Q. I had issues with my cucumber plants last year. My plants developed powdery mildew. I also had fruits that were misshapen and yellow. My friends on social media have suggested I remove the top 2-3inches of soil, add calcium to the soil, use neem oil, and spray the plants with baking soda or milk. What should I do?
A. Even though some may disagree, I think cucumbers are tough to grow in our area, because they have a myriad of diseases and insect pests. Powdery mildew is just one of the many fungal leaf diseases cucumbers can have.
Whenever one deals with a crop that has many disease and insect issues, one should first think of crop rotation and sanitation in the garden. Rather than remove soil, rotate the plants to different areas of the garden each year. Clean up debris in the garden so that insects and diseases do not overwinter to cause issues the following season.
Pick disease- and insect-resistant cukes to grow – many websites and seed companies list resistant cultivars.
Grow your cucumbers in an area amended with Canadian sphagnum peat, aged manure and compost with at least eight hours of direct sunlight (morning sun is best). Have the plants grow up a trellis or screen for better air circulation. We have tons of calcium in our soils, so generally it is not needed.
It is almost mandatory to use row covers to protect the cucumbers against their insect nemesis – the spotted or striped cucumber beetle which spreads bacterial wilt. Aphids also spread fatal bacterial and viral diseases to cukes. ReMay is an excellent row cover material available locally and online to cover cukes after planting.
The covers must be removed when the plants begin to flower as beneficial insects are needed for pollination and fruit set. The best companion plants for cucumbers are basil, broccoli, and dill, and most flowers or herbs which attract insects.
Powdery mildew is a common disease of plants in the cucumber/squash family. This fungal disease is primarily blown about by the wind, so one never escapes the threat of the disease. Keep the soil evenly moist and never water in late afternoon or evening.
Studies have shown that sprays of milk or baking soda either don’t work very well, or don’t work at all.
Neem can help with fungal and insect pest issues but can damage plants when applied in hot and sunny conditions. Foliar sprays of compost tea have been shown to reduce fungal infections in some plants. Serenade Garden Fungicide can be an effective organic control for mildew.
Generally, yellow misshaped fruits are caused by improper pollination, or by hot and very dry conditions. Remember to dig near the plants and water when the soil at the 8-inch depth is dry.
Growing cukes in our area can be challenging. If you manage to get two crops of cucumbers in the course of a year, you are doing well.
The Plant Medic, written by Ricky Kemery, appears every other Tuesday. Kemery retired as the extension educator for horticulture at the Allen County Purdue Extension Service. To send him a question, email [email protected]