You may have powdery mildew on your vegetables.  If you could send a photo of the mold, that would be very helpful.  But, based on your description, it sounds like powdery mildew.  Insecticides will not help with powdery mildew which is a fungal disease.  The best way to fight a fungal disease is to prevent it from happening. Before the disease appears foliage can be treated with an appropriate fungicide.

Here are some practices to start this year.

• Make sure you remove powdery mildew infected plant residue as it appears. You can safely add it to the compost pile or burn it (check burning restrictions in your area).
• Some practices start before you plant. When you are ordering seeds and picking out plants, look for powdery mildew resistant varieties. These varieties are available in many vining vegetables and some flower varieties and make a big difference.
• Test your soil. This will enable you to apply the right amount and right type of fertilizer to your garden. Plants that are over-fertilized produce a lot of foliage and become overly bushy and extra susceptible to powdery mildew. Applying the right amount of nutrition is a win for the environment and your wallet.
• As you plant and care for next year’s garden, think about airflow as you lay out the garden. All plant diseases love the wet leaves that poor airflow provides. Space plants based on their mature size. Doing so not only reduces disease issues, but makes weeding easier, and allows more light to reach stems, producing better bloom and fruiting.

Author: Marissa Schuh, Extension educator, integrated pest management
Reviewed by Julie Weisenhorn, Extension educator, horticulture

Powdery mildew in flowers and vining vegetables | UMN Extension