What's Behind These Cucumber Complications?
Helpful Products from Gardens Alive!
Garden Army Multi-Purpose Nematodes
Floating Row Covers
The Dripster™ Irrigation Kit
Gardener's Gold™ Premium Bagged Compost
A. I would not call this 'success', Jules. With success, you get cucumbers. With failure, you get eggroll. Very old eggroll; and no duck sauce.
Unless you've actually seen them, we can rule out cucumber beetles, as the adults are a good size (around a quarter inch long) and appear during the day. You can't miss 'em. Striped cuke beetles are the most common form of this pest and feed only on cukes and other members of the cucurbit family (squash, pumpkins, etc.). Spotted cuke beetles are more common down South, attack a wide variety of plants and show up much later in the season in the North.
Both beetles have similar life cycles. Adults emerge from leaf litter in the Spring and females lay eggs in the soil around newly installed cucumber plants. After the eggs hatch, larvae emerge and chow down unseen on the roots of the plants. Then they transform into adults who feed on the upside of the plants. In addition to all this physical destruction, they transmit bacterial wilt, a typically fatal disease (the plants should be quickly destroyed) and Squash Mosaic Virus, which causes the fruits to look ugly and unappetizing.
Beneficial nematodes are a great strategy for prevention, as these microscopic predators will seek out the little larvae and destroy them before they can become adults. Other preventative advice is to only install good size plants; don't rush the season! Floating row covers are also advised once you spot the first adults of the season. For more info, read our previous articles on these pests and an informative Wisconsin Dept of Agriculture Bulletin that we'll link up to: https://hort.extension.wisc.edu/articles/cucumber-beetles/
But we are almost certainly dealing with disease here! Specifically a mildew, but not powdery mildew. This disease of warm, humid and crowded conditions, as its name suggests, presents as a white powder on the leaves. It typically does not kill the plants but can reduce the harvest, and it looks like Holy Heck in your garden. Crowding is a major cause, so be sure your plants have room for air circulation between them. You'll get more cukes from two plants spaced well apart than from four that you planted too close together.
Powdery mildew does not linger in the soil; it is delivered from nearby infected plants by the wind every season. So if your neighbor is ignoring their powdered plants, yell: "What?! I shouldn't get any pickles because of you?!"
This disease has the most of those popular 'kitchen sink cures' that have been verified effective, including dilute solutions of whole milk, and baking soda plus oil preparations. Lots more cool stuff about this at Wiki.
Alright Kats and Kittens, if you're keeping track at home, the score is two down with one player remaining: Downy Mildew; the only plant disease linked to overuse of a chemically scented fabric softener.
Ahem. I make joke.
Downy mildew is one of a number of similar pathogens grouped under the category "water molds", and these are nasty creatures. I'm pretty sure this is what's afflicting our listener, as the first visible symptoms are 'chlorotic' spots on the leaves, appearing yellow to green at first, then progressing to bright yellow and then brown and distorted. The condition is, of course, "poorly understood" but plants that are placed out too early in the season suffer the most, as do plants that are crowded.
A very interesting website called "Plantophiles" adds the observation that mites, whitefly and aphids can all infect cucumber plants with mosaic virus, so keep checking both sides of your leaves to see if you can catch sight of one of these little buggers.
Bullet point time:
Cucumbers are probably the worst plant to put out early in the Spring via seed OR plants. Best to wait until the weather warms up.
Plant in full sun, with more room between plants than you think you need.
Plant in naturally compost-rich soil. Explosive chemical fertilizers like Miracle-Gro, Peter's and Osmocote force excessive growth that is very attractive to insects that carry disease.
Rotate your crops. Never plant cukes that have had problems in the same spot the following season. Researchers seem to agree that a rotation with sunflowers depresses disease problems.
Never wet the leaves when you water. Let a hose drip gently at the base of your plants or use drip irrigation. Water in the morning only.
Don't let your growing plants lie (or lay) on the ground; trellis them upward to keep the fruits off the ground and their leaves dry.
Remove diseased leaves promptly.
Resistant varieties are available for all these issues. Research your symptoms carefully and choose a variety whose resistance matches your problem.