Controlling Japanese Beetles, Roses for Everyone!

More info about Episode 133 of the Garden Basics Podcast, released Aug. 31, 2021

Photo: Raymond Cloyd, KSU

Listen to Episode 133 of the Garden Basics with Farmer Fred Podcast for more information about Japanese Beetle control, excellent roses for everyone, the oxblood lily, and more.

The takeaways from our discussion about Japanese Beetle control with Master Rosarian Debbie Arrington from the Sacramento Digs Gardening newsletter:

• The most effective treatment available to the home gardener is hand-picking and squashing or drowning these pests. Simply fill a container, such as a coffee can, with soapy water, and flick off the beetles into the can. Later cover it and dispose of them. The process is easy because the beetles move very slowly and do not hide, and early efforts pay off with a much reduced population. (Cornell University)

• Controlling the Japanese Beetle grub population in your lawn is key. Among the controls available:

1. Insect-eating nematodes—microscopic parasitic roundworms—actively seek out grubs in the soil. (Amazon: Nematodes for Japanese Beetles Control) These nematodes have a mutualistic symbiotic relationship with a single species of bacteria. Upon penetrating a grub, the nematode inoculates it with the bacteria. The bacteria reproduce quickly, feeding on the grub tissue. The nematode then feeds on this bacteria and progresses through its own life cycle, reproducing and ultimately killing the grub. The two nematodes that are most effective against Japanese beetle grubs are Steinernema glaseri and Heterorhabditis bacteriophora. (USDA: The Japanese Beetle Control Handbook)

2. A low toxic soil drench containing the active ingredient Chlorantraniliprole (found in Grub Ex, (a Japanese Beetle Grub control for turf that only works on future outbreaks of grubs). Although that active ingredient is not considered organic, Michigan State University says that Chlorantraniliprole is not toxic to bees, unlike other grub control products. Click on that Michigan State link for more information about the timing and use of grub control products.

3. Japanese beetle larvae feed on roots of grasses, in a manner similar to other turf damaging white grubs.These injuries produce root pruning that limit the plant’s ability to acquire water. Damaged areas of turfgrass are more susceptible to water stresses and severely pruned roots can lead to plant death by drought. It is likely that there will be increasing turfgrass damage in areas where this species becomes established, adding to the damage done by native white grubs (Colorado State University)

   On happier notes in Episode 133 of Garden Basics: Roses For Everyone, and Outstanding Bulbs!

   The fun part about interviewing gardening experts is getting those extra tidbits that are so useful! For example, Master Rosarian Debbie Arrington was on Episode 133 to talk about Japanese beetle control. But since I had her attention, why not ask….

Knockout Roses and Drift Roses featured on Amazon.

Also on Episode 133, we talked with the Superintendent Emeritus of the UC Davis Arboretum and Public Garden, Warren Roberts, about the Plant of the Week…this beauty right here…with the gruesome name, Oxblood Lily, (Rhodophiala bifida). This late summer-early fall blooming bulb does well throughout most of the Sunbelt (USDA Zones 7-10), but can be grown in containers and brought in for the winter in colder climates.

And, as an aside, Warren mentioned a book that he highly recommends for bulb enthusiasts: "Garden Bulbs for the South," by Scott Ogden

Don’t Confuse Japanese Beetles with the Green Fruit Beetle

They're Big, Loud and Hungry: The Green Fruit Beetles are Buzzing Throughout California and the West

     While searching for ripened tomatoes in the garden last night, a familiar loud buzz zoomed by my ear. You may be hearing that same ferocious buzzing as you are picking the backyard tomatoes, figs, corn and berries these days. You just might be disturbing the eating habits of the green fruit beetle (Cotinis mutabilis), munching away at the overripe and damaged fruits and vegetables in your garden. It's not just the sound that will stop you in your tracks. The combination of the biplane-like buzz as well as the sight of these slow flying, large (an inch and a quarter long), metallic green-shelled creatures might make you drop your crops.

And yes, here in California, add the green fruit beetle to the list of suspects when you notice a chomped-on tomato.

Entomologist Baldo Villegas of the California Department of Food and Agriculture says his office has noted the growing presence of green fruit beetles in southern Sacramento County, beginning a few years ago. Until the 1990's, they had only migrated as far north as Fresno.

"This beetle is now widespread from Mexico to the southwest and into northern California," says Villegas. "They are migrating northward fast." Villegas explains that the beetle is more vexing for backyard gardeners than commercial growers. "I consider them a nuisance pest," says Villegas. "They feed on rotting or open fruit and are attracted to them by the gas emitted by the fruit."

A native of Mexico, Villegas recalls the green fruit beetle as a harbinger of summer. "We used to catch them on fruit damaged by birds or in rotting fruit laying around on the ground," says Villegas. "We would tie a piece of string on one of their hind legs and that would allow them to fly along side of us."

Unlike a balloon on a string that escapes your grasp, the green fruit beetle is not going to drift away, high into the sky. Right now, those beetles are laying their eggs in your piles of garden compost, manure and mulch. So, the best control is to remove any such piles from the areas where you have seen the feeding adults. Turning the piles frequently will expose the larval stage of these beetles, a C-shaped, creamy white grub. Hand picking or flooding the area for two days can limit these noisy munchers during the next gardening season. And, chickens consider those grubs a delicacy.

To limit the spread of the adult beetles now, take away their food supply: fruit that is getting too soft on the vine. Trapping might be somewhat successful, according to UC Davis Integrated Pest Management Director Mary Louise Flint. In her book, "Pests of the Garden and Small Farm," she says that the green fruit beetle can be attracted to a half-filled one gallon jar, containing a 50-50 mix of peach or grape juice and water. Make a funnel out of small mesh wire and place it in the jar's opening. This will allow the beetles to get inside, but not back out. 

Insecticides are not recommended against the adult green fruit beetle. The UC Davis Integrated Pest Management website offers these tips for green fruit beetle control: "Early harvest and removal of fallen fruit can also reduce damage. To manage grubs (pictured here), remove all manure, lawn clippings, or leaf piles from areas near fruit trees and turn compost piles frequently to speed decomposition and expose small grubs. If grubs are found, they may be killed by flooding the infested area for at least 2 days."

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