Pollen as a source of food for egg parasitoids of the genus Trichogramma (Hymenoptera: Trichogrammatidae)

Abstract

The value of corn pollen as a food source for Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) was assessed in the laboratory by testing the effect of different pollen diets on the longevity, capacity of parasitism and other life-table parameters. T. brassicae females that fed on corn pollen and water (wet filter paper dusted with pollen) lived significantly longer (4.97 days) than females that fed on water alone (2.67 days), but significantly shorter than those feeding on honey alone (8.37 days) or corn pollen and honey (8.23 days), respectively, in the absence of host eggs. The presence of European corn borer eggs (Ostrinia nubilalis Huebner, Lepidoptera: Pyralidae) significantly increased longevity. With host eggs available, female T. brassicae that fed on corn pollen and water lived significantly longer (4.9 days) than on water alone (2.60 days), but significantly shorter than on honey alone (12.33 days) or corn pollen and honey (12.17 days), respectively. The cumulative lifetime fecundity was 82.53 offspring pupae when fed on pollen and water, which was significantly higher than 61.70 for water alone but lower than feeding on honey alone (95.70) or corn pollen and honey (99.97), respectively. Compared to water alone, corn pollen and water increased the net reproduction rate (R0), intrinsic rate of increase (rm), and finite rate of increase (λ), and reduced the doubling time (T2), but had no effects on the emergence rate, sex ratio, and mean generation time (Tc). In another set of experiments, 13 out of 30 females reduced the number of pollen grains offered to them. The average number of pollen grains utilized per female in this 48-h test 2.46±0.40 (mean±SE). Hence, T. brassicae used corn pollen as food that significantly increased longevity and fecundity of the tested females. Pollen and honey supplied a complete diet for T. brassicae, compared to pollen and water or water alone.