Lawn grubs are the immature, larval stage of various scarab beetles, including the Japanese Beetle, European Chafer, and June Bug. These larvae live beneath the soil surface, feeding on grass roots and organic matter. Accurately identifying these pests is the first step in determining the appropriate management strategy for lawn damage.
General Physical Characteristics
The most recognizable feature of a lawn grub is its soft, creamy white or grayish-white body, typically curled into a distinctive “C” shape when found in the soil. This characteristic posture is common across most destructive white grub species. The grub’s body is segmented and often appears slightly wrinkled or plump.
At one end of the body is a hardened head capsule, usually a shade of brown ranging from reddish-brown to dark tan. All true white grubs have three pairs of short, jointed legs located on the thorax behind the head. These legs distinguish them from other soil-dwelling larvae, such as legless billbug grubs.
Mature grubs vary in size, generally measuring from about one-half inch to over one inch in length, depending on the species and stage of development. Their size and pale coloration make them noticeable when a section of turf is peeled back or dug up.
Key Differences Among Common Species
While all lawn grubs share the C-shape and white body, distinguishing between species like the Japanese Beetle, European Chafer, and June Bug is important because their life cycles and vulnerabilities differ. The most reliable identification method involves examining the raster, the pattern of tiny hairs and spines on the underside of the grub’s posterior segment.
Japanese beetle grubs are typically smaller at maturity, reaching about three-quarters of an inch, and their raster pattern is a distinct V-shape. European chafer grubs are similar in size but can be slightly larger. Their raster consists of two parallel rows of spines that diverge, or fan out, at the tip of the abdomen.
June bug grubs (larvae of May beetles) are generally the largest, sometimes growing up to an inch and a half long. Their raster pattern is characterized by two parallel lines of spines that converge at both the front and rear ends. A key difference is the life cycle length: Japanese beetle and European chafer grubs usually complete development in one year, while June bug grubs take two to three years to mature.
Habitat and Seasonal Presence
Grubs spend the majority of their lives underground, inhabiting the top layer of soil where grass roots are most abundant. They are typically found within the upper three inches of the soil profile, the primary root zone of turfgrass. Adequate soil moisture is a significant factor, as adult beetles prefer to lay eggs in moist soil for successful hatching.
The timing of their life cycle dictates when grubs are most visible and destructive. Eggs typically hatch in mid-summer, and the small larvae immediately begin heavy feeding throughout the late summer and early fall. This period causes the most noticeable damage to lawns.
As soil temperatures drop in late fall, grubs instinctively burrow deeper into the ground, sometimes several inches below the root zone, to overwinter. They remain dormant until spring when rising temperatures prompt them to move back toward the surface for a brief feeding period before they pupate and transform into adult beetles. Late summer and early fall are the peak times to uncover and treat the largest, most active grubs.