If you've read my blog for any length of time, you know that the most often subjects I write about are growing basil, garlic, weather, and dealing with Japanese beetles. Here we go again.
The beetles you're seeing today are doing their thing - eating, mating, resting on plants in the morning and evening. Their behavior causes more gardener frustration then a July hailstorm (maybe not). JBs will mate into September or so, afterwhich they die.
A year ago these same adults started their one year life as an egg that was laid by female beetles in your yard and yards all around town.
This diagram shows their life cycle much better than my words -
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| Photo from USDA printed with permission by the Sacramento Bee |
In September this summer's generation all die off, some are dying now because they've already lived their ~sixty day summer adult life span.
Back to females - they lay eggs in lawns from the time they emerge in early summer. They prefer cool-season irrigated grass turf (that's why golf courses struggle with Japanese beetle management too). Each female lays between 40 and 60 days during her lifetime. They have simple lives, really. Mate, chew and destroy your plants, mate some more, lay eggs - pick any order.
Eggs laid in lawns develop into white grubs, also called larvae, and will remain below your turf grass until next spring. Technically, they have a much longer life in the soil -- nine-ten months. In May to June, white grubs will pupate for a few weeks before emerging from grass to finish out their one year life as an adult beetle. The cycle begins again.
It's common practice where Japanese beetles are troublesome to kill next year's generation each summer. Makes perfect sense, except. The except part means that even if you treat your lawn this summer, Japanese beetles can still fly in from other lawns and gardens next year. So why should you treat your lawn? I believe everyone has to decide for themselves the best plan for their landscape.
I like to treat my lawn every summer. My concern is for the health of the lawn (white grubs eat grass roots - see the diagram). Lots of white grub chewing can lead to dead areas in the lawn. Damage can get bad, to the point of needing to be re-seeded or sodded this fall or next spring. Critters like raccoons and skunks add to turf destruction by digging to find and eat the grubs.
Another reason I treat my lawn yearly is I like knowing that I'm killing the next generation of adult beetles, even though adult beetles can and will fly in from other areas next summer.
Early August is a great time to apply a lawn product to kill the eggs and white grubs (next year's beetles). Generally only one product is needed per summer.
The best reference chart to view white grub control products, timing and environmental concerns is from Dr. Whitney Cranshaw, Emeritus Entomologist at Colorado State University. View it below or on his very informative fact sheet on Japanese beetle, click here.
Click on the box with angled arrow in upper right corner to open into a larger format.
Whatever product you choose to use, please read all the package instructions,
Two products
are very low to no impact to beneficial insects, people, pets, etc. Beneficial nematodes (mix and spray) and grubGONE! (granular application with spreader). Both products should be available locally at independent garden centers or online.
There is long-term good news on the Japanese beetle battle front. Dr. Cranshaw and the Colorado Department of Agriculture
are responsible for bringing very safe biocontrol agents that specifically attack adult
beetles and white grubs to Denver, Boulder and Pueblo. The program started in 2015. I wrote about
the three controls in 2018 in a Denver Post article, read here. You can also view the twenty PowerPoint slides I've put together on the three agents here. This link can be found on my Japanese beetle website under Fact Sheets, half way down the page.
Efforts continued this summer with additional biocontrol agent releases. I was fortunate to have one of the three agents released in our yard - click here to view my short YouTube videos on the release (there are seven short videos). Link to my YouTube Channel from my blog home page, upper left.
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| Parasitized (white egg on head) JBs released in our yard July 2020 |
I close with this important information about beneficial biocontrols for Japanese beetle management. Down the road, probably way down the road from now, IF/WHEN these biocontrols get well established along the Front Range area, then the use of spray products and or grub control products to kill Japanese beetles should cease entirely.
Otherwise the spray you use on adult beetles, dunking in soapy water and the granular or spray used on lawns WILL also kill the beneficial biocontrol agents. We are not there yet, but I will keep you posted on the progress of the biocontrol releases and establishment. Hopefully any good news will make front page print and online news everywhere in Colorado. Please pass this along.
Additional Resources:
Japanese Beetle Management in Colorado - My Dedicated Japanese Beetle Website
Products to Manage Adult Japanese Beetles All Summer
Cultural Ways to Reduce Japanese Egg Laying all Summer
Plants - From Resistance to Extensive Feeding
Japanese Beetle Fact Sheet 5.601 - Dr. Whitney Cranshaw
Are you saying that my soapy water baths WILL kill some beneficial biocontrol agents?
ReplyDeleteHad hoped that those drowning baths were at least safe for nonbeetles..............
Good question, I hope this makes sense. When/If the winsome fly gets established (one of the three bio agents), then we will need to look at adult beetles and check their heads and back for white dots which are the eggs from the winsome fly. The photo in this blog shows two JBs with small white dots on their heads, these are the eggs from the beneficial winsome fly. The egg will grow into a larva which will begin eating the adult Japanese beetle (basically killing it and it falls to the ground). The larva grows to the pupa stage and will remain a pupa until next spring when a new winsome fly emerges. This egg laying on another insect is called parasitizing. Once Japanese beetles are parasitized by a winsome fly, then we won't want to drown them in soapy water or spray with products, otherwise we'll also kill the winsome fly eggs. Also in the 20-slide PowerPoint (link above) I listed plants that winsome fly and the wasp (which targets overwintering grubs) need to have as food sources, so it's not a bad idea to plant plants that these beneficial predator insects need to eat!
DeleteALSO, the biocontrol agents do not have unintended consequences to hurt other insects, humans, wildlife and pets. They only target adult Japanese beetles or JB larvae.
Thank you,
Betty
In the Denver post you mentioned Gypsophila paniculata (Baby's Breath) as a plant the beetles don't like. Some humans also don't like this plant as it is an invasive species. Please do not recommend that gardener's plant this species - we have seen it invade roadsides in Estes Park, just downwind from what was a nursery decades ago, right next to Rocky Mountain National Park.
ReplyDeleteThanks for the information Ron!
ReplyDeleteBetty
I have noticed that near the geranium plants,there area lot of dead Japanese beetles. Also on every geranium blossom the beetles are dead. Wouldn't it be great if there was something in the geranium plant that would kill the beetles?
ReplyDeleteGreat observation, yes, there have been studies on geraniums and Japanese beetle, here's the link https://academic.oup.com/ee/article/32/4/873/358606.
DeleteEvidently it's the compounds in the flowers that cause them to paralyze, in the lab setting, the beetles recovered after a few hours, but they don't seem to recover in outdoor settings.
There are many dead beetles near my geranium plants. Also I find dead beetles on the geranium blossoms. Could there be something in the geranium plant that would kill Japanese Beetles?
ReplyDeleteGreat observation, yes, there have been studies on geraniums and Japanese beetle, here's the link https://academic.oup.com/ee/article/32/4/873/358606.
DeleteEvidently it's the compounds in the flowers that cause them to paralyze, in the lab setting, the beetles recovered after a few hours, but they don't seem to recover in outdoor settings.
Great observation, yes, there have been studies on geraniums and Japanese beetle, here's the link https://academic.oup.com/ee/article/32/4/873/358606.
DeleteEvidently it's the compounds in the flowers that cause them paralysis, in the lab setting, the beetles recovered after a few hours, but they don't seem to recover in outdoor settings.
I built a buoy from a beetle trap and a 2-liter pop bottle that floats in the local pond (Kettering lake). It attracts the bugs and lets them drop into the pond where they are eaten by the fish and ducks. Works great, and being in the pond, doesn't leave you with beetles all over everything nearby.
ReplyDeletehttp://billllsidlemind.blogspot.com/2017/08/japanese-beetles.html
http://billllsidlemind.blogspot.com/2017/08/japanese-beetles-2.html
One or two of these in our municipal ponds could greatly reduce the population I think.
Hi Billll - very interesting system and glad to hear you're getting good results. Just a reminder (kindly) that the long term research says use of traps will attract more beetles to plants and surrounding areas. I avoid recommending traps of any kind for this reason. I completely understand the visual results (and numbers caught) that give good results for home owners. Your fish and ducks must be very happy with the daytime snacks! Have a great rest of your summer!
ReplyDeleteIn Mamie Eisenhower Park (Dartmouth and S. Colorado) on Aug 29 while riding my bike along Highline Canal, I walked to a tree to get a closer look at the blooms covering the entire tree. Don’t know the type of tree, but it’s just west of the tennis courts. What I thought were bees turned out to be Japanese beetles. I saw that a bloom cluster was covered with at least 10 beetles. Stepping back, I realized that EVERY bloom cluster was covered with as many or more beetles. Have no idea from top to bottom of the tree how to estimate the number of bloom clusters, but the beetles must have numbered in the 100s of thousands. Not sure why I’m sharing but I thought of you, having read your recent articles. As a new flower gardener (as way to combat pandemic-induced boredom), I always enjoy reading your informative articles! (Just read your post about trying to preserve some of my new plants from the coming [9/8/20] cold snap...thank you!)
ReplyDelete