Raspberry clearwing

The raspberry clearwing, Pennisetia hylaeiformis, is a moth of the Sesiidae family. Adults are master mimics, visually resembling wasps, with clear wings and a dark pattern on the body.

The moth has a wingspan of 25–30 mm, with black and yellow banding on the abdomen. The larvae are creamy-white with a brown head, reaching up to 30 mm in length during their development.

Pupae are mobile and move toward the exit hole in the stem shortly before the moth emerges. The life cycle of this species typically spans two years, making them persistent residents in a plantation.

Larvae overwinter inside the root crown or at the base of the raspberry canes, providing them with protection against severe winter temperatures.

The adult moth is highly active during the day, particularly on sunny days in summer, when mating and egg-laying processes occur across the berry patch.

The primary host for this pest is the cultivated raspberry. In some regions, it can also infest blackberries, posing a significant risk to commercial and home gardens alike.

Larvae feed internally by tunneling through the root crown and the base of the stems, effectively destroying the plant's vascular system and nutrient pathways.

As a result of this feeding, the affected stems become stunted, brittle, and often collapse under the weight of the fruit or due to heavy winds.

Infested plants suffer from reduced yield, smaller berry size, and lower sugar content, which significantly lowers the marketability and quality of the harvest.

Severe infestations can lead to the complete death of the cane and eventually the entire bush, significantly reducing the lifespan of a raspberry plantation.

Adult moths begin to emerge in late June, with the peak flight period occurring throughout July and ending by early August, coinciding with the flowering of raspberries.

Females lay eggs individually on the soil surface near the base of the canes or on the lower parts of the raspberry stems, choosing secluded spots for oviposition.

Larvae hatch after approximately two weeks and immediately burrow into the plant tissue, where they continue to feed and grow until their pupation the following season.

The pupal stage occurs in early summer. The pupa pushes itself partially out of the exit hole in the stem before the adult moth emerges to start a new cycle.

Managing this pest requires ongoing vigilance because different generations can overlap, meaning larvae of various ages may be present in the field at any given time.

One of the most indicative signs of a clearwing infestation is the development of galls or localized swellings at the base of the cane, just above the soil level.

Internal inspection of a suspected stem reveals extensive tunneling and frass (larval excrement) left behind as the larvae feed on the inner tissue.

Plants often exhibit signs of general decline, including premature yellowing of leaves, wilting of the top shoots, and an overall lack of vigor compared to healthy canes.

Empty pupal cases remaining in the stems after the moth emerges are a definitive sign that the plantation has been successfully colonized by the clearwing.

In the spring, many infested canes fail to produce new leaves or buds, drying out completely because their vascular connection to the roots has been destroyed.

The most effective management strategy is the physical removal and destruction of infested canes, ensuring that the root crown is cleared out during pruning.

Good agricultural practices, such as minimizing soil disturbance near the cane base, help prevent the creation of favorable environments for egg-laying.

Only certified, pest-free planting stock should be used when establishing new raspberry rows to prevent introducing the clearwing into clean fields.

Chemical control involves targeting adult moths with registered insecticides during the peak flight period to interrupt the lifecycle before eggs are laid.

• Maintaining clean rows by removing weeds that may harbor the pest.
• Using pheromone traps for monitoring and early detection of moth activity.
• Applying biological control agents, such as nematodes or fungal pathogens, to the soil to target larvae.