Repellent effect of non-host vegetables and their extracts on Pieris rapae L.

To evaluate the control effects of non-host vegetables on imported cabbage butterfly Pieris rapae, bioassays were conducted to investigate the repellent effects of 6 non-host vegetables such as tomato (Lycopersicon esculentum), fennel (Foeniculum vulgare), catnip (Nepeta cataria), lettuce (Lactuca sativa), coriander (Coriandrum sativum) and towel gourd (Luffa cylindrical) on the butterfly in laboratory and field experiments. Indoor bioassay results show that selection response percentage of adult butterfly to cabbage reduces after treated with non-host vegetable extracts. The selection response percentages of mated female butterfly to cabbages treated with catnip, fennel, tomato and lettuce extracts are particularly low, only 3.67%, 4.30%, 5.27% and 8.26% respectively. Egg numbers laid by adult butterflies in cabbage seedlings treated with non-host vegetable extracts significantly reduce as well. Repellent activities of tomato, fennel and catnip extracts are strongest. After one day of treatment, the percentages of no-choice oviposition repellent are 91.04%, 75.54% and 71.67%, and those of choice oviposition repellent are 94.64%, 79.66% and 78.96% respectively. Field test results show that the amount of butterfly eggs in per cabbage plant could drop by 68.80%, 62.62% and 55.09% respectively in intercropping filed of cabbage with tomato, fennel and catnip. Effective repellent distances of the three non-host vegetables are 4 m, 2 m and 2 m respectively. Therefore, imported cabbage butterfly could be repelled by intercropping non-host vegetables or spraying not-host vegetable extracts in the cabbage fields.