Impact of trichome density on the infestation of Aphis gossypii Glover and incidence of virus disease in ashgourd [Benincasa hispida (Thunb.) Cogn.]

The resistance of ashgourd to the melon-cotton aphid, Aphis gossypii (Glover), and the incidence of aphid-transmitted viral diseases was investigated following recording of aphid numbers and trichome (plant hair) numbers per cm(2) of leaf on four parts of the cucurbit, ashgourd, representing four genotypes (Local Sylhet, Local Round, High Female and CQ-10-90). The Local Sylhet genotype was found to have the highest trichome density compared with those of Local Round, High Female, and CQ-10-90 ashgourd genotypes, and was least infested by Aphis gossypii. The percentage of virus-infected plants was also found to be lowest on the Local Sylhet genotype. Aphid numbers were lowest on the terminal and young leaves of ashgourd compared with mature and senescent leaves, due to the higher trichome density in the former leaf categories. Trichome density was found to have a significant negative influence on the number of aphids. Trichomes in ashgourd play a major role by providing a first line defence in reducing aphid infestation, with a subsequent beneficial effect of reducing the incidence of virus.