and homopterous pests, and an apparant 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. One plausible explanation for this disruption is heavy use of pesticides. 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.