Predation of Sentinel Bollworm Eggs in Glanded and Glandless Cotton in New Mexico

Cotton glands produce gossypol, a natural defense against insect pests. Glandless cotton varieties are available, but losses from pests have prevented commercial development.  Some areas of New Mexico have lower insect pressure, with high predation and desiccation suppressing pest populations.  With appropriate management and monitoring of insect pests, growers could potentially produce glandless varieties as a niche crop with greatly added seed value. Field to lab trials were conducted on New Mexico State University farms to evaluate predation rates in glandless vs. glanded cotton in an effort to develop pest management strategies for glandless cotton protection.  Sentinel cotton bollworm eggs were attached to glanded and glandless cotton plants on multiple dates in 2011-2013 to evaluate potential differences in predation. Insects were also sampled from plots weekly using sweep nets.

Total predation was 56% and 53% in glanded and glandless cotton respectively in 2011, but 71% and 79% in 2012.  Damage to eggs was classified as being from predators with chewing or sucking mouthparts. Predators were generally collected in similar numbers in glanded and glandless cotton plots both years.  However, there were significantly more spiders and ladybugs in glanded cotton plots early season in 2011 and significantly more spiders season long in glanded cotton plots in 2012.  Predation by predators with chewing mouthparts was also significantly higher in 2012 with an average 78% vs 47% predation of sentinel eggs in glanded vs glandless plots. Overall similarity in predation rates in glanded and glandless cotton suggests that predation will be an important source of control of insect pests in glandless cotton.