The aster flower has a number of pests and diseases it is susceptible to during its growing season but can be prevented through the use of pesticides and fungicides.
The main pests that can attack the aster plant and consume its leaves are aphids, leafhoppers, spider mites, thrips, whiteflies, weevils, and scales. If the mature aster plant starts to reveal leaves that have been eaten by any of these insects, a pesticide shouldbe used to prevent further damage. Scales can be hard to spot as insects; look for any silvery gray scales on the stem of the aster plants. Pesticides can keep the scales under control.
The most damaging disease to asters is stem rot, which is caused by a fungus that can begin at the start of the germination process. The seeds that have remained damp in the ground develop the fungus, which remains with the plant but cannot be detected until the plant reaches maturity. As a result, the plant does not blossom and dies early. Preventing fungus and stem rot is the key to maintaining healthy aster plants. Prevent overwatering when the seeds germinate and make sure the soil is well drained.
Powdery mildew can also affect asters. As with the fungus, prevention by allowing the plant to receive an adequate amount of sunlight will keep the asters from remaining damp constantly.