- Author: Kathy Keatley Garvey
So there you are, admiring your Coreopsis and suddenly you notice spots and holes--spots on the backs of two western spotted cucumber beetles, and holes cut in the petals.
Ah, there's two of them.
The beetles, about a fourth of an inch long, are fun to photograph, but they're not your buddies. Nor would they want to be!
"Cucumber beetles are very common pests in vegetable gardens and may also attack ripening stone fruit," says the UC Statewide Integrated Pest Management Program. "The most abundant species in California is the western spotted cucumber beetle, Diabrotica undecimpunctata...The western spotted cucumber beetle is greenish yellow and has twelve black spots on its back."
Ever counted the spots? Yes, 12.
We've seen the beetles feeding on the leaves of flowers and many vegetables. "Cucumber beetles may also spread cucumber mosaic virus or wilts in cucurbits," UC IPM says. "Larvae feed exclusively on roots, but do not generally damage garden plants, although corn may occasionally be damaged."
Spotted cucumber beetles don't move very fast early in the morning, so they're fairly easy to photograph.
And sometimes you get a "two-fer," two in the same image. 24 spots.
- Author: Kamille Hammerstrom
Last weekend I went out to my back porch to water and deadhead my container garden and came across some damage to my cosmos. The petals of most of the flowers had multiple small holes. I looked more carefully and noticed that the tomato plant next to the cosmos also had small holes in the leaves and in the fruit. Now I was curious! What was causing this damage to my plants? As I started turning over leaves and rotating tomato fruits, I spotted what looked like a yellow ladybug. A-ha! A potential pest! But who was this spotted critter?
As is indicated in the common name, Western spotted cucumber beetles and cucumber beetles in general are common on cucurbits, that is melons and cucumbers. But they also will feed on other tender succulent portions of garden plants, including the flowers and leaves. The life cycle includes several generations a year, with eggs laid at the base of plants or in soil cracks, larvae which burrow into the soil and eat plant roots, and adult beetles that attack the aboveground portions of plants. Adult beetles are shiny with black heads, long antennae, and yellowish bodies with black spots. There's also a related striped cucumber beetle that has stripes rather than spots, but does pretty similar damage in the garden.
For more information, check out the UCANR Integrated Pest Management information here and here. Don't forget to subscribe to our blog so that you receive an email notification when a new post goes up. If you have questions, contact us online, by phone or in person to get answers to your gardening quandaries!
- Author: Kathy Keatley Garvey
How many times have you heard that?
Often it is not the beneficial lady beetle--commonly referred to as a ladybug--but that dratted pest, the spotted cucumber beetle.
In a case last week, it was the dratted spotted cucumber beetle, or more specifically, the western spotted cucumber beetle, Diabrotica undecimpunctata undecimpunctata, being "diabotical" on an Iceland poppy.
Lady beetles, the good guys and girls, can be many other colors besides red with black spots. They can also be with or without spots or stripes. They're the blue ribbon winners when it comes to devouring aphids and other soft-bodied insects.
The spotted cucumber beetle, however, is a pest of many of our agricultural crops, including the cucurbits family, Cucurbitaceae, which includes cucumbers, squash and zucchini. You'll also find these little diabolical munchkins just about everywhere.
"Western striped cucumber beetle larvae feed exclusively on cucurbit roots, whereas western spotted cucumber beetle larvae feed on a wide variety of plants including grasses, corn, legumes, and cucurbits," according to an entry in the UC Statewide Integrated Pest Management (UC IPM) Program's Pest Management Guidelines.
So, the next time you're slicing a melon, remember what UC IPM says: "Cucumber beetles are serious pests of smooth-skinned cucurbits, especially melon varieties such as honeydew, crenshaw, and casaba. While the adults prefer tender, succulent portions of plants, including the flowers and leaves, which they may destroy with their feeding, it is the damage to the surface of the melon that reduces marketable yield. When temperatures are high, adults especially feed on the undersides of young melons, scarring them. After the skin hardens, melons are much less subject to attack. Scarring in the crown of the plant is also typical of adult damage. Feeding on stems of young plants, followed by sustained winds, may result in severe stand reductions making replanting necessary. In some situations, larvae may cause serious injury by feeding on roots, and young plants can be killed. Cucumber beetles also spread squash mosaic virus."
A cute little ladybug? No.
Pretty? Well, it is quite photogenic.
- Author: Launa Herrmann
My genealogical roots deep run through many a corn field since I was born from a Nebraska-farm girl mother and an Indiana-raised father. Field corn. Popcorn. Sweet corn. You name the corn, my relatives planted it. Several decades back I even grew ornamental corn one summer to decorate Christmas wreaths. So needless to say I was riveted to a recent Wall Street Journal article about how Mother Nature is outsmarting genetically modified corn seed. (Ian Berry, “Pesticides Make a Comeback”, Wall Street Journal, May 22, 2013, p. B-1.)
Seems that entomologists at the University of Illinois and Iowa State University found corn rootworms immune to Monsanto’s Bt (Bacillus thuringiensis) gene. That gene was originally designed to shield corn crops from this pest that feeds on leaves, tassels and silks; injures roots and can stunt or kill young shoots and plants.
The article also points out that last year America’s farmers planted 97 million acres in corn based on increasing prices and EPA approval touting reduced insecticide use that would give growers and farm workers “greater safety, protect water bodies from runoff and mitigate” harm to wildlife.
“Some of those gains are quickly being reversed,” said Michael Gray, a UI entomologist quoted in the story, who went on to say that next year over a quarter of corn farms plan to use insecticides as “cheap insurance.”
Makes senses now why sales are up for pesticide producers. To read the entire article, log on to WSJ online or review a similar story “Pesticides make a comeback against Monsanto seed” at
http://www.bignewsnetwork.com/index.php/sid/214688991/scat/3de2685784ae51b
Frankly, I wanted to know exactly what this crawly critter chomping on corn crops looked like. During my research of “corn rootworms,” I discovered crop damage is not limited to larvae but includes the adult — two familiar beetles often found in our own backyard vegetable patch that also feeds on cucurbits, legumes and grasses — the Western striped cucumber beetle (Acalymma trivittatum) and the Western spotted cucumber beetle (Diabrotica undecimpunctata undecimpunctata). (See UC IPM Pest Management Guidelines: Corn, plus UC ANR Publication 3443. Also UC IPM Pest Management Guidelines: Curcurbits, plus UC ANR Publication 3445.)
Photos below are of the Western striped cucumber beetle and the Western spotted cucumber beetle).
And there’s more. In fact, there’s also a banded cucumber beetle (Diabrotica balteata) and a spotted cucumber beetle (Diabrotica undecimpunctata howardi), also known as the Southern corn rootworm. In addition, there’s the Northern corn rootworm (Diabrotica barberi Smith & Lawrence), and the Western corn rootworm (Diabrotica virgifera virgifera LeConte).
When you compare the above two photos with photographs on Purdue University’s IPM website, you’ll notice that our Western spotted cucumber beetle looks identical to the Southern corn rootworm and that our Western stripped cucumber beetle appears the same or similar to the female Western corn rootworm. Plus, there’s a photo of the larvae -- the actual rootworm. Here’s the Purdue IPM link:
http://extension.entm.purdue.edu/fieldcropsipm/insects/corn-rootworms.php