Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/1/2003
Publication Date: 4/1/2004
Citation: Greenberg, S.M., Showler, A., Sappington, T.W., Bradford, J.M. 2004. Effects of burial and soil condition on postharvest mortality of boll weevils (Coleoptera: Curculionidae) in fallen cotton fruit. Journal of Economic Entomology. 97(2):409-413. Interpretive Summary: Cotton production in the United States continues to be limited by boll weevil populations which caused an estimated crop loss of 838,900 bales in 2002 despite the use of conventional insecticides. Alternatives to conventional insecticides include cultural control techniques such as tillage operations that modify the soil habitat of boll weevils during part of their life cycle. We found that the major factor responsible for the mortality of boll weevils in fallen cotton fruit in post-harvest conservation tillage fields in the Lower Rio Grande Valley was high soil surface temperatures. However, boll weevil mortality in post-harvest conventional tillage fields was reduced because the larvae in buried infested cotton fruit were protected from lethally hot temperatures by the 25-cm layer of soil. Burial of infested fruit resulted in significantly greater weevil mortality in wet sand or clay than in dry or clumpy soil conditions. Our study demonstrated the feasibility of cultural management of overwintered boll weevil control. Results from this research show additional benefits of conservation tillage, other than wind erosion control and water conservation.
Technical Abstract: Effects of soil condition and burial on boll weevil, Anthonomus grandis grandis Boheman, mortality in fallen cotton, Gossypium hirsutum L., squares and bolls (fruit) were assessed in this study. During hot weather immediately following summer harvest operations in the Lower Rio Grande Valley of Texas, burial of infested fruit in conventionally tilled field plots permitted greater (P </= 0.05) survival of weevils than in no-till plots. Because the high mortality observed in infested fruit on the soil surface resulted from heat, burial of infested fruit appeared to have protected developing boll weevils from lethal thermal temperatures during the late growing season. The lethal effect of heat was underscored when boll weevils developing in fruit on the soil surface in three locations of Texas died in significantly greater (P </= 0.05) numbers in hotter months than in the next cooler month. A laboratory assay showed that burial of infested fruit resulted in significantly greater (P </= 0.05) weevil mortality in wet sand or clay than in dry or clumpy soil conditions. The laboratory assay supports the results of a field experiment where boll weevils in buried fruit during winter, late November to mid-February, in the Lower Rio Grande Valley emerged to the soil surface in significantly lower (P </= 0.05) numbers than control fruit on the soil surface. This result is attributed to thorough wetting of the soils by winter rainfall. Burial of infested cotton fruit by tillage might be a major mortality factor for overwintering boll weevils in fallow cotton fields.