Parasitism of Bollworm (Lepidoptera: Noctuidae) Eggs on Nectaried and Nectariless Cotton

Field and laboratory studies were conducted to quantify impact of nectariless cotton on parasitism of bollworm, Heliothis zea (Boddie), eggs by egg parasite Trichogramma pretiosum Riley. Results from a small-plot field test of a single cohort of T. pretiosum showed a 3.3-fold decline in percentage of H. zea egg parasitism during a 2-d period on a nectariless cotton (72.3% on day 0 to 22.0% on day 2), whereas the decline was only 1.5- fold during the same period on nectaried cotton (74.7%on day 0 to 48.3% on day 2). In a large-plot field study, seasonal H. zea egg parasitism by naturally occurring Trichogramma spp. was ca. 16%lower on a nectariless cotton compared with a nectaried cultivar. A laboratory bioassay showed that T. pretiosum females given a honey/nectar mixture lived 3-fold longer than parasites held without the mixture, regardless of presence or absence of host eggs.