Saturday, July 07, 2018 1:00 am
Japanese beetles returning to bug us
Question: My neighbors just told me that they already have seen Japanese beetles on their roses.
Answer: My sources have reported seeing Japanese beetle adults in our area. This is about two weeks earlier than normal this year.
Japanese beetles are native to Japan, China and other parts of Asia. They first were discovered in the United States in 1916. Since then, the Japanese beetle has spread to many states east of the Mississippi River (except Florida), as well as parts of Wisconsin, Minnesota, Iowa, Missouri, Nebraska, Kansas, Arkansas and Oklahoma. Early efforts to control the spread of the beetle were not effective.
Populations of the beetle peaked during the 1990s in Indiana, then began a slow decline as the pest moved on to western states.
It now appears the beetle may be making a comeback in our area.
The life cycle of the Japanese beetle is complex. It is one of a few pests where both adults and larvae do damage.
In late June or early July, adult Japanese beetles emerge from the ground. The beetles are about an inch in length, dark brown and iridescent. The female beetle emerges first and sends out powerful feeding and sex hormones to attract other beetles, especially males.
Favorite plants for Japanese beetle adults are roses, grapes, cannas, smartweed, soybeans and other legumes, corn silks and flowers of all kinds. The beetles feed on leaf tissue, leaving the leaf veins alone. This results in a skeletonized appearance.
The adult females begin to lay eggs in the ground soon after mating. They tend to pick areas where the ground is soft, such as irrigated turf.
Later on in the year, the adults die, leaving their legacy with their young larvae.
In August or early September, the eggs hatch underground into small larvae (worms). The small larvae feed on turf grass roots. If populations are high, the larvae can kill the turf.
The mature larvae will burrow deeper in the soil in the fall to overwinter in a small cell. The following spring, the larvae work their way closer to the surface where they will pupate.
The cycle repeats itself when the adults emerge in late June or July.
Neem is an organic pesticide that kills the adults and repels them from areas. Many organic folks I know simply knock the beetles off flowers or shrubs into a bucket of soapy water where they die quickly. Regardless of what pesticide used (read the labels) try not to spray on flowers where bees also visit. Spraying later in the day can also help avoid bees. Try not to use systemic insecticides (ones that travel within the plant) on flowering plants.
Preventive insecticides such as Merit or Grub-Ex can be applied to lawns in June to prevent grub injury later on. Organic controls such as milky spore have not proved to work reliably in our area.
The Plant Medic, written by Ricky Kemery, appears every other Saturday. Kemery retired as the extension educator for horticulture at the Allen County branch of the Purdue Extension Service.