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.
![Here's a cucumber beetle (UC ANR) Here's a cucumber beetle (UC ANR)](/blogs/blogcore/blogfiles/62247.jpg)
![Lady beetle, aka ladybug (UC ANR) Lady beetle, aka ladybug (UC ANR)](/blogs/blogcore/blogfiles/62245.jpg)
![Lady beetles come in spotted and spotless versions. (UC ANR) Lady beetles come in spotted and spotless versions. (UC ANR)](/blogs/blogcore/blogfiles/62246.jpg)
![And here's a cucumber beetle having lunch--or maybe dinner (UC ANR) And here's a cucumber beetle having lunch--or maybe dinner (UC ANR)](/blogs/blogcore/blogfiles/62248.jpg)
Few other vegetables are more representative of fall than pumpkins. Come October, mounds of pumpkins of various shapes and sizes are a common sight in Napa Valley. While they may seem to suddenly appear, pumpkins have a fairly long growing season. If you are considering growing pumpkins in your garden for a fall harvest, it's time to plant.
Pumpkins belong to a large botanical family that includes melons, cucumbers and other squash. Some tiny pumpkin varieties can fit in the palm of your hand. The record-setting types weigh in at over a ton. Pumpkins also come in shades beyond jack-o-lantern orange. For an unusual addition to your garden, seek out white, red or blue-skinned varieties.
One bonus of planting pumpkins is that they attract bees. Honeybees will happily do the work of pollination, but a garden with a range of plants will lure and nurture other bee species. Squash bees tend to fly early in the morning, before honeybees get going. You may never even know that they have visited your garden. To encourage squash bees, consider adopting a no-till regimen. Squash bees nest several inches below the soil, and frequent tilling can destroy their habitat and nesting populations.
It is a joy to watch pumpkins grow, but they do need space. If your garden has ample room, allowing the plants to ramble can help shade and cool the surrounding soil and prevent weeds from growing. Before planting, amend the soil with compost to get plants off to a healthy start. Plants can be started in small pots or direct-seeded. If you are aiming for maximum size, feed with a high-nitrogen fertilizer to stimulate leaf growth. When blooms appear and fruit set occurs, phosphorus and potassium become more important.
Once established, pumpkins grow fast. To promote larger pumpkins, select one or two good specimens and remove all others on the vine. This pruning will help the plant transfer nutrients to the remaining units.
Squash leaves can be susceptible to mildew. Irrigating with drip or soaker hose is preferable to overhead watering. Remove diseased leaves as soon as possible and do not overwater. Leaves may wilt on hot days but typically recover as the weather cools. If wilting persists, check to make sure plants have adequate water
Common pumpkin pests include cucumber beetles and vine borers. A home gardener can tolerate some damage rather than resorting to chemical sprays. Remember that pollinators and other beneficial insects might be frequenting the plant, too. Use light-permeable row covers to protect plants if an infestation is particularly heavy.
Trap crops can also help reduce insect damage by providing an alternative food source. Crop rotation can help by eliminating available food sources for future generations of pests. The University of California's Integrated Pest Management database is an excellent resource for pest- and disease-control advice.
Besides being delicious, pumpkins have other advantages for the home gardener. They can help minimize weed growth around taller plants such as sunflowers. Native Americans understood the wisdom of planting pumpkins with beans; the beans add nitrogen to the soil and pumpkins are heavy feeders. Many pumpkins store well and can provide tasty meals in winter when many vegetables are out of season.
You don't have to wait for the pumpkin to mature before enjoying the plant. The leaves are edible and can be cooked like spinach. Choose young, tender leaves for that purpose. Of course, the seeds are edible, too. Enjoy them roasted and salted to increase the food value of your crop, particularly if you have limited space. Saving seeds and swapping with friends can increase your garden's diversity with no extra expense.
Pumpkins grow well in Napa Valley. Consider planting a beautiful heirloom cultivar to enjoy as a table centerpiece in winter. Between the pumpkin's tasty flesh, its seeds and its nutritious leaves, this plant hits a triple.
Workshop: U.C. Master Gardeners of Napa County will hold a workshop on “Succulent Plant Success” on Saturday, July 7, from 9:30 a.m. to 11:30 a.m., at University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Bring your love of succulents to this workshop dedicated to helping succulent gardeners grow the show-stopping plants we all hope for. Master Gardeners will show you the right kind of soil and containers and how to care for your succulents. They will also discuss myriad succulent types to help you make a succulent garden for yourself or to give as a gift. Please bring succulent cuttings you would like to share.Online registration (credit card only); Mail-in/Walk-in registration (check only or drop off cash payment).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) 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? Find us on Facebook under UC Master Gardeners of Napa County.
Help for the Home Gardener from the Contra Costa Master Gardeners' Help Desk
chewing on a leaf
Reply from the CCMG Help Desk: The insect you brought to share with us is indeed a garden problem. It is a Western Spotted Cucumber Beetle (Diabrotica undecimpunctata). The adults of this beetle feed on the leaves of melons, squash and other cucurbits, as well as corn, potatoes, tomatoes, eggplant, beans, peas, beets, asparagus, cabbage, lettuce, and other vegetables...almost all the popular vegetables. They also feed on ripening peaches and apricots and other soft fruit. Management of this pest can be difficult if not caught early on. Small seedlings can be destroyed quickly; however, established plants are more likely to survive an attack.
The least toxic method of extermination is hand picking and dropping into a bucket of soapy water to drown them. Since the beetles are now attacking your Calendulas, you may want to remove or cut the plants down and bag the remains for disposal in your garbage in order to get rid of any potential eggs or larvae that may be on them. This should help reduce the population of the beetle in your garden.
Young seedlings and other small plants can be protected from damage by coverings such as screens, protective cloth, or individual cups or cones until they are large enough to tolerate damage.
Here is a link to some more information on this pest, along with pictures to help you with identification: ttp://www.ipm.ucdavis.edu/PMG/GARDEN/VEGES/PESTS/cucumberbeet.html
Good luck managing these destructive insects! Fortunately you covered your vegetables before the beetles moved in to your garden! Keep your protection in place. You probably should keep the covers until plants are at leasatlarge enough to withstand damage from the beetles.
Contra Costa Master Gardeners Help Desk
Note: The Contra Costa Master Gardener Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/
- Author: Kathy Keatley Garvey
If it looks like a duck, swims like a duck and quacks like a duck, then it probably is a duck.
That inductive reasoning (known as "the duck test") doesn't hold true for yellow bugs with black spots.
A yellow ladybug (ladybird beetle) and a cucumber beetle look a little alike--at first glance. They're both yellow. They both have black spots.
But they're worlds apart. One is a beneficial insect. The other is a pest.
We spotted a spotted cucumber beetle (family Cerambycidae) on our sunflower plant last summer. It's a common insect in California. It eats all kinds of flowers and leaves. It's often seen on plants in the squash family. Figures. We had a squash plant in our garden. (Notice the "had.")
Ladybugs (family Coccinellidae) aren't always the classic reddish-orange color and they don't always have spots. They can be mellow yellow! But they're your buddies. They feast on aphids, mealybugs, mites, and other soft-bodied insects.
I figure that between these two insects, the ladybugs are the bright spots in the garden.
![A yellow ladybug on sage. The ladybug (ladybird beetle) is a beneficial insect. (Photo by Kathy Keatley Garvey) A yellow ladybug on sage. The ladybug (ladybird beetle) is a beneficial insect. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/897.jpg)
![The spotted cucumber beetle is a pest. It's often seen on plants in the squash family. (Photo by Kathy Keatley Garvey) The spotted cucumber beetle is a pest. It's often seen on plants in the squash family. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/900.jpg)