A PROSPECTUS - IMPACT OF HELICOVERPA-ZEA LEPIDOPTERA, NOCTUIDAE (BODDIE) PRODUCTION FROM CORN IN THE LOWER RIO-GRANDE VALLEY ON REGIONAL CROPPING SYSTEMS

Corn production in the Lower Rio Grande Valley of Texas and Mexico dur ing June, and on the Texas High Plains in late summer, annually provid es areas for the production of billions of corn earworm/cotton bollwor m, Helicoverpa tea (Boddie), adults. Strong evidence indicates that ad ult populations emerging in June in the Lower Rio Grande Valley typica lly undertake long-distance flights via weather transport systems to m ore northern latitudes such as the Texas High Plains. However, pheromo ne trap capture data taken from Louisiana, New Mexico, Oklahoma, and T exas did not consistently indicate a relationship between the density of corn earworms produced in the Lower Rio Grande Valley and subsequen t downwind corn earworm trap captures and percentage yield losses in c otton during 1984-1989. In 1984, when corn earworm production in the L ower Rio Grande Valley was the second lowest of the study, the highest trap captures of corn earworm were observed at all recipient location s except Dallas. However, when corn earworm production levels were com parable in the Lower Rio Grande Valley (1986, 1988, and 1989), capture s of corn earworm in pheromone traps during June and July at Lubbock a nd College Station, Texas, and Bossier city, Louisiana, tended to be s imilar at their respective locations. The lowest production of corn ea rworm in the Rio Grande Valley corn crop (1987) resulted in the lowest trap captures at all study locations. At present, it is exceedingly d ifficult to assess the specific impact of migrating corn earworms on c rops grown in areas such as the Texas High Plains during June and July . However, the estimated annual cost of insecticides to control corn e arworm in pre-bloom cotton on the Texas High Plains, in years of moder ate populations, is approximately $2 million dollars. Later generation s of corn earworm that develop on the approximately 110,000 ha of corn on the High Plains apparently account for the annual, chronic infesta tions in cotton during August and September. Thus, the association bet ween corn earworm immigration in June and July and the resulting damag ing populations that occur in corn and cotton during late season is hi ghly suspect but requires additional research for confirmation. The au thors address the various facets of the disciplines involved in invest igating the processes, implications of corn earworm migration, and exp ress the need to expand and continue long-term, area-wide, cooperative research on potential source areas for corn earworm populations.