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.

Performance of the newly identified endoparasitoid Cotesia icipe Fernandez‐Triana & Fiaboe on Spodoptera littoralis (Boisduval)

“…This is in line with Othim et al. () who reported that experience can increase the responsiveness of Apanteles hemara Nixon (Hymenoptrea: Braconidae) on S. recurvalis and U. ferrugalis .…”

“…Host larval mortality in the presence and absence of the parasitoid were calculated as described by Othim et al. ().…”

“…Amaranth crop production is seriously hampered by a complex of insect pests of which lepidopteran defoliators are the most destructive. The most important species include Herpetogramma bipunctalis (F.) (Lepidoptera: Crambidae), Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), Pholisora catullus (F.) (Lepidoptera: Hesperiidae), Spoladea recurvalis (F.) (Lepidoptera: Crambidae), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), Spodoptera eridania (Stoll) (Lepidoptera: Noctuidae), Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) and Udea ferrugalis (Hübner) (Lepidoptera: Crambidae) (Ellis, ; Othim et al., ). Herpetogramma bipunctalis and S. recurvalis are leaf webbers, whereas the other Spodoptera species are leafworms.…”

“…In Kenya, lepidopteran defoliators are an increasingly serious constraint for sustainable amaranth production (Kahuthia-Gathu, 2011). A recent countrywide survey carried out in Kenya during the long raining season of 2014 revealed that lepidopteran defoliators, including S. littoralis, are the most devastating pest of vegetable amaranth, causing foliage damage ranged between 20% and 40% (Othim et al, 2017). This pest belongs to the genus Spodoptera, which includes several economically important species in Africa (Brown & Dewhurst, 1975) that attack various cash and traditional food crops (Capinera, 2008;Khedr, AL-Shannaf, Mead, & Shaker, 2015).…”

Acceptability and suitability of Spodoptera exigua (Hübner) for Cotesia icipe Fernandez‐Triana & Fiaboe on amaranth

“…Dropping to the ground using the silk thread to avoid parasitoid attack is a typical defensive behaviour in many lepidopteran larvae: Udea ferrugalis (Hübner) (Lepidoptera: Crambidae) and Spoladea recurvalis (F.) (Lepidoptera: Crambidae) exposed to Apanteles hemara Nixon (Hymenoptera: Braconidae) (Othim et al., ) and Plutella xylostella (L.) (Lepidoptera: Plutellidae) larvae exposed to Diadegma semiclausum Helen (Hymenoptera: Ichneumonidae) and C. plutellae (Wang & Keller, ) display the same behaviour. The strategy used by C. icipe which involved pursuing the host pest has been reported in C .…”