Aphids are common, soft-bodied insects frequently encountered in gardens and landscapes. They are sap-sucking pests that use specialized mouthparts to withdraw nutrients from plant tissues. While many species prefer flowers, shrubs, or vegetable crops, homeowners often worry if these insects threaten a well-maintained lawn. This article explores the specific aphid species that attack turfgrass and provides guidance on how to identify and manage the resulting damage.
Do Aphids Target Lawn Grass?
The majority of the over 1,000 aphid species in North America do not target turfgrass. However, a few specific types, most notably the Greenbug (Schizaphis graminum), are serious pests of lawns. The Greenbug prefers certain grass varieties, including Kentucky bluegrass, bentgrass, and various fescues. Large populations of this insect can cause widespread damage to an otherwise healthy lawn.
Greenbugs feed by inserting needle-like mouthparts, called stylets, into the grass blade to withdraw the plant’s internal sap. During this process, the insect injects salivary juices containing a toxin into the plant tissue. This toxin kills the cells surrounding the feeding site, causing visible injury to the turfgrass.
A single grass plant can support numerous aphids, and heavy infestations can reach several thousand insects per square foot of turf. The continued withdrawal of nutrients and injection of toxins severely weaken the grass, stunting its growth. This makes the turf more susceptible to environmental stressors. Although a mature, healthy plant may not die from aphid damage alone, the turf’s appearance will decline significantly.
Recognizing Aphids and Signs of Damage
Identifying the Greenbug aphid requires close inspection, as the adult insects are very small, typically less than an eighth of an inch long. The turf-specific Greenbug is light green to yellowish-green and has a characteristic pear shape. A distinguishing feature of all aphids is the pair of small, tube-like projections, called cornicles, that extend backward from the hind end of the body.
The insects are usually found on the upper surface of the grass blade, often near the crown or nodes. However, the damage they cause is often easier to spot than the pests themselves. Initial symptoms are subtle, presenting as a barely detectable yellowing of the turf in small, irregular patches.
As feeding continues and the toxin spreads, the yellowed patches progress to a distinct orange or tannish-orange color, giving the lawn a scorched appearance. This discoloration can be easily mistaken for drought stress, nutrient deficiency, or a turf disease like rust. Greenbug damage frequently appears first in shaded areas, such as under a large tree canopy, before spreading to sunnier locations.
Aphids also excrete a sticky, sugary waste product called honeydew. While less visible on a closely mowed lawn than on ornamental plants, this substance can make the grass blades feel tacky to the touch. The honeydew can encourage the growth of a dark fungus known as sooty mold, though this is not always apparent on short turf.
Effective Control Methods
Managing an aphid infestation starts with cultural practices that promote a strong, healthy lawn, allowing it to better tolerate pest pressure. Proper irrigation is particularly helpful, as Greenbugs often thrive in areas suffering from moisture stress. Ensuring adequate fertilization and maintaining the correct mowing height will also bolster the turf’s natural defenses.
Biological control involves encouraging the presence of the aphids’ natural enemies, which often keep pest populations in check. Common predators include lady beetles, lacewings, and parasitic wasps. Planting flowers or shrubs that attract these beneficial insects to the surrounding landscape can help with long-term management.
For localized or minor infestations, a mechanical approach involves dislodging the pests with a strong stream of water from a garden hose. This method is most effective when applied repeatedly and directly to the affected area. However, chemical intervention may be necessary for widespread or persistent problems.
When chemical control is warranted, targeted products should be selected to minimize impact on beneficial insects. Insecticidal soaps and horticultural oils, such as neem oil, are effective options that kill aphids by smothering them. These products require direct contact and may need repeat applications since they have little residual effect.
If a stronger treatment is required, a liquid insecticide is the recommended format, as aphids are present on the grass blades, not in the soil. Granular products are ineffective for this pest. Always follow the label directions precisely, applying the product thoroughly to the infested grass blades. Avoid mowing or irrigation for 24 to 48 hours after application.