Knowledgebase
Does anyone know what is killing cucumber plants in Saginaw County #765290
Asked August 02, 2021, 3:24 PM EDT
Saginaw County Michigan
Expert Response
Is it possible to attach 2-3 pictures of examples? A close up of a wilted stem, with leaves attached, that has just wilted; and an overall picture of whole plant(s) ?
This would be very helpful to our vegetable expert. Thank you.
I have been bagging dead plants and plan to burn them later. Then I need to plan what to try to prevent this from staying in the soil over the winter. Literally hundreds of hours of work by me and other folks has been destroyed already with no idea what to do to halt this destruction. Any help would be appreciated and I will share any with a lot of others.
John Hildebrand
The cucumbers have downy mildew. This pathogen arrives here every year in July and kills cucumber plants. To avoid it for as long as possible, plant as early as you can to maximize harvests, avoid overhead watering, spray with chlorothalonil preventively starting in July. But, heavy downy mildew pressure in the community late in August and September will overcome chlorothalonil. A variety with proven resistance to downy mildew right now is DMR 401.
The zucchini is a mystery without additional information. It would be useful to see the base of the stem, the roots, and any fruits that touch the ground.
There are about six common sources of wilts in vine crops, with four of them covered in this list from Penn State. Fusarium, and Verticillium can be identified by cutting the stem within 10 inches of the ground and looking for brown discoloration inside the stem. The roots will be healthy.
Bacterial wilt, and cucurbit yellow vine decline are diseases that are transferred by cucumber beetles, and squash bugs, respectively. They can only be managed by managing the insects. The picture you sent does not look like yellow vine decline. One other insect-driven wilt is from the squash vine borer caterpillar, which hatches from eggs laid at the base of the plant and then burrows into the stem. You can easily check for this by looking for a hole at the base of the plant with wet "sawdust" coming out of it. The caterpillar is all white, and may have already left to pupate in the soil if you can't find it.
The only big wilt causing thing missing from the Penn State list is Phytophthora, which is a soil pathogen that can attack the root, crown, shoots, leaves and fruits in an all out assault after rainy periods. Fruit are easy to diagnose with a yeasty white mat of spores on the infected part. This is managed with raised beds and sanitation. Never keep Phytophthora plants around once they are diagnosed. Destroy them promptly or remove if possible. Do not add to compost piles. Avoid planting cucurbits, legumes, and solanaceous crops in the same place year after year. They can all get it and keep the population going.
