Influence of time of introduction and proportion on the efficacy of grain amaranth trap crop against Aulacophora foveicollis and Epilachna chrysomelina on cucumber (Cucumis sativus L.)

Abstract A field experiment was conducted in the early and late planting seasons, 2019 to evaluate the effectiveness of grain amaranth (Amaranthus cruentus L.) planted at different timing and proportion as a trap crop for reducing insect pest densities on cucumber. Amaranth was established into cucumber plots two weeks before cucumber (2WBC), same day (SD) with cucumber or two weeks after cucumber (2WAC) in 100:0, 100:25, 100:50, 100:75 and 100:100 cucumber-amaranth proportions. Amaranth planted 2WBC or SD trapped significantly higher numbers of Aulacophora foveicollis and Epilachna chrysomelina compared to 2WAC, corresponding to lower infestations and damage on cucumber, with the highest fruit yield at SD cucumber. While leaf damage was reduced by 68–74% at 100:100, yield increase of 66–69% was obtained at 100:50 relative to sole cucumber plots. Hence, planting grain amaranth SD with cucumber at 100:50 cucumber-amaranth proportion has a great prospect against insect pests of cucumber in a trap–cropping strategy.