Landscaping & Nursery Information for Home Gardeners

Japanese Beetles - Garden Pests

Japanese beetle traps alone are not effective enough in zones of greatest beetle abundance to protect favored food plant foliage. Spraying with lead  arsenate is also advisable. Such spraying is effective to protect foliage but is less effective than traps for reducing the number of beetles present and prospective. Certain essential requirements must be fulfilled to secure best results with traps as follows: 

In a trap like the illustration use the bait described below. Choose a location where wind will carry the odor toward the beetles and thus attract them to the trap. They fly against the wind. Do not place the trap so close to plants that the beetles will alight on nearby foliagesay 10' to 20' away from nearest trees and shrubs. Locate each trap in full sun, as beetles rarely enter traps in the shade. Hang it from a cross-arm from a pipe post so its funnel will be 3' to 4' above ground and so the beetles will not hit the post  when flying toward the trap. 

The trap form and dimensions are shown in the picture. Both funnel and baffle are made of 30-gage dull galvanized iron soldered smoothly together, the central section of the latter cut away to allow the bait bottle with its 30.5-gage perforated tin plate container to fit in. The ends of the container are fitted with covers, the lower soldered in place, the upper removable. 

The beetle container consists of a two quart mason jar whose ring-cover is soldered an inch above the lower end of the funnel. The jar should have a small drainage hole bored in the bottom. To bore this a 60-grain, 6" electrolon wheel %s" thick run at 10,000' a minute is best. It is necessary to direct a fine stream of water where the cut is to be made while the jar is held against the wheel with moderate pressure; otherwise the jar will crack immediately. 

A 10-gage galvanized iron bail handle inserted through two holes in the top of the funnel and looped in its middle is used to suspend the trap from a hook on the support. 

As many beetles attracted to the trap strike the funnel outside and escape, a trap with openings in the funnel will reduce such losses, so four openings may be made in the funnel 2y2"wide at the bottom, 2f/211 high and 4" wide at the top. The baffle is extended to  the bottom of the aperture, or 4y2" into the funnel. Each flap is 1%" long projects inward at a 35' angle with the side of the funnel, the diagonal edges of the flaps engaging the wings of the baffle. If the flap does not fit tightly against the baffle at these points,  beetles entering from above will get a foothold and may escape. This trap will catch a larger percentage of beetles than the trap without such openings. 

The outside of the trap should be painted light green; the baffle, bait container and inside of the funnel, white. Traps painted thus catch more beetles than those painted otherwise. As the geraniol in the  bait makes the paint peel from the bait container the paint should be resistant to alcohol. 

Geraniol used in the bait must not be confused with geranium oil which is far less attractive to the beetles. Eugenol smells like clove oil llut is much stronger so should always be used. When liquid bait is used it is placed in 1%ounce bottles not more than 13/4" in  diameter, otherwise they will not fit in the containers. The height should not exceed 3" else the wick will contact the top of the container. Cotton lampwick is passed through ,a cork and exposed about 2". If  larger, evaporation will be too rapid; if too short, fewer beetles will be attracted. A bottleful should last five to seven weeks, depending upon the weather. Any bait left at the end of the season may be kept  until the next in a tightly corked amber-colored glass bottle. The formula proportions for liquid bait are: Geraniol (at least 70% pure), 4 teaspoonfuls; eugeno1 (U. S. P.), 1/4 teaspoonful; water, 1 tablespoonful. Pour into an amber-glass bottle, shake vigorously then fill the trap-bottle. 

As beetles are active during the day remove them from the traps late in the evening or early in the morning while more or less torpid, dumping them into a pail of very hot water or water in which is  some kerosene or gasoline. If beetles from several traps are emptied into one pail stir them up to get them wet. Keep the pail covered until all are dead. Many beetles may appear dead when the jars are  opened on warm days. Take nothing for granted: kill them anyway! Beetles killed with hot water may be fed to poultry or used as fertilizer scattered thinly over the ground. 

For information as to manufacturers of traps and materials write the Japanese Beetle Laboratory, Bureau of Entomology, Moorestown, N. J. 

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