Asymmetry Effect of Intercropping Non Host Crops between Cabbage and Climatic Factor on the Population of the Diamondback Moth (Plutella Xylostella L.) and Yield

Diamondback Moth (DBM) is one of the major constraints for the profitable production of cabbage in Cameron Highlands, Malaysia. The loss in yield of cabbage caused by DBM could reach up to more than 80% if a severe infestation occurred in the field. Due to that problem, farmers in Cameron Highlands are preferred to apply the broad spectrum of synthetic insecticides rather than implementing other pest management strategies. The demand for insecticides in Cameron Highlands seems endless until today, but more aggressive. This paper highlighted the possibility of implementing intercropping cabbage with seven treatments in reducing adults and larvae populations of DBM in the polyculture system. The distributions of adults and larvae population of DBM against the factors of temperature and rainfall also have been addressed in this study. A total of seven treatments was implicated, including onion (Allium cepa L.), tomato (Solanum lycopersicon L.), marigold (Tagetes erecta L.), citronella grass (Cymbopogon nardus L. rendle), and mosquito plants (Pelargonium citrosum) which arranged in Randomized Complete Block Design (RCBD). The results indicated that insignificant variations (P>0.05) were observed among the population of adults and larvae at all seven treatments tested compared with the control. Moreover, adults and larvae of DBM were negatively correlated with temperature and rainfall factors. The results also showed that a critical period of DBM infestations was detected in the pre-heading stage (< 30 DAT). In terms of performance among treatments, our finding also has shown that mosquito plant was the best treatment acted as a repellent, however mosquito plant treatment contributed to the lowest yield due to the competition of plant growth resources and its wider canopy structure.