Predation of sentinel bollworm eggs in glanded and glandless cotton

Glandless cotton produces seed that is edible and thus represents a new market but development has been limited by losses from insect pests. 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 2011-2015 to evaluate potential differences in predation. Insects were also sampled from plots weekly using sweep nets.

Total predation was similar in both glanded and glandless plots in all years averaging 64 and 66% predation across all dates and years.  Predators were generally collected in similar numbers in glanded and glandless plots every year. However, there were surprisingly significantly more ladybugs and spiders in glanded cotton plots. Predation by predators with chewing mouthparts was also often significantly higher in glanded plots with, for example, 78 vs 47% predation of sentinel eggs in glanded vs glandless plots. At the same time twice as many spiders were collected in glanded plots suggesting that they are more important predators in glanded cotton.  Although spiders were less prevalent in glandless cotton, a number of other predators present brought the total predation levels up to levels similar to that in glanded cotton.  Predation should be at least equal to glanded cotton and an important means of managing pests in glandless cotton.