Japanese beetles and pumpkin planting

By John Fulton         

[June 18, 2007]  Virtually all areas of Logan County are now acquainted with the Japanese beetle. The continued expansion of the range has reached the far corners of the county, but some areas will experience much higher numbers than others. Japanese beetle adults have a one-half to three-fourths-inch-long body with copper-colored wing covers and a shiny, metallic green head. They are about the size of a fingernail. A key characteristic is prominent white tufts of hair along their sides.

They also have an overwhelming appetite for your favorite rose. Adults feed in herds on many deciduous trees, shrubs and vines such as linden, Japanese maple, sycamore, birch, elm and grape. They generally do not feed on dogwood, forsythia, holly and lilac.

Japanese beetle adults feed on flowers and fruits and skeletonize leaves by eating the leaf tissue between the veins. Severely damaged leaves turn brown and fall from the trees. They look like brown lace. Feeding is normally in the upper portions of trees. Beetles prefer plants in direct sun, so heavily wooded areas are rarely attacked.

Adults can be with us until mid-August. The life cycle is similar to a June bug. After mating, females lay eggs in turf, and the eggs hatch into grubs in August. Grubs feed on plant roots until cold weather drives than deeper into the soil. Adults emerge in summer of the following year.

The bacterial control, milky spore sold as Doom or Grub Attack, is frequently recommended to control Japanese beetle grubs. In our area milky spore is generally not recommended, since it controls only Japanese beetle grubs and not other lawn grubs. Also, Japanese beetle grubs must already be infesting the turf for milky spore to work effectively. Pesticides commonly used for lawn grub control will also control Japanese beetle grubs.

Controlling Japanese beetle grubs does not significantly reduce the number of adult beetles the following year. The beetles are good fliers and easily fly a couple miles in a single flight. Once a small group of beetles establishes itself in an area, they attract others by giving off pheromones for mating and feeding. Evidence suggests that adult beetles are attracted to previously damaged leaves. Therefore, reducing feeding damage now can result in less feeding damage in the future.

Generally pesticide sprays of cabaryl sold as Sevin can reduce damage for up to two weeks, but four to seven days is more likely. Sevin is toxic to bees. Synthetic pyrethroids can also be effective but tend to break down quickly with extreme heat. These would include permethrin and bifenthrin. The Japanese beetle repellent made from Neem has not been shown to be effective. Picking beetles off by hand every couple of days may be just as effective as spraying. When disturbed, the beetles fold their legs and drop to the ground. Covering plants with floating row covers can protect prized roses and ripening fruit. Japanese beetle traps are not recommended since they can actually increase damage by attracting more than they kill.

A number of birds, such as grackles, cardinals and meadowlarks, feed on adult beetles. Two native predator insects and a couple of introduced parasites may help to keep Japanese beetle populations in check. Protect natural enemies by keeping the use of conventional pesticides to a minimum. Although damage looks devastating, Japanese beetle feeding rarely kills plants. Therefore, confine control of beetles to shrubs and small trees near main building entrances and other important landscape locations where damage is obvious. Protecting a prize rose bush or a newly transplanted linden tree is a good idea. The U of I Arboretum decided not to treat anything three years ago and didn't lose any plants.

Pumpkin planting

Father's Day is a good benchmark for planting pumpkins for carving or fall decorations about Halloween. Earlier planted pumpkins are great for display in September and early October but tend to be of poor quality come mid-October.

Vining pumpkins need at least 50-100 square feet per hill, with the larger pumpkins requiring the larger area. Hills should be five to six feet apart, and rows of hills should be 10-15 feet apart. Each hill should have about four seeds per hill, planted about an inch deep. The miniature varieties such as the Jack-Be-Little are sometimes grown in rows with seeds planted every eight-12 inches, then thinned to about two feet apart in the rows.

Fall decoration pumpkins should be cut from the vine before the vine dries in order to have a good stem attached to the pumpkin, but after the color is acceptable.

[Text from file received from John Fulton, University of Illinois Extension, Logan County Unit]