Each week, we pick a question that we get through our Master Gardeners hotline and write an article for the popular, online magazine Rural Intelligence. Below is this weeks article.
This week we got a question from someone who can’t seem to keep powdery mildew out of their vegetable garden, particularly on their squash and cucumbers. When you think of garden pains, this is certainly one of the most common, and it doesn’t just impact veggies — in my garden I always seem to have a problem with it in regards to phlox and bee balm.
Thankfully, there are steps that you can take to tackle mildew. You should start by trying to avoid the problem altogether by taking preventative measures. If you are planting in the same spot as last year, remove all of the dead plant material instead of tilling it under the soil. Next, when purchasing your seeds or seedlings, try to pick a cultivar that is known to be resistant to disease and avoid planting in the shade.
Once you have seedlings in the ground, it is recommended that you mulch — mildew is a spore that comes from the soil, and mulch can often suppress its spread. You’ll also want to be careful as to how you water. Try not to splash the leaves; water at the base of the plant (as with drip irrigation), not from above, and avoid over-watering.
If you do notice powdery mildew forming on your plants, remove the affected areas immediately. You also might want to try thinning out the plants with selective pruning; often mildew can start forming when there isn’t adequate air flow through the plant. We also recommend a baking soda spray that you can make at home by mixing one gallon of water with one tablespoon of baking soda, two tablespoons of vegetable oil, and one tablespoon of liquid soap (such as hand soap). Use this spray every two weeks.
If the problem still persists, it might just be possible that it isn’t powdery mildew at all. There are some insects that can cause powdery mildew-like symptoms — take a close look at your plants and look for any signs that could indicate pests just to make sure.