Effects of microclimate on cotton bollworm (Helicoverpa zea) egg hatch in upland cotton

Microclimates within cotton (Gossypium sp.) agroecosystems can vary depending on variety and the architecture of the plant which can impact insect populations. Traditional upland cotton (G. hirsutum) typically have large leaves that provide 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 in two cotton varieties with distinct architecture: open canopy okra leaf UA107, and closed canopy Bacillus thuringiensis (Bt) DP1845B3XF, an upland variety with normal leaves. 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 and predation 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 normal leaf cotton, suggesting that the warmer temperatures 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 open canopy varieties within their cotton systems to reduce the preferred environment of undesired pests.