Effect of Okra-Leaf Cotton on Canopy Microclimate and Helicovera Zea (Boddie) Survival

Microclimates within cotton (Gossypium sp.) agroecosystems can vary wildly depending on variety and the architecture of the plant which can impact insect populations. Traditional upland cotton (G. hirsutum) typically have large canopy cover providing shade, effectively lowering the temperature and increasing the relative humidity within the canopy. These conditions allow pests, like the Cotton bollworm (Helicoverpa zea), to thrive. To observe these effects, New Mexico State University collaborated with Cotton Incorporated to conduct trials at the Artesia Science Center. To elucidate potential influences of microclimate, they observed how Cotton bollworm egg hatch was influenced by two cotton varieties with distinct architecture: open canopy Okra leaf UA107, and closed canopy Bacillus thuringiensis (Bt) DP1845B3XF, an upland triple gene variety. Using a laboratory colony, clusters of approximately 30-60 bollworm eggs were embedded on fabric and stapled to leaf surfaces at mid-canopy where they remained for 48 hours. Egg clusters were collected and analyzed to record larval hatch at 48, 72, and 96 hours. Temperature and relative humidity were tracked with HOBO sensors which took readings every 30 minutes. Preliminary results show higher egg hatch in the closed canopy of the Bt cotton, suggesting that the cooler temperatures and higher relative humidity allow a higher proportion of eggs to successfully hatch. Utilizing such cotton varieties can play an important role in pest management especially in the arid environment of New Mexico. With this information, cotton farmers may integrate more open canopies within their cotton varieties to reduce the preferred environment of undesired pests.