Japanese Beetle Control
Summary: Japanese beetle control is easier said than done. The invading adult Japanese beetle can do serious damage to garden vegetables and flowers. There seem to be as many opinions on how to control them as there are beetles.
Bill; Troy, MI asks: I live in an apartment and every May, I plant several containers with impatiens on my balcony. I buy fresh potting soil every spring to fill these containers. In the past two years I have had a problem with Japanese beetles overtaking my potted plants. I treat with an insecticide, but it seems the flowers don't grow as well after I use this product. It gets rid of the beetles, but I sacrifice the full lush impatiens I have grown before the beetle problem arose. Is there some way I can prevent these beetles from taking over my plants?
Dear Bill: Japanese beetle control must be timed with their seasonal cycles. They come and they go and beetle populations rise and fall. Having been in the lawn care service business for nearly 35 years, we learned to chart Japanese beetle activity as it moved to various areas in a city. Some neighborhoods would get slammed with Japanese beetles, while nearby neighborhoods would be totally passed over. After a couple of years the situation might reverse. We could almost predict what parts of the city would be hit by Japanese beetle outbreaks from year to year.
Japanese beetles love impatiens. The beetles could be flying to your porch from long distances where they have emerged from the ground, enticed by the fragrance of their favorite flower. Even treating the ground directly around your property might have little effect on the total beetle population visiting your balcony. You can protect your potted plants by covering them with cheese cloth or some other type of fine mesh screening to keep the beetles at bay. Some gardeners make sport of it by hand-picking the beetles off their plants everyday. Personally, I'd rather watch paint dry.
The beetle populations will eventually fall to their normal levels as predators like birds, rodents and other insects and parasite populations feast on the burgoning beetle population. It may take a couple of years to see this occur.
Lots of people use those Japanese beetle traps called Bag A Bug traps, containing a power sex attractant. These traps are meant to cover extremely large areas. Putting a trap out in a yard, or in your case, a balcony, will only serve to exasperate the problem by attracting even more beetles to your potted plants. I always find it amusing when people rave about the success they have had catching Japanese beetles in these traps. They fill up a bag and think they have put a dent in the beetle population, not realizing that the beetle populations number in the trillions. So, what does a bag-full of Japanese beetles mean in the big picture? Zero! Don't use them unless you wish to collect thousands of Japanese beetles coming from your neighbors' lawns.
There are various pesticides labeled for Japanese beetle control. Some pesticides are for spraying the grub worm of the Japanese beetle, while others are general sprays that are labeled for treating adult beetles. Treating the adults will require repeated applications. Of course, there's a downside to treating the plants. Not only will you kill off the Japanese beetles, but you'll also kill off beneficial insects that eat aphids and mites. Seems like you just can't win this one.