By Denise Seghesio Levine, UC Master Gardener of Napa County
Most of us have warm, fuzzy feelings about ladybugs. We feel special when a ladybug lands on our hand. We charm our children with early garden experiences and recite iconic nursery rhymes as we entreat the cheerful red beetles to “fly away home.”
Ladybugs, or lady beetles, with their shiny red shells and black dots are friends in the garden, helping to eradicate aphids and other unwanted pests.
But what about the yellow-green version? You may have noticed chartreuse, shiny-shelled “ladybugs” with 11 or 12 shiny black spots as well. The yellow versions do have longer antennae than the red versions, but so what? Are they yellow ladybugs?
These yellow-green beetles are actually cucumber beetles, Diabrotica undecimpunctata. Unlike friendly ladybugs, cucumber beetles can wreak havoc in your garden and are hard to get rid of.
Adults cause the most damage.
If you are finding large holes in the foliage of your beans, cucumber, melons, squash, corn, potatoes, tomatoes, eggplant, beans, peas, beets, asparagus, cabbage, lettuce and other vegetables, look for these little pests on top of and under leaves.
Just about all the stone fruits are also susceptible to cucumber beetles, including peaches, apricots and plums. Shoots and blossoms of peas and beans, cucumbers and melons are not safe from attack either. I do not think they eat onions.
And this really points to the problem with trying to get rid of this voracious pest. Rotating crops (not planting the same crop in the same space for a few rotations) is one of the few effective ways to control Diabrotica undecimpunctata, but how do you rotate crops effectively when cucumber beetles eat almost everything?
Cucumber beetles are about ¼ inch long with a black head. Their larvae are whitish and slender although the head and tip are slightly darker. They sport three pairs of short legs and feed exclusively on roots as they develop. They like roots of corn, beans, wild grasses, small grains and sweet peas. They can overwinter in beds where they ate your crops the previous year or move out to the weedy outskirts.
Normally at this stage Diabrotica undecimpunctata do little damage, and most plants can survive. It is when the larvae mature and your plants begin to grow and leaf out, or your next batch of seeds start to germinate and push up, that the real onslaught begins.
Newly emerged seedlings are most susceptible and can be destroyed in a few days. Once plants get large enough, they might look terrible with munched leaves and damaged fruit, but they will usually survive.
It happens like this. Beetles overwinter in your garden and surroundings. When your spring plantings begin to emerge, adults begin laying their yellow-orange eggs at the roots. Tucked in cracks in the soil and at the base of plants, eggs are invisible to all but the most diligent examiner.
When the larvae hatch, they spend their first two to six weeks eating the roots of your plants. They emerge as adults about the same time your vegetables begin leafing out. Then they begin feeding on foliage, seedlings and small plants. They can reproduce and go through this cycle up to three times each year.
So what can you do if you find these culprits in your garden? If you do have room to rotate your crops, do it. And clean the weedy outskirts of your garden so they do not have places to overwinter.
There really are no recommended insecticides. They would need to be applied too often to be effective. Botanical controls, while safer, tend to be especially short-lived in efficacy.
A better strategy is to use protective cloths or screens over your newly sown seed or just-planted transplants, removing the protection only when the plants are large enough to sustain damage or begin to flower. Removing barrier cloth at flowering is essential to allow beneficial insects to pollinate.
There is some ongoing research on the effectiveness of natural predators, but not much conclusion on the efficacy. Since cucumber beetles are attracted to cucurbitacins, some experiments have used lures containing cucurbitacin powder. The method has been effective, but there are no current plans to move ahead with such a product commercially. My own preferred technique is more rudimentary. Remember, these insects are not your friends. When I see yellow “ladybugs” on my plants, I squish them.
Next workshop: “Home Vineyard: Part 2” on Saturday, September 14, from 9:30 to 2:00 p.m., in Calistoga. Learn techniques to maintain your new or existing home vineyard. Workshop location will be provided after registration. For more details & online Registration go to http://napamg.ucanr.edu or call 707-253-4221
The UC Master Gardeners are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website (http://napamg.ucanr.edu) or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.
The back of my property has a utility easement that prevents me from fencing my yard. Consequently, I spent several years experimenting with remedies for keeping deer out of my garden. I finally acknowledged that there is no substitute for a fence.
To allow utility access but still repel deer, I chose heavy-grade synthetic mesh netting that wouldn’t degrade in sunlight or extreme temperatures. For a few years, the netting worked. But this year, I learned a lesson. It’s not enough to put up a fence. You have to inspect it occasionally for holes or breachable openings. And you have to latch the gate, not just close it.
Otherwise, you may walk into your garden one day, as I did, and discover a downed fence and ravaged plants indicating that deer and other critters had come for brunch. While synthetic fencing is durable, falling tree branches can take it down and skunks can chew through it.
Last year also taught me a strawberry lesson. For a few seasons, we have enjoyed strawberries planted from nursery six-packs. Last year we planted bare-root strawberries. I tried to follow the instructions meticulously. I prepped the soil, soaked the plants before planting and planted the starts at the specified depth. A few weeks later we had a heavy rain. I thought nothing of it at the time. But when I checked on the plants a few days later, they were all gone, apparently uprooted and washed away. Not planted deep enough, I guess.
Kohlrabi is a root vegetable used in hearty soups and stews. I grew three varieties from seed last year, germinating the seeds in biodegradable peat pots that I could bury in the ground when the seedlings grew large enough. I set the trays of pots in the sun and waited for the seeds to germinate. Two days later, I discovered that two of the trays had been tipped over, and many of the pots had been trampled or crushed. I suspect raccoons, but it might have been skunks. The only way to know for sure was to replant and set up a motion-activated camera to catch the miscreants. I replanted the two trays and set them out again without surveillance.
The seed trays went undisturbed for weeks, and most of the seeds germinated. The seedlings survived a stay at a family member’s house while I went on vacation. Then one day I went out to check on the plants and discovered that three-quarters were missing. The pots were still there but the plants had been eaten, stalks and all.
The next day, at the farmers’ market I saw a six-pack of kohlrabi. I decided to try one more time, hoping that these seedlings might be less appetizing. I also had some leftover seed which I sowed directly in the ground. When I checked a few days later, all of the plants were gone, and none of the seeds had germinated. I finally gave up on kohlrabi and planted onions and garlic in this space.
I should acknowledge that my wife had suggested that I use a row cover to protect the seeds and young seedlings. But I am a Master Gardener, so I know better than she does. One lesson learned is that row covers are a good idea when starting plants from seed. Another lesson is that my wife is smart.
After discussing me experience with other Master Gardeners, I’m convinced that the neighborhood quail flock demolished my kohlrabi. Apparently, quail enjoy plants in the brassica family, including kohlrabi, broccoli, kale, cauliflower and brussels sprouts.
Last year something also ate my tomatoes and lemons. I have seen birds eating tomatoes before, but the lemon damage surprised me.
One night, when I went out to the garden with a flashlight to get some tomatoes for dinner, I saw something move. I turned and pointed my flashlight on a skunk checking out the tomatoes. I have never before been face to face with a skunk. Assuming it was going to spray me, I sprinted for the back door. I decided that skunks can have the run of the garden at night as long as they leave me some vegetables to harvest during the day.
As you can see, it was an eventful year in my garden. I harvested a variety of vegetables, some fruit and flowers, and I learned more about coexisting peacefully with the creatures who also like my yard.
Public Workshops: Napa County Master Gardeners are leading a workshop on “Warm Season Veggies” on Saturday, March 9, from 9:30 a.m. to 11:30 a.m. Prepare now for your most successful vegetable garden ever. Learn what to plant from seed, how to choose transplants, and when to plant for a bountiful harvest from spring into fall. The workshop will be held at the University of California Cooperative Extension office (address below).
Join Napa County Master Gardeners on Saturday, March 16, from 9:30 a.m. to 11:30 a.m. for a hand-son “Tool Time” workshop. Learn how to recondition and rejuvenate your old garden hand tools. Get advice on selecting new garden tools and tips on proper and safe use. Location: Connolly Ranch Demonstration Garden, 3141 Browns Valley Road, Napa.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners (http://cenapa.ucdavis.edu) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions?