[Evaluation of plant protectants against pest insects]

An interference index of population control (IIPC) was constructed for investigating the complex effects of plant protectants, including the effects of repelling insect pests away from the plant, deterring the egg laying of adults and the continuation of feeding, and causing death by toxicity. At the same time, indicated by IIPC, the alcohol extracts of some common plants, such as Eucalytus rubusta, Wedelia chinensis etc. and the neem oil gave very good results to protect the plant against Plutella xylostella. The D-C-Tron NR Petroleum Spray Oil (CALTEX) also gave an excellent effect to protect citrus against red mite. All the experiments show the important role of the repellent effect on the pests.