TechNotes Tips - Worms & Grubs Archive

Grub (Japanese and masked chafer primarily) damage was reported in many areas of the U.S. in late September 2000. Grub damage can easily be identified by peeling back the turf. If the turf peels back like sod, grub damage is suspect. Upon further inspection the grubs should be present with a little digging. The grubs feed at the soil-thatch interface resulting in a pruning of the roots. Thus the turf is easily pulled back like recently laid sod.

Webbing that appears at the branches' ends is most likely the work of the fall webworm. The adult moth lays several hundred eggs in mass on the underside of leaves. Small pale yellow to dark green caterpillars hatch from the eggs feeding on the leaves under the webbing. As the caterpillars continue to feed, the webbing increases. Initially the leaves are skeletonized, but as soon as the caterpillars are large enough, they will devour the entire leaf. A hundred different tree species can be attacked by the fall webworm. Cultural control is achieved by putting on a glove and tearing apart the webbing (nest) or pruning out the nest. Insecticides are also available for control.

Homeowners may find laying on their lawns two-inch long sacs. These sacs look like hand-rolled cigarettes. Although the homeowner might be startled by the presence of these sacs or "silk liners", they are produced by the borrowing sod webworm (Acrolophus popeanuellus). This insect will not cause turfgrass damage and thus, control measures are not necessary in most of the U.S.

Finding grubs (Japanese beetle or masked chafer larvae) in home lawns is not uncommon in late April. Homeowners may be out edging landscape beds, or gardening and finding white grubs as they remove the sod. Although the presence of grubs at this time may raise concern with your customers, little damage is to be expected (they are not feeding). These grubs did most of their feeding last fall. Grub control should be targeted for the emergence of these grubs in August. During spring, attempting to solely control the grubs present is not advisable (unless you are making an application preventatively for grubs later in the summer).

Pine needle miner larvae begin to feed inside the needles of pine trees during spring. Damaged needles appear yellow then dry up.

Common Bagworm (Thyridopteryx ephemeraefromis) is a caterpillar that can cause dieback on a number of conifers and deciduous trees. The most common hosts for bagworms are arborvitae, cedar and juniper. Bagworms appear throughout the year but are most noticeable when mature. This is normally during autumn. Control is often difficult, but if infestation is not heavy, picking them off is an effective control strategy. In 1999 bagworm populations were not as high as in 1998 for most of the Midwest.

Grubs grow larger and cause turfgrass damage in many parts of the country around the beginnig of September. If grub damage is suspected, the turf should peel back like newly laid sod. Another sign that grubs are present is if raccoons or skunks are digging through the turf. The grubs should be visible at the thatch-soil interface.

Grub damage was still present in many parts of the country as of Oct. 1999. Raccoons, skunks and other animals were tearing up turf while scavenging for food. Grubs in the northern U.S., for the most part, had stopped feeding on plant roots. These grubs were starting to move down into the soil profile to begin overwintering.

Sod webworm populations were extremely high throughout the Midwest in July 1999. These populations tend to attract large numbers of birds who peck at the turf. In addition, skunks, raccoons and other such animals may dig up the turf to get to these grubs.