The presence of brown, dying patches in a lawn often leads homeowners to suspect an infestation of white grubs, the larval stage of beetles like the Japanese beetle or European chafer. When clover, a common lawn component, also appears to be struggling, the question arises: do these destructive pests target the roots of clover? Understanding grub dietary preferences is key to accurately diagnosing and treating lawn issues.
Grub Feeding Habits and Clover’s Root Structure
White grubs primarily feed on the fine, fibrous root systems of turfgrass. They seek out the tender, easily digestible roots of grasses like Kentucky bluegrass and perennial ryegrass for the starches and sugars they contain. This preference is so strong that white clover (a Trifolium species) is often considered resistant to grub damage.
Clover roots are chemically and structurally different from grass roots, making them a poor food source for the grubs. Clover, a legume, develops a deeper taproot structure, unlike the dense, shallow root mat of turfgrass. The roots of white clover contain lignin, a complex polymer that is difficult for grubs to break down and digest.
Grubs actively avoid clover and instead concentrate their feeding on the nearby grass roots. Lawns with a significant percentage of clover often experience less overall damage from grubs because the clover fills in spaces where the grass has been destroyed. The clover also contributes nitrogen to the soil, which helps the surrounding grass recover more quickly from the feeding damage.
Identifying the Signs of Grub Infestation in a Lawn
An infestation of white grubs can still cause widespread damage to the turfgrass around it. The most common sign of a grub problem is the appearance of irregular, brown patches of grass that resemble drought stress but do not recover with watering. This discoloration occurs because the grubs have severed the root system, preventing the plant from absorbing moisture and nutrients.
A more definitive diagnostic sign is the spongy feel of the turf when walking over the affected area. If the grass can be easily lifted or rolled back like a piece of carpet, this confirms the roots have been eaten away and detached from the soil. The grubs themselves, which are creamy white with six legs and a brown head, can then be found curled up beneath the sod.
Another telltale symptom is an increase in activity from predatory animals, such as skunks, raccoons, or birds, which are digging up the lawn to feast on the grubs. To confirm a significant infestation, a small square foot section of turf and soil should be examined. Finding more than five to ten grubs in this single area is generally considered the threshold for an economically damaging population.
Non-Grub Causes of Clover Root Damage
If the clover in your lawn is dying while the surrounding grass is also failing, and a grub infestation is ruled out, the cause is likely a different pest or an environmental condition.
Insect Pests
One specific pest that targets clover is the Clover Root Weevil (Sitona lepidus), whose larvae are legless and white-headed, unlike the C-shaped grubs. These weevil larvae burrow into the clover roots to feed on the nodules, which are responsible for nitrogen fixation, and will consume the entire root system as they grow larger.
Environmental Factors
Poor soil conditions can severely impact clover health. Clover, especially white clover, prefers a soil pH that is slightly acidic to neutral, typically ranging from 6.0 to 7.0. If the soil is too acidic or too alkaline, the plant’s ability to take up nutrients is compromised, leading to decline.
Heavy soil compaction is another common culprit, as the deep taproot of clover struggles to penetrate dense, compressed soil. Conversely, over-fertilization with nitrogen can indirectly harm clover by boosting the growth of the surrounding grass, which then outcompetes and smothers the lower-growing clover plants. Finally, various fungal diseases, such as Sclerotinia crown and stem rot, can cause the plant to wilt and die, even if the root structure is intact.