The larvae of several beetle species, commonly known as white grubs, are major pests of turfgrass throughout much of the U.S. (Japanese beetle, Oriental beetle, Masked chafers, European chafer, and the June beetle). Grubs reside just below the soil surface and prefer sunny areas of the lawn. Sloped, well drained areas with heavy thatch are prime locations for grubs. Generally, grubs found in small numbers (0-5 per square foot) aren’t considered a problem on otherwise healthy, well-rooted turf. When grub populations are heavy, however, larvae feeding on the root system cause turf injury. Infested areas first turn pale, then yellow, then brown, and finally die. Areas of affected turf can be easily lifted from the soil like a piece of carpet. In addition, moles, raccoons, skunks, birds, and other animals feed on white grubs. Turf can be heavily damaged by the activities of these animals as they forage for grubs.
In the adult stage, beetle varieties differ in size, color markings and life cycle. At the grub stage though, different varieties are similar in appearance and have a characteristic C-shape. In most cases, adult emergence occurs in early to mid-summer, followed by mating and egg-laying. The eggs hatch and small larvae begin feeding on roots usually in July or early August. Most of the feeding damage is done by the comparatively large third instar larvae, and it is this stage that causes visible turf damage. Over-wintering occurs with larvae moving downward during late October or November into the soil for protection from cold weather. The following Spring, these larvae will move up to feed and replenish food reserves lost during the winter months before moving back down and transforming into the pupa stage. Little if any visible turf damage occurs at this time. A one-year cycle will be completed with beetles emerging from this pupa stage a short time later.
Controls for white grub problems include:
- Reduce soil compaction and thatch level and improve root system with annual core aeration.
- Maintain good soil fertility to help improve turfgrass health and competitive ability.
- Apply grub controls at the appropriate time on the lawn.
- Use proper irrigation techniques.
- Grubs are never a problem in the deep shade, because they prefer the warmer, sunny areas of lawns
- Grubs prefer to infest nice, thick turf (where more food is present)
- Most grub damage occurs in August and September. We recommend inspecting your lawn for grubs at this time of year.
- Only on rare occasions does an entire lawn get infested with grubs. Curative treatments are usually spot-applied.
- To check for grubs, one needs to pull back the turf to inspect it. Affected areas will easily pull away due to damaged roots.
- Varmints will damage turf to feed on grubs (moles, skunks, birds).
- Certain trees and shrubs (crepe myrtle, purple leaf plum, and roses) attract beetles. Lawns with these present are more likely to be infested.
Preventative vs. Curative Grub Controls
Preventative grub controls usually cost more than curative grub controls, but the benefits offered by preventative controls outweigh this cost.
- Preventative controls are more selective (they only affect targeted pests and not other organisms)
- Preventative controls are usually effective for a longer period than curative grub controls.
- Preventative grub controls guard against harm to your lawn.