Dangerous Raspberry Shoot Gall Midge

2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38

Raspberry sprout gall midge loves to feast on not only raspberries - it can often be found on strawberries with blackberries. And she lives in almost all regions where these juicy fragrant berries are grown. The larvae are especially harmful to the shoots - in the places of their feeding, the formation of brownish specks begins, which subsequently turn black and grow, covering rather impressive areas of the shoots. The damaged areas are gradually colonized by saprophytic fungi, and the shoot bark begins to die off, which in turn leads to drying of the stems. It is especially unpleasant that the raspberry shoot gall midge attacks all varieties of raspberries

Meet the pest

The adults of raspberry shoot gall midges grow in size from 2 to 2.5 mm. Due to their small size, it is sometimes difficult to notice them on vegetation. Pests are characterized by a black color, but their backs are almost always brownish. The legs of raspberry shoot gall midges are yellowish-brownish, and their wings evenly cover small hairs.

The eggs of dangerous enemies of raspberries are spindle-shaped and very small in size - their length is only 0.3 mm. The color of the laid eggs gradually changes from milky white to orange. And the larvae of the pests are painted in reddish tones, grow in length from 2, 5 to 4 mm and are endowed with well-developed antennae.

Adult larvae overwinter at the bases of raspberry shoots in reliable cocoons. As soon as the regrowth of shoots begins with the onset of spring, the harmful parasites pupate, and the emergence of adults falls on the stage of intensive growth of young shoots. Years of adults can be observed for two to three weeks.

Females, during their short life span of four to six days, manage to lay from sixty to eighty eggs under the bark of shoots. In addition, they often lay eggs in cracks and other mechanical damage. Most often, eggs are laid in groups, each of which contains up to twelve eggs.

After about two or three days, voracious larvae revive, making their way into the cambial layer under the bark and living there in small groups. As a rule, their development takes from twenty-two to forty days - the more exact dates depend on weather conditions.

During the feeding period of harmful larvae, enzymes and substances are released that cause excessive cell proliferation and the formation of galls - characteristic growths. The size and shape of such growths can be very diverse.

The larvae, which have finished feeding, fall to the soil and pupate in the surface soil layer. Approximately in July-August, adults of the second generation fly out. And in the southern regions, the third generation sometimes develops.

Raspberry shoot gall midges inflict the greatest harm on varieties that bear fruit on last year's shoots. In principle, they often affect annual shoots, however, usually in conjunction with various fungal diseases. Shoots attacked by pests conduct nutrients and water to a much lesser extent, weaken greatly and can even dry out.

How to fight

In early spring and late autumn, the soil under the berry bushes must be well dug up. Infected raspberry shoots should be cut and burned promptly.

Before flowering, and, if necessary, at the end of the harvest, raspberry bushes are treated with insecticides. Typically, such treatments are required when pests infest twenty to twenty-five percent of the berry plantings. Such drugs as "Mospilan" and "Calypso" have proven themselves well in the fight against these pests.

Also, during the entire growing season, the dynamics of egg-laying by pests is controlled using pheromone traps.