Why Are There Maggots Inside My Raspberries?

Small white maggots found inside raspberry fruits — sometimes not noticed until the berry is eaten — are raspberry beetle larvae (Byturus tomentosus). The adult beetles are small, grey-brown and inconspicuous; they lay eggs inside the flowers as they open in late spring, and the hatching larvae feed inside the developing berry through the summer. This is one of the most widespread raspberry pests in the UK and Europe, and in a year with heavy beetle populations a significant proportion of the crop can be affected.

The raspberry beetle life cycle

Adults emerge from the soil in June and feed on flower pollen. Females lay eggs inside open flowers in late June and early July for summer-fruiting varieties. The larvae hatch and feed inside the fruit from pollination through to harvest. Fully grown larvae drop to the soil with fallen fruit or when canes are cut and overwinter in the soil before pupating the following year. The key control window is the flowering period — before eggs are laid inside the flower.

Organic control at flowering

A spray of pyrethrin (naturally-derived, short persistence) applied when around 80% of flowers are open kills adult beetles before they lay eggs. The timing is critical — spray too early and adults have not arrived; spray too late and eggs are already inside the flowers. For summer raspberries this is typically late June. Apply in the evening to minimise impact on pollinators — raspberry flowers need bee visits for pollination, so daytime applications that kill bees are counterproductive.

Encouraging predators in the soil

Raspberry beetle larvae and pupae overwinter in the soil beneath the canes. Light cultivation of the soil beneath the row in late winter exposes pupae to bird predation. Avoid deep cultivation that damages roots, but a light surface disturbance brings many pupae within reach of foraging birds, particularly robins and blackbirds, and can reduce the adult population for the following season.

Living with some infestation

In most years, some level of raspberry beetle damage is the norm and is not a crop failure. Affected berries are still safe to eat — the maggots are harmless — but are cosmetically unpleasant. Floating berries in cold water for a few minutes before eating causes any larvae present to exit the fruit.