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 Survey Methods

In order to plan and implement appropriate control strategies for the Japanese beetle, you must first survey your property for both grubs and adult beetles.

Traps for adult beetles operate primarily with two chemical lures. A combination of a pheromone, or sex attractant, and a floral lure attract both male and female adult beetles to the trap. Then, as a result of their clumsy flying and the design of the trap, they end up caught in either the bag or funnel portion of the trap.

Japanese beetle traps can be used to assess the beetle population in a given area. For instance, if you put a trap out while the adults are flying and find that beetles fill the trap in 1 day, you probably have a Japanese beetle problem. If, during a week, the bottom of the trap is barely filled, you probably do not need to be concerned. Adult beetles can fly long distances, so those caught in your yard may have come from several hundred yards away. For this reason, it is difficult to estimate the number of grubs in your turf from adult trap catches.

To survey for grubs, you need to calculate the number of Japanese beetle grubs per square foot in your lawn. This estimate is important for deciding the severity of your white-grub problem and whether treatment is necessary.

Japanese beetle grubs can be sampled in late summer (August to October) and late spring (April to June). Timing will vary by geographic location.

If your lawn has brown or dead areas during the normal growing season, survey near the edge of the damage. If you find that grubs are the cause of the damage, clearly this area should be treated. Otherwise, take several randomly selected samples throughout the lawn. The density of Japanese beetle grubs often varies widely within a small area. By taking several samples, you may be able to pinpoint the damage and therefore selectively treat specific areas rather than the whole lawn. 6