Harmful symptoms:
The aphids that harm melons and vegetables are mainly melon aphids. Adults and nymphs suck juice on the back of melon leaves and tender stems. After the young leaves and growth points are killed, the leaves shrink, the growth stagnates, and even the whole plant withers and dies; Old leaves do not shrink when they are injured, and dry up ahead of time.
Occurrence law:
Aphids are very fertile, 1 year can reproduce 10-30 generations, and the generations overlap prominently. When the 5-day average temperature rises to above 12℃ steadily, breeding begins. In early spring and late autumn when the temperature is low, it takes 1 generation 10 days to complete, and it only takes 4-5 days in warm summer. The temperature of 16-22℃ is most suitable for aphid breeding, and drought or excessive planting density is beneficial to aphid damage.
Prevention and control methods:
1. Before seedling raising, thoroughly fumigate and kill the residual aphids, clean up weeds and residual plants, add nylon yarn to the vent, control the source of exotic insects, and cultivate "insect-free seedlings". Avoid the mixed planting of cucumber, tomato and kidney bean, so as not to create a good living environment for aphids and aggravate the harm.
2. Physical prevention. Aphids have a strong trapping effect on yellow. Setting yellow boards (10. 17m fibreboard or cardboard, painted orange and coated with a layer of sticky oil, 32-34 pieces per mu) in the greenhouse has obvious trapping effect on adults. The yellow board should be set in the row with the same height as the plant, and it should be smeared with oil (usually mixed with a little butter) every 7 ~ 10 days to prevent oil droplets from burning crops.
3. Chemical control. 46% flonicamid acetamiprid water dispersible granules can be 800~ 1000 times; Or 16% spinosad acetamiprid suspension concentrate 15 ~ 20ml/ mu; 20% pymetrozine clothianidin suspension 20-40g/mu; Or 75% pymetrozine spirodiclofen water dispersible granules 90 ~ 135g/ha.