Abstract:
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.