Question: Some of my cucumbers have odd shapes and the leaves have dry yellow spots on them. Is there anything I can do?
Answer: One possibility is that the cucumbers have thrips, a common insect pest of cucumbers. If your plants look like the ones in today’s photos, you probably have thrips feeding on the leaves and fruits.
Thrips are very small insects that feed by piercing and sucking plant fluids out of leaves. They will also cause some damage by feeding on the cucumbers if the thrips population is very high. This feeding can leave silvery streaks on the skin of the cucumber or even cause the fruit to be deformed.
Thrips can be controlled with regular spraying of insecticides. For organic gardeners, insecticidal soap, neem oil or Spinosad are effective.
Thorough coverage is always important. Spray the entire plant, not just the affected leaves, because you want to provide protection to new leaves as they emerge. Don’t apply any soap or oil-based spray when your plants are drought-stressed or when you know temperatures will rise above 90 degrees before the spray can be completely dry. Oils also shouldn’t be applied within two weeks of a sulfur spray. Spinosad should be sprayed in the evening so it will be completely dry before bees begin foraging in the morning.
Good weed control in the spring and throughout the gardening season, plus a thorough fall cleanup are also important.
Question: It seems too early in the year, but there are already white mold spots on my squash plants. What is the best way to save my plants so that I can still get squash?
Answer: The summer has flown by, and the powdery mildew season is in full swing. It’s been showing up in local gardens for several weeks now. Powdery mildew is such a common disease in vegetable gardens that it would be surprising if gardeners weren’t seeing it on at least some plants. Unlike the fungal diseases that show up during cool, wet spring weather, powdery mildew thrives in the warm, dry conditions that we have during the summer.
There are many different species of fungi that cause powdery mildew and each species affects only certain plants. The powdery mildew that you see on your roses or maple trees isn’t the same powdery mildew that attacks your squash.
Prevention is the best method of control for powdery mildew. There are many resistant vegetable varieties available. When you’re preparing to purchase seeds, look for “PM” in the variety description.
For this year, begin protecting your plants with a fungicide. There are many different brand names and active ingredients available. Look for a product that is labeled for use in vegetable gardens. The label should also include powdery mildew in the list of controlled diseases. If you are trying to garden organically, you can try neem oil or potassium bicarbonate. Don’t apply any oil-based spray when your plants are drought-stressed or when you know temperatures will rise above 90 degrees before the oil will be completely dry. Oils also shouldn’t be applied within two weeks of a sulfur spray.
Fungicides are most effective when applied at the first signs of powdery mildew infection. Any fungicide will need to be applied on a regular schedule to keep the disease under control. The label on the product will tell you how often you should apply the spray. Thorough coverage is always important. If you’re diligent, you should be able to enjoy squash for several more weeks.
Remove and dispose of any severely affected leaves. This fall do a good cleanup job in the garden. Don’t leave any infected plant material over the winter.