Answer: There's no magic formula for controlling all insects on all plants (sometimes I wish there were!) so your best approach is to identify the pests and then use something that targets that particular pest. For instance, roses usually are plagued with aphids, which are soft bodied insects. These pests can be controlled by either a strong stream of water from the hose, or by spraying with Insecticidal Soap (use according to label directions). Since aphids give birth to live young you can have several generations feeding on a plant in a matter of just a few days. Because of this, you'll need to be on the look out for new populations and treat them as quickly as possible. Mold can mean powdery mildew or black spot, both of which attack roses. Powdery mildew usually indicates conditions which are too shady, and poor air circulation. It usually attacks plants when nights are cool and days are warm. You can't do anything about the weather, but you can make sure your plants get at least 8 hours of direct sunlight each day and you can prune to open the plants up to better air circulation. Since this is the end of the growing season, you can help stop the spread of fungal diseases by cutting off the affected plant parts and removing them from the garden.
Hope this information is helpful!
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