The first Japanese beetle of the season showed up in the garden several days ago. The beetle actually landed on my arm. That was a big mistake on his part because I immediately tossed him to the chickens.
Those first beetles are forward scouts. Once they arrive, they release a pheromone that attracts other beetles. Before you know it, you have a real problem on your hands.
Sayaka Terada, a garden volunteer at Matthaei Botanical Gardens, told me that in Japan they are called koganemushi, or, in English, “gold bug.” Japanese farmers consider them somewhat of a nuisance because they do some damage on crops such as grapes and soybeans.
They are very beautiful insects if you look at them closely and ignore their destructive habits.
The beetles are emerging from the soil where they spend much of their lives as grubs.
Picking off the beetles and killing them whenever you find them is an adequate way of keeping their numbers down – if you are persistent.
Japanese beetles, like many other insects, have certain types of plants they prefer over others. One of their favorites is evening primrose, a type of weed commonly found in and around gardens. A good strategy is to let the beetles start feeding on the evening primrose; a large number of them will often congregate onto one plant. You can then kill the beetles without having to spray your garden directly.
Over the counter chemical sprays work well in controlling them but chemicals also kill beneficial insects.
There is promising research at Michigan State University that involves introducing naturally occurring microorganisms into the environment to infect the grubs and reduce their population. This new method will be different from the milky-spore treatment that is currently available.
Anyone who has ever planted a garden knows that it is almost impossible to grow cabbage without cabbageworms.
Here in my garden I have yet to see a cabbageworm in the cabbage patch. The Imported Cabbage Worm is the easiest to identify. Those little white butterflies you see fluttering around in the garden are the adult stage of the imported Cabbage Worm. If you look closely, you can spot the eggs they lay. Every time a butterfly lands on a cabbage leaf it lays a single tiny white egg.
The other cabbageworm that causes us trouble is the Cabbage Looper. This worm moves across the plant by arching its body and moving its rear legs forward to the front of its body. Then it stretches out to move its front legs forward, much like an inchworm. You will not see the adult moth of the looper because it flies at night.
My cabbage patch is right next to the chicken run; just a wire fence separates the garden from thirty-five hens. I think they may be intercepting the butterflies before they have a chance to reach my cabbage, although today the butterflies are out in full force.
Both species of cabbageworms chew large holes in the leaves and heads and leave behind large amounts of frass (droppings). The control for them is the same too.
A biological insecticide Bt — sold under the trade name of Thuricide, Dipel and others, is a very effective and safe way to kill cabbageworms without harming beneficial insects. Chemical insecticides easily and rapidly kill the worms but also kill any beneficial insects that happen to be in the garden.
You can try making a homemade cabbageworm killer by mixing two to three parts white baking flour with one part table salt. Dust the cabbage plants with the mixture.
The smaller the cabbageworms, the easier they are to kill – no matter what insecticide you use. So, treat your cabbage plants early before the cabbageworms get a chance to grow.
Someone asked me the other day, “do you spray your garden?” and “what sprays do you use?” I gave her a short list of materials that I found useful in my garden. Most people agree that these materials are OK for organic gardeners.
I have been a fan of Bt (Bacillus thuringiensis) since I started gardening in the 1970’s. It is an insecticide made of naturally occurring bacteria found in garden soil. Only surface feeding caterpillars like cabbageworms are killed by it. Bt must be eaten by the caterpillars in order to work. It does not harm beneficial insects.
Spinosad is another insecticide derived from soil bacteria. The bacterium was discovered in the soil at an abandoned rum distillery, so the story goes. This insecticide kills a wide range of insects. It too must be eaten in order to be effective. This reduces the likelihood that the Spinosad would kill a beneficial insect.
Pyola is a mixture of canola oil and pyrethrins. This effective insecticide has the potential to kill any insect good or bad so be on the lookout for honeybees or other helpful insects before you spray.
For disease control, I use a liquid copper fungicide. The other material I’ve used with mixed results is potassium bicarbonate. Potassium bicarbonate is chemically similar to sodium bicarbonate or baking soda.
You can make your own homemade garden fungicide by mixing one tablespoon of baking soda and one tablespoon of liquid dish soap together in one gallon of water. Just make sure your plants have had plenty of water to drink before you spray this mixture.