Nematus sawfly

Taxonomic position. The genus Nematus belongs to the order Hymenoptera and the family Tenthredinidae, commonly known as common sawflies. These insects are significant agricultural and forestry pests, with many species causing extensive damage to ornamental and edible plants across various climate zones.

Host plants. The primary targets for these sawflies are berry-producing shrubs. They are especially notorious for infesting gooseberry and currant plants. Some species are also known to feed on willow, birch, and other deciduous trees, where their larval feeding can cause significant defoliation of the host plants.

Biology and life cycle. Adult sawflies resemble small wasps or flies. Females use a saw-like ovipositor to lay eggs into leaf tissues. The larvae, often called false caterpillars, are the damaging stage. They typically feed gregariously during their early stages, passing through several larval instars before dropping to the soil to pupate within protective cocoons.

Nature of damage. The primary damage is caused by the larvae consuming the leaf lamina. Initial feeding symptoms appear as small, irregular holes in the leaves. As the larvae grow, their consumption increases rapidly, often leading to total defoliation, leaving only the veins behind. This severe leaf loss inhibits the plant's ability to produce fruit and store energy for the following year.

Control measures. Integrated pest management involves several strategies:

• Cultivation of the soil under bushes in autumn and spring to destroy overwintering cocoons.
• Hand-picking larvae during early infestation stages in small gardens.
• Use of biological insecticides or approved contact-action chemicals if the threshold of damage is exceeded.