Spindle ermine

The Spindle ermine moth (Yponomeuta cagnagella) is a member of the Yponomeutidae family within the order Lepidoptera. While primarily associated with the European spindle tree, it is a significant pest of various ornamental and fruit trees, often causing complete defoliation when population levels reach a peak.

The larvae are host-specific feeders, targeting plants mainly in the Euonymus and Prunus genera. The damage is primarily aesthetic and physiological; when trees lose their entire canopy, they suffer from reduced carbohydrate reserves, leading to stunted growth and increased susceptibility to drought or pathogens.

The biological cycle is univoltine, meaning there is only one generation per year. The species overwinters as first-instar larvae under a protective shield secreted by the female. In spring, they emerge to feed on buds and then move to young leaves, constructing characteristic web-like nests that serve as collective shelters.

Damage is characterized by the presence of large, white, silken tents that cover entire branches. Inside these tents, the gregarious larvae skeletonize the leaves, eventually leaving only the midribs. Following the feeding period, they pupate in dense white cocoons arranged in clusters within the silk webbing.

• Manual removal of webs and caterpillar clusters in late spring.
• Application of biological pesticides such as Bacillus thuringiensis.
• Usage of systemic insecticides targeted at the early larval stages.
• Encouraging natural predators like parasitic wasps and insectivorous birds.

Effective management requires scouting for early signs of web formation. Once the silk nests become thick and elaborate, chemical control becomes significantly more difficult, as the protective webbing prevents the insecticide from reaching the larvae. Therefore, timing treatments early in the season is critical.