Relative abundance and impact of insect pests on watermelon fruit yield in a rainforest environment

In the rainforest zone of Nigeria, published information on the composition, relative abundance and population densities of different pests on watermelon is limited. This study was carried out to determine the insect pests associated with watermelon, their relative abundance population densities and induced yield loss at different crop growth stages. The watermelon plants were protected with weekly applications of lambda-cyhalothrin at pre-flowering, flowering, post-flowering/fruiting, or throughout the growth period (full protection), while control plots received no protection. Insect pests found were Aulacophora nigripennis Motschulsky, 1857, Aulacophora hilaris (Boisduval, 1835), Aulacophora indica (Gmelin, 1790), Aulacophora africana (Weise, 1903), Phyllotreta cruciferae (Goeze, 1777), Epilachna chrysomelina (Fabricius, 1787) and Coridius viduatus (Fabricius, 1794). The yield of watermelon on the three varieties across the different stages of protection differed significantly from each other in both seasons. Full-protection plots significantly produced more fruit yield, followed by protection-at-flowering, protection-at-post-flowering, and protection-at-pre-flowering, while no-protection plots produced the least yield. The protected-at-flowering plots recorded the lowest percentage in yield reduction, while yield reduction in the remaining different stages of protection were more than 50 % in both seasons making the flowering stage the critical stage of protection.