Performance of Apanteles hemara (Hymenoptera: Braconidae) on two Amaranth Leaf-webbers: Spoladea recurvalis and Udea ferrugalis (Lepidoptera: Crambidae)

Abstract

Amaranth is an African indigenous vegetable that is gaining popularity due to its nutritional, medicinal, and economic values. In East Africa, frequent outbreaks of Lepidopteran leaf-webbers, Spoladea recurvalis F. (Lepidoptera: Crambidae) and Udea ferrugalis Hübner (1976) are reported on this crop, causing up to 100% foliage loss. The larval endoparasitoid Apanteles hemara Nixon is also frequently found associated with these pests during the outbreaks, however, its performance on both pests has never been documented. Laboratory studies were therefore carried out to assess the acceptability and suitability of S. recurvalis and U. ferrugalis to A. hemara. Both leaf-webber species were accepted by and suitable for the parasitoid. The mean host searching time and oviposition attempts were neither affected by rearing host nor test host. The total developmental time of A. hemara ranged between 10.6 ± 0.16 and 12.8 ± 0.30 days on both hosts. The sex ratio of the parasitoid was female biased when reared on S. recurvalis but male biased on U. ferrugalis. When offered 50 larvae of leaf-webbers for 24 h, a single female A. hemara achieved parasitism rates from 42.63 ± 5.80 to 44.55 ± 5.95, while a cohort of five females resulted in parasitism rates between 87.25 ± 2.70 and 94.67 ± 1.98 %. There was no significant difference between hosts in regard to progeny fitness at each parasitoid density. The parasitoid also caused significant nonreproductive larval mortalities in the hosts. The implications of these findings for mass rearing of the parasitoid as well as for conservation and augmentative biological control of amaranth lepidopteran leaf-webbers in East Africa are discussed.

Keywords: Acceptability; biological control; nonreproductive mortality; parasitism; suitability.