What are most gardeners wondering about today? How do I get rid of those dang Japanese beetles!

First, this year’s update and then last year’s repeated article — couldn’t have said it better myself! =)

Now, numbering in the thousands, I plan to get traps as well as use Sevin on my non-flowering plants to combat the JB. If you are not experiencing them this year, maybe it will be next year, but trust me it will happen. Last year’s words of wisdom: “Fortunately, until yesterday I had not experienced an invasion of Japanese Beetles. They have arrived, and I have killed.”

Here is their history, then my story: JBs have been working their way into Minnesota from Wisconsin over the last several years.

Some insects forage on specific garden plants, and some insects like grasshoppers or Japanese Beetles will eat anything. The JBs have their favorites like birch and fruit trees, but once defoliated by skeletonizing the leaves, they move on to other plants. Some of their favorites are plum, apple, rose and Norway Maple. Secondary choices are Birch, Black Walnut, Beech and Willow.

It’s always best to understand the life cycle of the pest to determine what type of control will work and at what stage to apply controls. The JB voraciously feed on plants starting in July for 6-8 weeks. The adult female can lay 60 or more eggs in her lifetime. During the feeding frenzy time period is when the female is laying eggs in your yard at night. Eventually all the adults die off. Meanwhile, the eggs, which have turned into larvae, are busy chewing on the roots of your turfgrass. As winter sets in, the grubs work their way deeper into the soil.

In the spring when the soil warms, they work their way back up and feed on your turf roots starting about May, creating dead spots in your turf (maybe it wasn’t the dog). After a pupation period, the adult emerges from your lawn in July and begins their destructive process.

For some insects, we only have effective countermeasures at one stage of life, but the JB we can hit in a couple of different ways. As adults: hanging traps can be very effective. There are two main types, one has pheromones that attract the females, and another type is more of a plant scent stimulant that attracts both sexes. So, what is the drawback? These alluring traps can draw insects in from over 1,000 feet away … which could be from your neighbor down the block.

Place the traps on the outskirts of your yard. Heavy infestations can fill traps quickly, so be vigilant. As an extra bonus, place a bucket or tub of soapy water under the trap. As they fight to get in the trap, some are likely to fall — kerplunk. Another method to destroy is to handpick into a can/jar of soapy water or float a little oil on the water. For huge herds, place a pail of the water mix under branches and tap off as many as you can. The last method to kill adults would be chemicals, either a spray/dust type or systemic. Because most garden products kill friend and foe insects, use with caution, if at all.

If you had adults in your yard, you likely have larvae in your turf. The best way to kill the larvae is to apply a product that contains milky spore. Milky spore is a bacterium that will only affect the Japanese beetles in the larvae stage. After the beetle consumes some of it through feeding in the soil, it will die and the spore lives on, multiplying in the soil but harmful to nothing else. The best control is achieved after several years when the spores are more populated. The best part is, one application can last 20 years.

Applying milky spore doesn’t mean that new beetles won’t move in every year, we need to attack them on both ends. The best result would be to get your neighbors on board as well, as another yard in close proximity will have the same issues you will. What is the action threshold? How many JB do I need to see before doing something? One in my book.

My story is simple. Yesterday, as I noticed them in large masses feeding on my grapevines and porcelain vines, I dusted them with Sevin. Within 3 hours, there were piles of dead beetles on the ground and none on the plants. None of these plants were flowering so likely no bees were harmed. End of story

Visit us at the Mankato Farmers’ Market! We are located at the Best Buy parking lot on Adams Street.

Saturdays’ 8 a.m. – noon, Tuesdays and Thursdays from 3:30-6:00 p.m. – both at Best Buy. You can follow my Facebook business page at Market Bakery.

Trending Video