Abstract
Spoladea recurvalis F. is a major pest moth of amaranth (Amaranthus spp.) flowers worldwide, with a potential of causing complete foliage loss under severe outbreaks. Chemical insecticides are uneconomical for resource-poor farmers and pose health and environmental risks. Host plant resistance (HPR) to insects is an effective, economical and environmentally friendly alternative that is poorly understood and largely unexploited among traditional leafy vegetables. A total of 35 amaranth accessions were evaluated for the expression of their antixenotic and antibiotic traits against S. recurvalis, focusing on their effects on the biology of the pest in comparison with a susceptible accession. The accession VI036227 was found to be highly resistant against the pest, exhibiting exemplary antibiosis by causing 100% larval mortality within the first 36 h, despite not being deterrent for oviposition. The accessions VI048076, VI056563 and VI047555-B demonstrated moderate resistance against the pest for specific parameters including low oviposition, moderate early stage larval mortality and reduced adult longevity. Total mortality and weight gain in these three accessions were, however, not significantly different from the susceptible control. Higher numbers of eggs were laid in no-choice compared to choice situations. The implications of these findings in the management of S. recurvalis on amaranths are discussed.
Highlights
Amaranth plants, in the genus Amaranthus L. and family Amaranthaceae, are traditional leafy vegetables (TLVs) that are largely consumed in several countries around the world, as vegetables and as grains [1,2]
The smallest leaf sizes were recorded on accession VI036227 with width of 1.2 ± 0.1 cm and length 3.2 ± 0.7 cm compared to 10.6 ± 0.6 and 19.3 ± 2.2 cm in the susceptible accession
Larval development was completely hindered on accession VI036227, resulting in 100% larval mortality and points to presence of potent antibiosis
Summary
In the genus Amaranthus L. and family Amaranthaceae, are traditional leafy vegetables (TLVs) that are largely consumed in several countries around the world, as vegetables (leaves) and as grains [1,2]. Arthropod pests and diseases present a major challenge to optimum productivity of amaranths in several regions of the world including Africa [11,12,13,14], Asia [15] and the Americas [7,16,17]. More than 250 species of insect pests have been reported to feed on amaranth worldwide, with a majority (50%) falling in the category of leaf chewers/defoliators [11,16,17,18]
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