Okra leaf cotton effect on canopy microclimate and Helicoverpa zea (Boddie) egg hatch

Microclimates within cotton (Gossypium sp.) canopies can be affected by many factors including plant architecture. Changes in microclimate conditions can also impact insect populations. Standard upland cotton (G. hirsutum) typically has large leaves that provide shade, potentially lowering the temperature and increasing the relative humidity within the canopy. Such conditions could allow increased survival of pests, like the cotton bollworm (Helicoverpa zea). Field trials were conducted in New Mexico to evaluate how plant leaf shape could affect bollworm populations. To determine the potential influences of okra leaf on microclimate and insect survial, H. zea egg hatch was recorded in an open canopy okra-leaf variety (UA107), and a closed canopy (DP1845B3XF) variety with standard leaves. Clusters of 30-60 bollworm eggs were placed on leaf surfaces at mid and upper canopies in okra leaf and standard leaf cotton varieties. Egg clusters were retrieved after 48 hours and brought into the laboratory to record predation in the field and larval hatch at 48, 72, and 96 hours. Air temperature and relative humidity were recorded with HOBO dataloggers. There was significantly lower egg hatch in the okra leaf cotton with an average 31% hatch vs 54% in standard cotton. However, there were not significant differences in relative humidity or temperature which might explain the lower hatch rates. In 2021 this trial will be repeated as well as a trial to look at the possible impact of solar radiation that might explain lower hatch rates in okra leaf canopies.