Q&A: Why do my cucumber and zucchini plants wilt?

One Spotted and multiple Striped Cucumber Beetles, feeding on overripe pumpkin. Photo: Whitney Cranshaw, Colorado State University, Bugwood.org

Q: Last summer I had cucumbers and zucchini wilting and dying even though I’m pretty certain I didn’t have root rot or squash vine borer. What should I try this year so I can hopefully get a harvest?

A: Bacterial wilt disease, transmitted by cucumber beetles is the prime suspect for crop failure in this instance. Both of these garden pests – Striped Cucumber Beetle and Spotted Cucumber Beetle – are native to North America and can cause serious damage to vegetables in the squash/cucumber family, though they can also feed on unrelated fruits, vegetables, and ornamental plants.

Although their feeding causes direct plant damage, the main issue comes from their introduction of one or more plant pathogens. These beetles can transmit diseases like bacterial wilt and viruses, none of which are curable.

Delaying the planting of squash and cucumber transplants until mid-June may evade the host-seeking adults. Until they bloom, cover plants with insect netting or row cover (the former is ideal as it doesn’t trap heat). Bees will need to reach the flowers for pollination, but once the fruits start to develop, plants tend to be less susceptible to infection. Since more than one beetle generation can occur per year, clean-up veggie garden debris in autumn to deny remaining adults overwintering shelter.

For now, ‘County Fair’ is the only available variety resistant to bacterial wilt. This pickling cucumber is parthenocarpic– it produces mostly female flowers that don’t require pollination to set fruit. The Cucumber Beetles page at the Home & Garden Information Center has more information about these insects and their management.

By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun. Read more by Miri.

Send home gardening questions to Ask Extension at the Home & Garden Information Center

Semi-novice Gardener – Raised Bed Vegetable Garden Adventure (vol. 2)

I’m back with a big update on our raised bed vegetable garden efforts!  It’s been eventful: wildlife has eaten some of the plants, we built a whole new raised bed from scratch, and we’ve begun harvesting some of our first crops.

Tomatoes need support!

Our three tomato plants have been growing up well.  We procrastinated on adding support because I wanted a better solution than those flimsy conical wire doodads you can buy at the hardware store.  I eventually located some old lengths of wire fencing and just set them around each plant in a cylindrical shape and then attached them to a single metal garden stake to keep them steady.  I criss-crossed some twine back and forth which will give the tomatoes something more to grab onto and keep the support from bending outward.

Somebody is munching my plants!

Wildlife and insects have been having a feast on our garden, unfortunately. Continue reading

Climbing Cucumbers

Cucumbers stringed upGrowing produce in the backyard is a great way to experience fresher, new flavors that I oftentimes could not get from a store and give me a feeling of independence. In times of uncertainty, it is rewarding to grow even a small portion of food in the backyard.

I am a big fan of trellising vining crops in the vegetable garden. It saves garden space, saves my back from stooping over, and makes it easier to see the harvest instead of an impassable jungle! In previous years, I have used a range of materials from fencing and wire panels, but they can get rusty, hard to work with, and bent out of shape after a few seasons.

Last year, I tried a different approach. Using recycled 2x4s, I made a few fittings that perched snugly atop eight-foot steel t-posts. I drove the posts two and a half feet into the ground and spaced them about 10 feet apart. Through holes I drilled in the fittings, I ran two parallel horizontal wire tensile wires about 12 inches apart.

Fittings on post
These fittings were made from recycled 2x4s and decking screws.

Cucumbers clipped to strings
Cucumbers just after I clipped them onto the strings.

The wire was left over from some fencing work I’d done to try and keep the deer out. At each end, I anchored the horizontal wires to three-foot posts driven diagonally into the ground. Once the cucumbers were about a foot tall, I tied lengths of plastic tomato twine (one per vine) to the horizontal top wires. Using large tomato clips, I secured the cucumber vines to the vertical strings to train them up. When the vines were really growing, I had to check on them a couple times a week to simply retrain using more clips until they reached the top wire. At the end of the summer, I cut the vines down but left the lengths of twine up. The UV-resistant plastic looks like it has held up pretty well, and I plan to use it a second season.

Tomato clips on cucumbers
Large plastic tomato clips (25 mm) accommodate cucumbers and other vines and are available either online or from local produce supply companies.

On my trellis system, I grew the variety ‘Bristol’. It has a productive slicing cucumber with a broad disease-resistance package including tolerance to common cucurbit diseases like angular leaf spot, downy mildew, and powdery mildew. In 2019, my 30-foot double row yielded 10-25 pounds of cucumbers a week for about a month and a half before they finally succumbed to leaf diseases, cucumber beetles, and squash bugs. I was able to share the harvest with neighbors, friends, and family as well as can several batches of pickles that will last me until I start harvesting my 2020 cucumbers!

For small spaces or if you do not have wire and wood on hand, you also can grow cucumbers up a simple zigzag of plastic tomato twine between two steel t-posts. With a bit of tending and redirecting, the tendrils will climb their way up. As you plan your warm-season garden, I encourage gardeners to pair some type of trellis system with productive, disease-resistant varieties of cucumbers and other vining crops. Your back and your stomach will thank you. Happy gardening!

 

A simple trellis made with zigzag rows of plastic twine every 6-8 vertical inches.
A simple trellis made with zigzag rows of plastic twine every 6-8 vertical inches.

Luke Gustafson – Senior Agent Associate & Master Gardener Coordinator

Resisting Mosaic Viruses in Cucurbits

I grow most of my vegetables in a community garden plot: sunny, cheerful, with soil I’ve been improving with free compost for years now. It’s a good situation, but while community gardeners can share labor, tools, plants and seeds, they also end up sharing pests and diseases. Our garden has been suffering from a problem I never encountered at home or in the Derwood demo garden: mosaic virus on cucumbers and squash. Mostly I have dealt with this problem by the highly scientific method designated Not Even Trying, but this year I really want to succeed. So, some research!

Figure 1. Pumpkin plant infected with watermelon mosaic virus (WMV)
Photo by Dr. Gerald Brust of watermelon mosaic virus on pumpkin. Wait, what?

Continue reading

Squash Family Pest Problem Tips

CucumberThe squash plant family (Cucurbitaceae) includes many garden favorites- cucumber, summer and winter squash, pumpkin, muskmelon, and watermelon. Unfortunately, it’s a family vulnerable to some of the most consequential insect pest and disease problems. The names squash bug, cucumber beetle, squash vine borer, downy mildew, and bacterial wilt strike fear in a gardener’s heart. And those just represent the starting team. The legion of potential pest problems is sufficient to bring the toughest gardener to his knees sobbing in anguish.

But there’s hope for the human animals competing against insects, mites, and pathogens for these valued food resources. There are many ways to prevent and manage these problems and these are covered in detail on the HGIC website. Here are a few strategies that I think are less widely used. Give them a try in your pursuit of higher yields with fewer tears!

  1. Select disease resistant cultivars. Cornell University’s Vegetable MD Online website has a matrix for each vegetable crop that lists all major diseases and cultivars with resistance claims. They even include seed companies that sell the seeds! Special note: ‘County Fair’ cucumber is resistant to bacterial wilt; butternut and ‘Tromboncino’ squash are fairly resistant to squash vine borer.
  2. Apply floating row covers when seedlings emerge or transplants go in. The material excludes all critters. Remove the cover when plants start to bloom.
  3. Plant around insect pests by planting healthy transplants as soon as conditions allow or waiting until mid-June to plant seeds. Plant pumpkin and winter squash from late June to July 4th.
  4. Keep planting. Cucumber and summer squash can be sown several times, 2-3 weeks apart.
  5. Scout your plants for signs and symptoms of problems and take action early!

Continue reading