Entomologia, ornitologia e herpetologia: pesquisas atuais
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Occurrence, Abundance and Control of the Major Insect Pests Associated with Amaranths in Ibadan, Nigeria

Aderolu IA, Omooloye AA and Okelana FA

Beetworm Moth (BM), Hymenia recurvalis F. is a major defoliator of Amaranthus species causing severe yield loss. Control with synthetic insecticide is being discouraged for its adverse effects. Information on sustainable management of BM with ecologically friendly methods is scanty. Three Amaranthus species: A. cruentus, A. blitum and A. hybridus were evaluated for insect diversity and abundance during wet and dry seasons of two years following standard procedures. Data collected were Leaf Area Damage (LAD) (cm2); Infestation per plant (I) and Field Abundance (FA). Three neem extracts: 0.125 g Aqueous Neem Leaf (ANL) w/v; 0.125 g Aqueous Neem Bark Ash (ANBA) w/v and Aqueous Modified ANL+ANBA (AMAN) (1:1) all at 3l/25 m2 were bioassayed against BM using λ-cyhalothrin at 2.5 ml/25m2 and water as controls. Data collected were analysed using descriptive statistics, ANOVA at P>0.05, Shannon index (H), Simpson index (1-D) and evenness. Sixty insect species from 29 families and 12 orders; comprising 31 defoliators, 12 predators, one pupa parasitoid (Apanteles hymeneae) and 16 non-economic species were encountered on Amaranthus species. The BM was the most damaging causing 69.4 ± 0.16% loss of foliage compared to control. The species abundance in both seasons was BM (2916.8 ± 138.83)>Hypolixus truncatulus (2262.7 ± 94.1) >Lixus truncatulus (2088.7 ± 36.4). Shannon (3.52), 1-D (0.96) and evenness index (0.65) of diversity were high with few dominant species. The AMAN at 3l/25 m2 w/v extract caused significant reduction of leaf damage (72 ± 0.05%) and field infestation (78 ± 0.06%) compared to the untreated control; but comparatively less effective by only 5% to λ-cyhalothrin; implying suitability as environmentally safe control measure.