CHARACTERIZATION OF GRAIN AMARANTH LINES AND EVALUATION OF SOME AQUEOUS PLANT EXTRACTS FOR CONTROL OF CLETUS FUSCESCENS WALKER.

Abstract

The morphological characterization of the 93 accessions of Amaranthus spp based on 8 quantitative traits analysed for cluster and principal components analysis revealed that the first four PCs with eigenvalues >1 explained 93.12% of the variability amongst 30 introduced accessions. The variance explained by PC1 was due to Cletus fuscescens infestation and viability percentage. PC2 originated from 1000 seed weight and yield/ plant. Cluster analysis grouped the germplasm into 3 clusters. Amongst the 62 repartriated accessions the first two PCs explained 71.91% of the variability. The variance explained by PC1 was due to viability percentage, C. fuscescens infestation and yield / plant while that of PC2 was due to leaf width. Cluster analysis grouped the germplasm into 2 major and 1 minor cluster. A total of 84 species of insects belonging to 8 orders and 24 families were found. The insect in order of abundance were coleopterans (36.90%), lepidopterans (29.79%), heteropterans (15.48%) with the dermapterans and the dipterans (1.19%) each. Among the natural enemies the heteropterans were the most abundant and belonged to the reduviidae. The hymenopteran parasitoids were all ichneumonids. The major leaf eating larvae were Hymenia recurvalis Fabricius, Psara bipunctalis Fabricius and Psara palpalis Hampson all from pyralidae. The major stem borers were Baris circumscutellata Hustache, Gasteroclisus rhomboidalis Boheman, Leucogrammus paykulli Boheman, Lixus camerunus Kolbe, Hypolixus nubilosus Boheman and Hadromerus sagittarius Olivier all belonging to curculionidae. The major grains sucking bugs were the coreid Cletomorpha unifasciata Blote and C. fuscescens Walker, and the pentatomid Aspavia armigera Fabricius. The 3 accessions with intermediate inflorescence density index had highest C. fuscescens populations/ plant and least viability percentage while all the 3 accessions with dense inflorescence density index had lowest C. fuscescens populations/ plant and highest viability percentage. C. fuscescens populations/ plant correlated negatively with only viability percentage. Also stepwise regression analysis selected viability percentage as the most powerful variable reflecting C. fuscescens infestation. Decrease in plant spacing resulted in increase in C. fuscescens infestation and decrease in viability percentage and yield/ plant. A thousand seed weight was not affected by spacing but only by genotype. Close spacing recorded higher estimated yield/ ha. C. fuscescens population levels started increasing when seeds began to form on the head of the amaranth and population levels generally peaked when the seeds were completely formed but milky. The individual effects of lines and phenological stages of grain amaranth significantly (p≥0.05) affected C. fuscescens population levels and planting dates was a predominant factor. The interaction between planting dates and phenological stages of grain amaranth was observed to be the most important factor in 2009, while planting dates and lines were the most important factors affecting the population build up of C. fuscescens on grain amaranth in 2010. C. fuscescens control, viability percentage and yield/ plant were significantly (p≥0.05) enhanced in treated plots compared with the untreated ones. The synthetic insecticide (cypermethrin) was however superior to the botanicals: garlic-pepper, Momordica charantia and Xylopia aethiopica in all the parameters tested. A thousand seed weight was not affected by any of the treatments.