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Egg parasitoids of the genus Trichogramma (Hym., Chalcidoidea: Trichogrammatidae) have been successfully utilized for biocontrol of several lepidopteran pests world‐wide. Trichogramma bournieri Pintureau and Babault and Trichogramma sp. nr. mwanzai Schulten and Feijen, which are native to Kenya and recovered from Chilo partellus eggs, were compared with the aim of evaluating them for field releases in Kenya for the control of lepidopteran pests, particularly Helicoverpa armigera and Plutella xylostella in tomato and kale, respectively. Age‐specific life tables were constructed at the Institute for Biological Control (BBA), Darmstadt, Germany in 1999 using a cohort of 60 mated females each at 26 ± 1°C, 70 ± 10% relative humidity and 16 h light : 8 h dark photoperiod. The adult female performance and population growth statistics with associated standard errors were computed. There was no significant difference in adult longevity between selected strains of the two species. Trichogramma sp. nr. mwanzai showed significantly higher cumulative as well as daily mean fertility (75.97 and 18.11, respectively) compared with T. bournieri (47.83 and 13.24, respectively), and the respective proportion of female progenies were 52 and 72%. The intrinsic rate of natural increase was 0.309 and 0.306, while the net reproductive rate was 35.16 and 31.22 for T. sp. nr. mwanzai and T.bournieri strains, respectively. The study has also shown that there is no significant difference in the intrinsic rate of natural increase and the net reproductive rate between the two native species. In summary, there is difference between the two strains in their parasitization potential but not in population growth potential. Consequently, no preference can be given to one species when selecting for mass rearing purposes. Adult female performance is superior in T. sp. nr. mwanzai than in T. bournieri. Hence, the former strain should receive particular attention in future studies.

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Behavioural responses of female Diadegma mollipla to volatiles from cabbage plants and host‐infested [Plutella xylostella (L.)] cabbage plants sprayed with two neem insecticide formulations were investigated in a Y‐tube olfactometer. Parasitoids were significantly more attracted to volatiles from cabbage and host‐infested cabbage sprayed with the powder formulation than to clean air. In contrast, parasitoid response to volatiles from cabbage and host‐infested cabbage sprayed with the oil formulation was not significantly different from clean air. In choice tests between infested plants sprayed with water (control) or the powder formulation, parasitoids showed no preference for volatiles from either of the treatments. In similar tests with the oil formulation, parasitoids showed a preference for volatiles from control plants over plants sprayed with the oil formulation. In host acceptance and suitability tests, parasitism rates in the neem‐ and water‐sprayed hosts were, with one exception, not significantly different. However, the neem‐sprayed larvae died earlier than control larvae and were therefore not able to support parasitoid development. The implication of these findings for the combined use of neem insecticides and parasitoids in the management of P. xylostella is discussed.

The life table statistics of six native Kenyan species/strains of Trichogramma and Trichogrammatoidea were established using a factitious host Corcyra cephalonica, Stainton (Lepidoptera: Pyralidae), at eight different temperatures (10, 15, 20, 25, 28, 30, 32 and 35 degrees C) and two humidity levels (40-50 and 70-80%). The objective was to select insects with superior attributes for augmentative release against lepidopteran pests in horticultural crops. Both temperature and humidity affected developmental time and life table parameters of the parasitoids but temperature played a more critical role. Developmental time was inversely related to temperature. The intrinsic and finite rates of increase increased with temperature up to 30 degrees C. Both net reproduction rate and intrinsic rate of increase were higher at the lower humidity. Temperature inversely affected generation time of parasitoid strains regardless of the relative humidity. Two strains of Trichogramma sp. nr. mwanzai collected from both low and medium altitudes and Trichogrammatoidea sp. nr. lutea from the mid-altitudes, were better adapted to both low and high temperatures than the other strains, as indicated by the high intrinsic and net reproductive rates, at both humidity levels. These three strains appear to be promising candidates for augmentation biocontrol against the African bollworm Helicoverpa armigera in Kenya.

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