White Grubs and Japanese Beetles

On June 2, 2011, in Lawn Issues, Services, by Admin

What are White Grubs?



White Grubs are beetle larvae (most commonly Japanese Beetles). They are 1/2 – 1.5 inches long and c-shaped. They have three pair of legs that are located near their head. They destroy lawns by feeding on the roots of grass. This root injury reduces the turf’s ability to take up water and nutrients. Normally, grubs are found in parts of the lawn that receive a lot of sun, not shade.

Signs of Grub Damage:

  • Parts of your lawn begin to wilt
  • Irregular brown patches in your lawn
  • Lawn feels spongy when you walk across it
  • Skunks, raccoons, and birds begin digging in your lawn
  • Dead turf that easily pulls up like carpet

Grub Damage

More Turf Damage

What are Japanese Beetles:

The Japanese beetle is considered the single most important turfgrass-infesting pest in the United States. It was first

discovered in the U.S. in southern New Jersey in 1916. Japanese beetles occur in every state east of the Mississippi River except Florida. It’s spread is apparently governed by temperature and precipitation. The beetle is adapted to a region where the mean summer soil temperature is between 64° and 82°F and winter soil temperatures are above 15°F. Also, beetles thrive in areas where precipitation is rather uniform throughout the year, averaging at least 10 inches during the summer.

Japanese Beetle adults are slightly less than 1/2 inch long, and are shiny, metallic green. They have coppery-brown wing covers that do not entirely cover the abdomen. There are six pairs of patches of white hairs along the sides and back of the body, under the edges of the wings. Males and females have the same markings, but females are typically slightly larger. Newly hatched larvae are approximately 1/8 inch long and translucent creamy white. Once feeding begins, the hindgut appears gray to black.

Plants Attacked and Damage:

Japanese beetle adults do not damage turf but are an important pest of many other plants. They feed on foliage or flowers, and are a major pest of over 300 species of plants, including fruits, vegetables, ornamentals, field and forage crops, and weeds. Norway and Japanese maples, birch, crabapples, puple-leaf plums, roses, mountain ash, and linden are highly preferred ornamental hosts. Adults feed on the upper surface of the foliage of most plants, consuming soft mesophyll tissues between the veins and leaving a lace-like skeleton. Often the upper canopy is defoliated first or most severely. Trees receiving extensive feeding damage turn brown and become partially defoliated.

Japanese beetle grubs feed below-ground and chew on the roots of turf and ornamentals. As result, they reduce the plants ability to take up enough water and nutrients to withstand stresses of hot, dry weather. The first evidence of grub injury in turf appears as localized-patches of pale, dying grass that displays symptoms of drought stress. As grubs develop further and feeding increases, damaged areas rapidly enlarge and coalesce to a point whereby the turf is not well-anchored and can be rolled back like carpet.

Life Cycle:

Japanese beetles have only one generation per year. In mid-June, as soon as they emerge, adult females mate and begin laying eggs. The adults are most active in the afternoon in full-sun. Females leave ornamental plants where they feed and mate, and burrow two to four inches into the soils (under the turf) in a suitable area to lay their eggs. Eggs hatch in about two weeks, after which grubs begin feeding on the roots of turfgrass. The grubs grow quickly and by late-August are nearly full-grown (about one inch long). Mid-summer rainfall and adequate soil moisture are needed to prevent eggs and newly-hatched grubs from drying-out. Adult females instinctively select areas with higher soil moisture content to lay their eggs to ensure survival of their offspring. Older grubs are more drought tolerant and will move deeper into the soil if conditions become dry. Grubs can also withstand high levels of soil moisture, so excessive rainfall or iffigation will not effect them. As soil temperatures cool in the fall, and the first meaningful frost occurs, grubs begin to move deeper into the soil. Grubs overwinter in the soil about two to six inches below the surface, although some may be a deep as 20 inches. They become inactive when soil temperatures fall below 50°F. In the spring, when soil temperatures reach 50°F, the grubs begin to move up into the root-zone to resume feeding for about three to five weeks. Thereafter, the grubs stop feeding and begin creating an earthen cell whereby they transform into adults.

Control Methods for White Grubs:

  • AllGuard is a very effective way to prevent grubs and also treat existing grubs. Purchase AllGuard today for only $25.00 and get ahead of Grubs today!
  • Merit can be applied in June or July. This helps prevent new grub populations. Merit is an effective Insecticide that is for Professional Use Only. Call today for a free quote on getting your lawn sprayed.
  • Preventative treatments are much more effective than curative treatments. Spraying your lawn with long residual insecticides will help prevent Grubs from attaching your lawn! This is one of the six steps of our fertilizer program.

Call us today at 217-347-7500 for more information!!


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