Japanese Beetle

Adult Japanese Beetles seem to be everywhere from late June through July, munching away on your much-loved garden plants. Take heart in the fact that they are typically around for up to six weeks and won't likely do enough damage to kill a plant.

Prevention and control are key in keeping your roses from becoming Beetle food. But where do they come from, and what are they looking for when they arrive?

Life-Cycle
1- Eggs. White, oval shaped and about 1/16 of an inch long.
2- Larvae. Typically white grubs that have a V-shaped series of bristles.
3. Pupae. First a cream color, turning to a light reddish-brown with age.
4. Adult. Brilliant metallic green color, oval in shape. The wing-covers are coppery brown.

The larvae usually mature in June, pupate, and emerge as adults any time between the last week of June thru the month of July. During warm weather, the adults crawl onto lower-growing plants to get warm before taking flight. They will immediately seek out sustainable food and begin feeding as soon as possible.

When the adult Japanese Beetle emerges from the soil, it is hungry, and your garden may provide the plants it is looking for. They will eat the leaf tissue between the veins, but will leave the veins behind. The attacked leaves look like lace, and will soon wither and die. Adults often attack flower buds and fruit.

These plants and trees are in the Japanese Beetle’s preferred diet:
Japanese maple, Norway maple, Birch, Pin Oak, Horse Chestnut, Rose of Sharon, Sycamore, Ornamental Apple, Plum, Cherry, Rose, Mountain Ash, Willows, Lindens, Elms, Virginia Creeper, Perennial Hibiscus.

So, what to do?
There are several options for controlling the adult form of the Japanese Beetle.

Japanese Beetles have a hearty appetite, but won't necessarily eat "everything" in your landscape. Habitat modification is a form of cultural control, whereby you plant things that the beetles don't like to eat.

They typically tend to avoid the following plants:
Red maple, Silver maple, Holly, Boxwood, Euonymus, Flowering Dogwood, Cedar, Juniper, Arborvitae, Red Oak, Tulip Tree, Magnolias, Red Mulberry, Forsythia, Privet, Lilac, Spruces, Hydrangeas and Yews.

It is also helpful to avoid additional irrigation during the egg and young grub development stages, which typically take place in Mid July-mid August. The eggs and young grubs thrive in wet soil conditions.

Mechanical Control (or, trapping) is another method. The traps use a mixture of reproduction pheromones and aggregation pheromones to attract adult Japanese Beetles. This method does not produce a significant reduction in the Japanese Beetle grub population, but is effective in controlling adults.

Depending on the amount of affected plants and their size, the least harmful method to your plants is to knock the Japanese Beetles off into a dish of soapy water. Dishwashing soap is highly effective, but should not be sprayed on a tree.

A third option is Chemical Control (Insecticides). There are a number of insecticides that are effective. But keep in mind that they are also effective in greatly reducing or eliminating populations of beneficial insects such as bees and ladybug beetles.

Carbaryl (sold as the product 'Sevin') is highly effective, as are any of the products containing Pyrethrins, Pyrethroids, and Permethins.

Imidacloprid also provides good results and can be found in Ferti-Lome Tree and Shrub Systemic Drench. This should be applied as a drench in April.