Larval feeding by Amphimallon majale causes a range of noticeable damage symptoms, particularly in turf and grasslands. As the grubs feed on plant roots, affected plants may begin to yellow, wilt, and eventually die due to their compromised root systems. Young plants are especially vulnerable, often suffering more severe effects. In turf, large patches of grass can detach easily from the soil, similar to rolled-up sod, due to the extensive root loss. Additionally, secondary damage is common, as birds, skunks, raccoons, and other small mammals dig into the soil to feed on the larvae, further disturbing and destroying the turf.

The life cycle of Amphimallon majale and related chafer species is closely tied to seasonal changes and soil conditions. Adult Amphimallon majale beetles are reddish-brown and measure approximately 13–15 mm in length. Adult beetles typically emerge from the soil in June and July, flying during the evening and landing on trees or shrubs to mate. After mating, females descend to the ground at night to lay their eggs in the soil. These eggs are shiny and white and are deposited a few centimeters below the surface.

Eggs of A. majale hatch within about two to four weeks, depending on temperature and moisture levels. The larvae that emerge are white, C-shaped grubs with yellow-brown heads, and can reach up to 30 mm in length when fully grown. These grubs immediately begin feeding on nearby plant roots. However, if soil conditions are too dry, they may delay feeding and move deeper into the soil to avoid desiccation, returning to the root zone only once moisture levels improve.

The larval stage is the longest and most damaging part of the life cycle. Larval development spans two years, during which the grubs feed on the roots of grasses and other plants, particularly in late summer and fall. The most severe feeding damage typically occurs in September when the larvae are at their largest. Feeding can continue into November or December until cold temperatures drive them deeper underground. The larvae overwinter in the soil and are capable of surviving freezing temperatures.

In early spring, often before snow has completely melted, the larvae return to the surface to resume feeding on fresh roots and new shoots. This activity continues until mid- to late May, at which point the fully fed larvae create an earthen cell in the soil where they pupate. Within two to four weeks, adult beetles emerge, beginning the cycle again in early summer.

Preventing European chafer infestations can be particularly challenging due to the pest’s ability to spread from surrounding areas. Even if a homeowner or land manager takes proactive steps to manage the larvae within their own property, nearby untreated yards, boulevards, or naturalized green spaces can serve as ongoing sources of re-infestation. Adult beetles are strong fliers and can travel short distances in search of suitable sites to lay eggs, meaning newly emerged beetles from neighbouring properties can easily colonize well-maintained lawns and turf.

This widespread distribution across urban and suburban landscapes makes coordinated control efforts difficult. While localized treatments may provide temporary relief, long-term success often requires community-wide management and cooperation. The fact that adult beetles are active at dusk and at night, and that larvae live hidden underground, adds to the difficulty of early detection and timely intervention. As a result, even well-managed lawns can continue to suffer damage unless surrounding areas are also addressed.

Larvanem, a biological control product containing the beneficial nematode Heterorhabditis bacteriophora, is an effective tool for suppressing European chafer larvae in turf and grass. These microscopic, soil-dwelling organisms actively seek out and infect chafer grubs, killing them within a few days. Because the nematodes are natural enemies of the larvae and pose no risk to humans, pets, or beneficial insects, Larvanem is a safe and environmentally friendly alternative to chemical insecticides.

For best results, Larvanem should be applied annually as part of a preventative pest management program. Timing is critical—applications are most effective when the larvae are small and actively feeding near the soil surface, typically in late summer to early fall (late August to early September in many regions). Applying during this window ensures that nematodes encounter the grubs when they are most vulnerable. Soil moisture also plays a key role; irrigating before and after application helps nematodes move through the soil and increases their chances of contacting and infecting the larvae.

Consistent yearly treatments can significantly reduce European chafer populations over time. However, because adult beetles can migrate from untreated neighbouring properties, complete eradication is unlikely. Instead, annual Larvanem applications serve as an effective suppression strategy, keeping larval numbers low and minimizing turf damage. Incorporating Larvanem into an integrated pest management (IPM) approach—alongside proper lawn maintenance, aeration, and community coordination—offers the best chance of long-term control.