Beetlemania

by Bob Shaw, EMGV

Japanese beetles have emerged in Durham County. We have been picking them from our orchard trees at Briggs Avenue Community Garden since the start of June. This time of year takes me back 40 years to our first house out in Orange County sitting in a large yard, but surrounded by woods. On an early June morning, as the sun warmed the ground, I watched in dismay as clouds of beetles rose from the turf. For the next years, I warred against them — inoculating my lawn with milky spore bacteria (then available only from the county extension agent) and with traps. More about traps later. Each afternoon, I’d come home from work and empty a full gallon of beetles from my traps into a bucket of soapy water. Over the years, I accumulated a large pile (not quite a mountain) of beetle husks. Eventually, I controlled them and my apple trees no longer had all their leaves turned to brown lacework, no longer were my peaches gnawed to brown, nasty pulp.

Japanese beetles on an apple tree.
Photo by Bob Shaw


At Briggs, we don’t have a plague and we manage them with an old plastic container of soapy water. In the cool morning, when they are still lethargic, one holds the container beneath the beetles’ leaf and, obligingly, they drop into it; this works best at 70 degrees or lower. As the temperature rises they are more active and are likely to fly as you approach. Collecting one is very satisfying, even more when a pair is caught in flagrante delicto or, even three or more, when onlookers are present.

We find beetles on, and eating leaves of, roses, apples, peaches and persimmons in the community garden. A few beetles are on our figs, but they haven’t eaten the leaves. Likely the broad, flat, green leaves provide a nice landing zone. But as the population grows, they range more widely: into mint and blackberries.

About traps:  As described above, I used them many years ago and traps saved us. If beetles are a plague, as they were with me, collection in cups of soapy water may not seem practical. However, be aware that beetles must be emptied from the traps every day or two to prevent them from rotting and releasing ammonia which is repellent to other Japanese beetles. Traps also can attract beetles from your neighbor’s yard, increasing the population in your yard. So what? – We want to be good neighbors, don’t we?

Sources & Further Reading

https://content.ces.ncsu.edu/japanese-beetle-1

Coping During Japanese Beetle Season

Coping During Japanese Beetle “Season”

by Kathryn Hamilton, EMGV

At this time of year, Japanese Beetle “Season,” my favorite gardening tool

P1000072
Beetles are most sluggish in early morning.

is a plastic fork.

When disrupted, beetles are supposed to fold their hind legs and fall. You are supposed to be able catch them with a container of soapy water. In my experience that’s true only about half the time. Sometimes they must be pointed in the right direction; other times they need to be fished out from between the layers of a rose petal, and at still other times, they must literally be pried off the flower. Apparently, even Japanese beetles have a survival instinct!

Japanese beetles (Popilla japonica) are attracted to the foliage, fruits, and flowers of nearly 300 different plants, among them: roses, crape myrtle, hibiscus, purple-leafed plums, grape leaves, and geraniums.  If you are a Piedmont gardener, chances are very good that you have encountered these pests in recent weeks.

skeletonized squash leaf
A skeletonized rhubarb leaf.

The good news is that Japanese beetles are unlikely to destroy established trees or shrubs. Skeletonized leaves and flowers will grow back once the beetles disappear. The better news is that within 30 – 45 days of their onset they will be gone.

Here are some takeaways to help you cope with Japanese Beetle “Season.”
1. Only one generation occurs each year. They typically emerge in early June and are gone by mid-July. You may see an isolated beetle during the rest of the year but ground zero is late May until early July.

2. Beetles emerge when the temperature is “just right.” Scientifically this equates to approximately 1,000 growing degree days. (Here’s a scientific explanation of growing degree days.)  If the weather heats up faster beetles are likely to appear sooner. Weather conditions also determine the grub population, their larval stage. Damper weather typically means more grubs. More grubs mean more beetles.

3. Japanese beetle traps should not be considered control devices. Designed to attract beetles, rather than trap them, they can increase the beetle population in your back yard. Furthermore, if not emptied every couple of days, the beetles will rot inside, releasing an ammonia which repels them. Instead of going into the trap, they are likely to tap your hibiscus.

4. Where practical, cover the plant with light netting.

5. Just say “no” to things they don’t like. But who could imagine a garden without roses?

6. Rose experts advise picking your roses and bringing them inside. They can beautify your property the rest of the year.

7. Japanese beetles aggregate in response to odor released by damaged plants and a pheromone released by female beetles. I usually cut the least-damaged roses and leave one or two that have been attacked. They are always one of my best beetle-harvest sites.

Beetles in every corner of beat up rose
There are at least eight beetles in this “trap.”

8. Another tip, before cutting a rose to bring inside,

Rose closed sepals
Because the sepals haven’t fallen, this rose, if cut, will not open.

be sure the sepals have fallen or the rose will not bloom.

9. You can, of course use insecticides, a discussion of which is outside of this posting. However, any insecticide will have some negative effect on other insects, including those which are beneficial. The North Carolina Agricultural Chemicals Manual lists pesticides and their relative safety for bees. Should you opt for an insecticide, prune all the flowers first. There are label restrictions against using most insecticides on flowering plants and when pollinators are present. Read the label for detailed restrictions.

10. Insecticides only treat the exposed petals. So, if a bud opens throughout the day, the unprotected petals are just another meal. And, unless they are systemic, insecticides must be reapplied after a rain.

My bottom line strategy: I cut my best roses and leave a few that have already been attacked as traps. Several times a day, I am single-mindedly devoted to search and destroy missions, first dumping the beetles into a container of water soapy water then  finishing with a flush down the toilet.

Further Reading:

Japanese Beetles on Ornamental Landscape Plants

Japanese Beetles

Insects: Japanese Beetles