Analyses of boll weevils captured near hay bales

Authors: Jones, Gretchen; TROXCLAIR, NOEL - Texas A&M Agrilife

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/20/2010
Publication Date: 4/19/2010
Citation: Jones, G.D., Troxclair, N. 2010. Analyses of boll weevils captured near hay bales. National Cotton Council Beltwide Cotton Conference. p. 1004-1010.

Interpretive Summary: The boll weevil, Anthonomus grandis Boheman, remains one of the most devastating insect pests of cotton, Gossypium hirsutum L., in the southern United States. Re-infestations of weevils in cotton fields in Louisiana have been correlated with the transport of large hay bales. It is unknown if this correlation is due to the structure of the hay bale or the use of the hay bale as a refuge for the weevils. To assess the possibility that weevils were using hay bales as a refuge, three criteria were assumed: numerous grass pollen grains, numerous fungal spores, and the presence of grass cells found on weevils. Weevils were collected from pheromone traps that were placed downwind from hay bales in the Uvalde District of the Texas Boll Weevil Eradication Program. No single pollen type was found in all samples. Grass pollen was found more often than any other taxon. Following the grasses in abundance were the “low spine” Asteraceae pollen types (14 grains). Cotton (Gossypium hirsutum L) pollen grains were found in three weevils. The diversity of pollen found in these samples represents the vegetation in the Uvalde District. Seven fungal spore types and 44 fungal spores were found in the samples, all of which are not restricted to hay. No grass cells were seen in the samples. The observed pollen and fungi types and the lack of grass cells indicate that these weevils did not exist for long periods within or near the hay bales. Additional research is needed to examine more weevils and nearby hay bales.

Technical Abstract: Boll weevils re-infesting cotton fields in Louisiana were often correlated with the movement of large hay bales in the area. Boll weevils were collected in pheromone traps that were placed downwind from hay bales that were in varying stages of decay in numbers ranging from 10 to greater than 30. Boll weevils were collected in the Uvalde District of the Boll Weevil Eradication Foundation in Texas. To indicate possible refuge of the weevils near or in hay bales, the weevils were examined for pollen grains, fungal spores and phytoliths (plant cells). Over all 103 pollen grains from 38 different taxa were found in the samples. No one pollen type was found in all samples. More grass pollen grains (25 including 2 corn pollen grains) were found than any other taxon. Following the grasses were the “low spine” Asteraceae type with 14 grains, and then the Cheno-Ams and Celtis sp. (hackberry), both with 7 grains each. Cotton (Gossypium) pollen grains were found in three weevils. The diversity of pollen taxa is representative of the vegetation in the Uvalde District, Texas, which is in the South Texas Plains Vegetation Zone. Seven fungal spore types and 44 fungal spores were found in the samples and one type of fungal hypha. No single spore type occurred in all the samples. One Puccinia (wheat rust) and a Stemphylium spore were found in the samples. No grass phytoliths were seen in the unacetolyzed or acetolyzed samples. The pollen taxa present, the generalistic habit of the fungi and the lack of grass phytoliths, indicate that these weevils did not exist for long periods within or near the hay bales. However, additional research and a greater number of weevil samples are needed to determine if these techniques can be used to distinguish weevils associated with hay bales.