How to Control Earwigs on Dahlias

Earwigs and dahlias have a well-known antagonistic relationship. These nocturnal insects are perfectly sized to shelter inside dahlia flowers during the day, and they spend the night chewing petals, leaves, and young shoots. The good news is that they are easy to trap without any chemicals, once you understand their behaviour.

How to Tell If Earwigs Are the Problem

Earwig damage produces a very specific pattern: irregular, ragged holes and notches around the edges of petals and leaves, often more pronounced on the outer petals of large blooms and on young, tender foliage near growing tips. The damage appears overnight — you may notice healthy flowers in the evening and find them ragged by morning. Unlike slug damage, there is no slime trail. Unlike capsid bug damage, the holes tend to be larger and less regular. Confirm by going out after dark with a torch: earwigs are visible inside flowers and on stems at night.

Why Dahlias Attract Earwigs

Earwigs are attracted to the dense, layered petal structure of dahlia flowers, which provides the dark, sheltered daytime hiding spot they seek. Double and decorative dahlia varieties with many tightly packed petals are particularly susceptible. Ball dahlias and pompons also attract earwigs into their tight centres. Single and semi-double varieties are less affected because there are fewer places for earwigs to hide.

The Upturned Pot Trap — Classic and Effective

The most reliable earwig control method is trapping. Place a bamboo cane or short stick beside each affected dahlia, with an upturned terracotta pot stuffed loosely with straw or screwed-up newspaper balanced on top. Earwigs naturally seek dark, sheltered hiding spots during daylight hours, and a straw-stuffed pot is exactly what they are looking for. Check the traps each morning and either shake the earwigs into a bucket of soapy water to kill them, or take them well away from the garden to release them. Empty and re-stuff the traps every two to three days to keep them attractive.

Other Physical Control Methods

Corrugated cardboard rolled into cylinders and secured with an elastic band, placed at the base of canes, works on the same principle as the pot trap and is easy to make from packaging. Removing ground-level hiding places — loose bark, piles of debris, dense ground cover near dahlia beds — reduces the local earwig population's daytime shelter options and forces them to use your traps. Keeping beds tidy and mulch-free immediately around plant stems also reduces earwig numbers.

Chemical Control

Insecticide dusts containing deltamethrin or similar pyrethroids can be applied around the base of plants and over the soil surface as a barrier. These work by killing earwigs as they move across treated surfaces. The drawback is that pyrethroid dusts and sprays also kill beneficial insects including ground beetles, which are themselves earwig predators. Reserve chemical control for cases where trapping alone cannot manage the population. Always apply in the evening when bees have finished foraging, and avoid getting the product on open flowers.

Keeping a Realistic Perspective

It is worth noting that earwigs also eat aphid eggs and small aphids, making them partly beneficial in the garden. The goal is not to eliminate earwigs entirely but to keep their numbers at a level where dahlia flowers are not seriously damaged. A programme of daily trap checking during peak dahlia season is usually sufficient to protect your blooms without resorting to chemical intervention.

Control Summary

• Confirm earwig damage with an evening inspection using a torch
• Set straw-stuffed upturned pot traps on canes beside each plant
• Check and empty traps every morning during the growing season
• Remove daytime hiding places — debris, bark, loose mulch — near plants
• Use pyrethroid dust as a last resort, applied in the evening