Japanese Beetle Larvae

Identification of Japanese Beetle Grubs

Japanese beetle larvae or grubs are an off-whitish color and resemble an arc shape or the letter “C”. These grubs live in the soil during development and survive by feeding on the roots of grass. As the grub feeds on the grass roots, it greatly reduces the ability of grass to take up water to withstand stresses of hot, dry weather, thereby causing it to die off or create brown patches above the soil. These brown patches are good indicators that there is a grub infestation present. Lawn control companies can identify these areas when performing inspections for Japanese beetle and Japanese beetle larvae infestations. Grubs can be found in nearby green grassy areas. Early recognition of a grub problem can prevent this kind of damage to the lawn.

Japanese beetle larvae spend months in the soil during their development stages. They become full grown, about 2.5 cm long, in the late months of summer. They survive best in well-maintained, quality grass as found in home lawns, golf courses, parks, cemeteries, etc. However, they can survive in almost any soil in which plants can live.

These ideal grassy areas with the proper level of moisture content are what attract the female Japanese beetle to lay their eggs. Laying their eggs in areas like these results in a higher survival rate, which, in turn, causes an increase in damage to the areas where the grubs develop. As the grubs go through development, they are able to withstand drier soil conditions. If drier soil conditions are present, the developing grubs will dig deeper into the ground until they reach a point where the soil moisture meets the need to finish development.

The presence of many adult Japanese beetles feeding on leaves in an area does not necessarily indicate an infestation of surrounding grassy areas by Japanese beetle larvae. Adults are good fliers and can travel from their emergence location to a suitable adult food source. Therefore, a thorough inspection by an experienced exterminator or lawn control professional should be performed before applying any type of chemical application. Look for areas of brown grass and search in neighboring green areas for grubs and pupae.

Control of the grub stage requires properly timed applications. Young larvae are more susceptible to the applications, whereas more mature larvae are more resistant. Read the label carefully for instructions about the proper use of any pesticide.

The best time to apply insecticides for Japanese beetle grubs is from mid-July until end of September. Granular residuals containing insecticides distributed on soil with a spreader are usually the best applications for Japanese beetles. Contact a lawn and ornamental professional for guidance and assistance to control Japanese beetle populations.