Effect of boll weevil on the yield and fiber quality on the south plains of Texas

The cotton boll weevil Anthonomus grandis (Boheman) has caused significant economic losses to Texas High Plains cotton Gossypium hirsutum (L.) since population densities drastically increased over the last four years. During 1997 and 1998, a replicated field study was conducted at Lubbock, TX to: 1) determine if 28 cotton varieties adapted to Texas High Plains growing conditions, could tolerate high boll weevils densities in terms of yield and fiber quality; 2) determine the effect of high boll weevil infestations on fiber quality and 3) to improve techniques for the field evaluation of genetically altered cotton for boll weevil damage assessment. This study showed that failure to control boll weevil under high densities caused severe economic losses in lint yield, but did not reduce fiber quality components as measured by High Volume Indexing (HVI) analysis. None of the 17 commercial varieties or 11 mutant lines evaluated under heavy boll weevil infestation were found to have useful levels of tolerance based on yield and fiber quality. The split-plot design of multiple insecticide applications versus no-applications for the same varieties provided an economic screen for boll weevil damage assessment. Accounting for whole-plant insect densities, boll shed versus boll injury and increasing the number of replications should improve statistical outcome in the evaluation procedure.