Effect of mulching on diversity and abundance of natural enemies associated with brinjal (<em>Solanum melongena</em> L.) crop in Mawathagama, Kurunegala (IL1)

Abstract

Misuse of insecticides has negative impacts on the environment and human health; hence, a search for non-chemical alternatives for insect pest control is a timely need. Natural enemies play a significant role in suppressing insect pest populations in crops. Mulching has an impact on the diversity of natural enemies in soil, but it has not been adequately documented locally. Thus, this study was conducted to examine the influence of mulches on natural enemies associated with the pests of the brinjal crop. Four mulch materials viz. rice straw, gliricidia (Gliricidia sepium) leaves, weed residues, and black colour polythene, as the treatments, were laid on plots of brinjal crop. Unmulched plots, with and without weeds, were also used as controls. Experimental design was RCBD with three replicates. Soil inhabitants were caught using pitfall traps and soil sampling was undertaken up to 10 cm depth. Foliage insects were collected using sweep netting. The total number of natural enemies significantly (F (5,120) = 5.928, P<0.05) varied between the treatments. The highest mean number of natural enemies was recorded in rice-straw mulch (2.50 plot -1 ), followed by weed residues (1.19 plot -1 ), gliricidia (1.10 plot -1 ), and black polythene (0.10 plot -1 ). Unmulched plots left with weeds had a higher mean number of natural enemies (1.29 plot -1 ) than the plots without weeds (0.43 plot -1 ). Pest abundance was significantly (F (5,120) = 3.897, P <0.05) different between treatments. The highest abundance was recorded in unmulched plots (25.30 plot -1 ), followed by weed residues (7.95 plot -1 ), gliricidia (7.76 plot -1 ), straw (6.50 plot -1 ), and black polythene (2.0 plot -1 ). The study concluded that rice-straw mulching favours natural enemies, while black polythene reduces insect pest abundance. Further, the presence of weeds on plots enhances the abundance of natural enemies.