Rape aphid

The main aphids harmful to rape are radish aphid (Lipaphis erysimi), peach aphid (Myzus persicae) and cabbage aphid (Brevicoryne 6rassicae). Radish aphid and peach aphid are common in all provinces (regions) of China. These three kinds of aphids often mix on rape and use needle-like mouthparts to prick the juice on the back of the leaves or the heart of Chinese cabbage, which makes the leaves curl and stagnate, and in serious cases, the whole plant turns yellow and dies. Aphids also spread viral diseases, causing greater losses. [morphological characteristics] the wingless female aphid of radish aphid is 1.8 mm long and yellowish green. On the back of the abdomen, there are dark green horizontal lines on each segment, a vertical row of small black spots on each side, and 3 hairs on each side of the tail. The wingless viviparous female aphids of peach aphids are 1.4 Mel 1.9 mm long, ovoid, yellowish green, reddish brown, orange, etc., and the abdominal tube is black and slender cylindrical. The wingless viviparous female aphid of cabbage aphid is 2.5 mm long, dark green, covered with white powder, and there are intermittent transverse bands on the back of the abdomen. The ventral canal is black, short and thick, and the middle part is significantly dilated. [occurrence regularity] more than 40 generations occurred in a year from north to south. In North China. Radish aphid overwinters on stored vegetables with eggs and peach aphids on peach branches. The behavior of cabbage aphid is similar to that of radish aphid. It is the peak period of migration and diffusion of radish aphid and peach aphid when rape is sown in autumn. Generally, radish aphids migrate first and then peach aphids. The occurrence of radish aphids is more than that of peach aphids. When it is rainy in autumn, peach aphids can exceed radish aphids. In winter, radish aphids clustered in the heart leaves of rape, while peach aphids scattered on the back of rape leaves near the ground. In the following spring, after bolting, the two kinds of aphids gathered in the flower buds of the main branches, and then dispersed to the pedicels and pods of each branch. the number increased sharply in late spring and early summer, decreased in summer, and increased again in autumn. Early sowing rape suffered heavily in dry years, and natural enemies such as ladybugs, aphid flies, lacewings and aphid cocoon wasps had great control effect on aphids. [control methods] 1. Agricultural measures to select good varieties of insect resistance; before the migration of aphids in autumn, remove weeds and fallen leaves of residual plants in the field to reduce the number of insect population. 2. when the rate of aphids in rape seedlings is up to 10%, or the rate of aphid buds in bolting stage is up to 10%, spraying 2000-3000 times of aldicarb can effectively eliminate aphids without harming natural enemies. It can also be sprayed evenly with 1500 times of 80% dichlorvos, 2000 times of 5% efficient cypermethrin cheese, or 1000 times of 40% dimethoate.