Japanese Beetle Control

Hello! Thank you to everyone who participated in our last survey. From your submissions, it sounds like many of you are in the thick of your peak summer seasons, enjoying lots of blooms and battling the big three: pests, disease, and weeds. We’re talk more about all of these and how we approach them during the August Instagram Live session on IPM (integrated pest management). I’m looking forward to pulling in our own expert, Kyle

For many of us, Japanese beetles are one of the most destructive pests. I’ll start by saying: I have no cure for you. There’s no easy way out.

I’m not even going to suggest to you that you should collect or destroy them in some manner. And I’m definitely not weighing in on the “beetle trap” debate. I’ve found that people are pretty set in their opinions about wether beetle traps help or hurt their crops.

Instead, I’m going to share some resources for you that fall in line with our practice of “working with nature and not against it.”

1. Learn how their life cycle works. From Michigan State University:

   “Egg laying occurs mainly in July and August in the vicinity of the feeding sites. A female lays 40 to 60 eggs in her life, preferring moist soil with grassy cover. The female beetle digs about 10 cm into the soil several times over a period of about two weeks, each time laying eggs in small batches.” If you have open spaces with grassy cover or you grow without landscape cover, it may be easier for Japanese beetle populations to grow on your land. Japanese beetles like a well-watered growing area. They need a moist area for their larvae to develop. Suggestion: don’t curate a well-watered lawn/Japanese beetle breeding ground near your flowers.

2. Step back and note if there are weeds on your property that are luring the bad guys in. Remove those weeds. Here are some common weeds that Japanese beetles like to eat:

   wild grape • Smartweed • ground elder • mallow • poison ivy • multiflora rose • raspberry • virginia creeper • dogwoods • knotweed • morning glory • buck thorn • maple • pin oak

3. Next, consider growing flowers the beetles DON’T LIKE. There is no “one size” fits all flower farm plan. Grow the things that work for you. If you don’t have time or energy to battle the bug-ridden plants, start crafting a plan to work differently. Many of the plants that the beetles dislike are perennials! In a way, these hardy flowers that can survive the winters are telling us “HELLO! I’m SUPPOSED to be here.” AND it’s not too late to start perennials from seed for blooms next season. Most perennials require vernalization - a cold/winter period to initiate mature growth and a flowering season. Here is a list of perennial plants for that are blooming now here in zone 4 and that are untouched by Japanese beetles on our farm. This is our experience. Yours may be different. I had to go hunting this morning to try and find any beetles. (They are really concentrated on the asparagus right now. That was the only place I found any.)

   yarrow • astrantia • veronica • milkweed (and milkweed family plants like tweedia) • centaurea • coreopsis • dianthus • baby’s breath • delphinium • foxglove • blanketflower • sweet peas • gayfeather • daisies • lilies • bee balm • forget me nots • catmint • flowering tobacco • mint • oregano • poppies • obedient plant • rudbeckia • scabiosa • sedum • snowberry • tansy • verbena • feverfew • lunaria • echinacea

4. If you are going to grow “all the things” know that these varieties are likely to attract Japanese beetles. ACCEPT that you will have some losses, unless you’re going to be some sort of crazy vigilante and lose sleep over the a$$holes to capture every last one. If you are growing flowers on the side — the bugs will be there eating your flowers while you’re at your day job. ALSO, remember that bit about them laying eggs near where they feed? When you grow Japanese beetle food, you grow Japanese beetles. Every female will produce 40-60 eggs near where she feeds. I don’t want to crush your flower farming dreams, but I do want to help more growers re-think their commitments to “trendy” flowers. Just because someone else somewhere else in the country or world grows something and makes a beautiful video about it, doesn’t mean we should spend too much time doing the same.

   →East Coast vs. West Coast US comparison: Japanese beetles ONLY started to be seen in Washington state in 2020. The first one was spotted in a parking lot there. According to an article published just a few days ago , the Japanese beetle population is growing in that state, but only one beetle has been found outside of Seattle.

   Here are some favorite Japanese beetle foods.

   dahlias • hollyhock • zinnias • roses • marigolds • sunflower • hibiscus • daylily • gladiolus • cosmos

5. If you grow flowers that attract beetles, consider companion planting them with varieties that will discourage the Japanese beetles. Here is a list of plants that can be added to your landscaping or mixed perennial beds to discourage Japanese beetles.

   • rue: rue is known as one of the most pest resistant plants! But beware, its oils can cause a phytophotodermatitis rash. “Rue Rash” isn’t painful but it can LOOK like severe burns. We avoid the rue in our garden on sunny days and wear long sleeves when working around it. Rue CAN be a beautiful addition to arrangements that customers won’t be touching or that will be enjoyed inside. We love it’s blue-green color (like eucalyptus) and we’ve used it in centerpieces before.

   • catnip: a component in catnip has been compared to products like DEET and been proven effective against ticks and coackroaches! It wards off other pests, too.

   • garlic: a homemade garlic spray may help deter the beetles from your plants

   •geranium: Japanese beetles are interested in the plants, but they become temporarily paralyzed after consuming them. From the USDA: “Within 30 minutes of consuming geranium petals, the beetle rolls over on its back, its legs and antennae slowly twitch, and it remains paralyzed for several hours. The beetles typically recover within 24 hours, but they often succumb to death after predators spot and devour the beetles while they are helpless.”

6. Plant some trap plants (use favorite foods of the beetles listed above) at the perimeter of your property to collect the beetles before the reach your other crops. Be sure to clean your “plant traps” and collect and dispose of the beetles, so they don’t just grow a huge population over time near your flowers. Asparagus can be a great trap plant. The ferny, airy leaves grow about 8ft tall (acting like a sort of tall barrier) and beetles love them.