White Grub

Phyllophaga spp.

Content coming soon for this insect guide.

Insect Profile

Beneficial Rating

-5 Pest

Active Months

JanFebMarAprMayJunJulAugSepOctNovDec

US Distribution

NortheastSoutheastMidwestSouthwestWestPacific Northwest

Habitat Preferences

gardenslawnsturfgrassagricultural fieldsmeadows

Taxonomic Group

Beetle

Order

Coleoptera

Family

Scarabaeidae

Lifecycle

White grubs are the larvae of various scarab beetles, primarily from the genus Phyllophaga (May/June beetles), but also including Japanese beetles (Popillia japonica) and others. The typical life cycle lasts one year. Adult beetles emerge from the soil from late spring to mid-summer (May-July) to mate. Females then burrow a few inches into the soil to lay 60-75 eggs. These eggs hatch into small larvae, or grubs, in about two to three weeks. The grubs are C-shaped, white, with a reddish-brown head and six legs. They feed voraciously on the roots of grasses and other plants throughout the summer and early fall, molting twice as they grow up to 40mm in length. The third larval stage, which is the most damaging, lasts for approximately nine months. As temperatures drop, the mature grubs burrow deeper into the soil to overwinter. They become active again in the spring, feeding for a short time before pupating and emerging as adult beetles to repeat the cycle.

Overwintering Strategy

Grubs burrow deeper into the soil and overwinter as mature larvae.

Native Range

North America

Attracted By

grass rootsornamental plant rootspotatoesstrawberriesraspberrieslettucedeciduous trees and shrubs (adults)

Repelled By

lavendermarigoldspeppermintgarlic

Organic Control Methods

Several organic methods are effective for controlling white grubs. The application of beneficial nematodes, microscopic roundworms of species like Steinernema feltiae or Heterorhabditis bacteriophora, is a highly recommended biological control. These nematodes actively seek out grubs in the soil, penetrate their bodies, and release a bacterium that kills the host. Another biological option is Milky Spore (Paenibacillus popilliae), a bacterium that grubs ingest, causing them to die from a disease. It is most effective when soil temperatures are above 65°F and can provide long-term control. Bacillus thuringiensis var. galleriae (Bt) is another soil-dwelling bacterium that can be applied to the soil; when ingested by grubs, it disrupts their digestive system and leads to death. For immediate but labor-intensive control, tilling the soil in garden beds can expose grubs to the surface, where they can be handpicked and removed or left for birds and other predators to eat.

Companion Planting

Companion planting with certain aromatic plants can help deter the adult beetles from laying eggs, thus reducing grub populations. Lavender (Lavandula) is effective due to its strong scent from linalool and linalyl compounds, which confuses and repels beetles. Planting lavender along borders or in pots near susceptible plants can create a protective barrier. French marigolds (Tagetes patula) are another excellent choice, as they release thiophene from their roots, a chemical that is toxic to many soil pests, including grubs. Peppermint (Mentha piperita), with its strong menthol scent, can also confuse and repel adult beetles. However, mint should be planted in containers to prevent it from spreading aggressively.