Do you have powdery mildew on your squash plants?
Do you struggle with powdery mildew on your squash, pumpkins and cucumbers later in the season? Well, don't fret, it is very common. Powdery mildew occurs when the soil is too dry or has inconsistent moisture – however, it is also natural as the plants age towards the end of the season. Powdery mildew is normal, and happens to nearly all cucurbit plants (squash, cucumbers, pumpkins, zucchini) at some point towards the end of the season.
The best thing you can do to prevent powdery mildew on squash plants is to keep the soil moisture consistent. Squash and all cucurbits have a low root-to-shoot ratio, so they dry out quickly if the soil dries out causing the plant stress resulting in wilting, dried out or yellowing leaves, and powdery mildew appears.
The best way to prevent stress is watering consistently, and putting down a good layer of mulch around your plants to help keep soil moisture consistent.
Good mulches include:
- untreated grass clippings
- weed-free straw
- compost
- shredded leaves
When using mulch, make sure to water deeply and check the soil moisture to make sure the water is getting deep into the soil mound. Be sure not to pile mulch up on the stem, as this can cause stem rot.
Ideally, water the soil and avoid getting a lot of water on the leaves (though this is nearly impossible in the peak of the season if you are hand-watering!) But know that even if you have a drip irrigation, powdery mildew can appear later in the season, it's quite normal and nearly inevitable with squashes and pumpkins!.
What can you do for Powdery Mildew?
When you do start to see powdery mildew, you can prune out affected leaves to increase airflow and allow for new growth.
What about Milk for treating Powdery Mildew?
Some people suggest using watered down milk and spray the leaves to prevent or treat powdery mildew. We tried it once but it didn't seem to help, perhaps because we weren't doing it often enough (it's a chore!) It seems like a hassle, and probably just a waste of milk. But there are people who say it works great, so perhaps it does when used well.
Our Best Tip for Powdery Mildew:
For your sanity, just be aware that powdery mildew will likely show up on your squash, pumpkin zucchini and cucumber plants later in the season. Try to keep them consistently watered and well-mulched to put it off as long as possible.
One solution to powdery mildew: You can also plant seeds for some of the fast growing cucurbits like cucumbers, yellow squash and zucchini in the mid-summer for a second round of healthy crop, so they start coming in strong as the early planted cucurbits age and slow down or stop producing, and/or start getting a lot of powdery mildew.
