A Homeowner's Handbook - Recognizing Life Stages - Homeowner Controls for Japanese Beetle - Surveying Your Property - Communication as a Tool for Control - Mechanical Traps - Biological Control - Chemical Control 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 up to a mile 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, 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, so by taking several samples, you may be able to pinpoint the damage and therefore selectively treat specific areas rather than the whole lawn.
Using a shovel, dig a square hole 8 by 8 by 3 inches deep in the turf. Turn the sod over on some newspaper and search the grass roots and the soil in the hole for grubs. Turn the turf back into the hole and add water to help the grass recover. Record the number of grubs found in the sample location so you can map out or average grub densities. To convert these numbers to the number of grubs per square foot, multiply them by 2.25. Generally, you should consider treating areas in your lawn with more than 10 grubs/square foot.
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