Identifying grubs

Turf-infesting grubs are the larvae of beetles in the scarab family, and several types cause damage to turfgrasses. Their distinctive “C” shape is familiar to most turf managers. However, with only the larval stage present, could you tell one species from another

Identifying grubs is a useful skill because control recommendations—timing and treatment thresholds, for example—vary among species.

Mole, skunk and bird activity and dead or dying patches of turf that pull up without roots are signs that should make you suspicious of a grub infestation. The only sure way to know, however, is to cut into the turf in several locations and look for grubs in the turf root zone. Once you have obtained grub specimens, the next step is to identify the grub species.

The best characteristic to use for grub identification is the rastral pattern—the arrangement of the small hairs and spines on the raster, which is the ventral side of the grubs posterior end (the end opposite the head). This patterning is characteristic for most species. You can view it with a 10x eyepiece, available from many suppliers and surplus outlets.

Although numerous kinds of grubs exist, a relatively small number are responsible for most damaging infestations. Here, we show the most important species you’re likely to encounter. So, with grub in hand, match the raster pattern you see to one shown here and find out which grubs species is bugging your turf.

* The genus Phyllophaga includes more than 100 North American species, which are usually referred to as May or June beetles. Fewere than 10 of these account for most of the damage caused by May or June beetles, and their rasters all resemble the generalized pattern shown here.

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