Gluttonous Biennial Leafworm

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

The biennial leafworm lives almost everywhere, but it is especially harmful in the southern regions of Russia. Her taste preferences include grapes, dogwood, viburnum, buckthorn and currant, as well as euonymus, thorns, maple with lilacs and a number of other shrubs and trees. Caterpillars of the biennial leafworm often bite into the bases of young shoots, thereby provoking their drying out. Moreover, each of them can easily destroy up to thirty buds, which will certainly affect the volume of the expected harvest

Meet the pest

The biennial leafworm is a harmful butterfly with a wingspan of 13-16 mm. Her hind wings are light gray, and the front ones have a pleasant yellowish-pinkish color and are endowed with a trapezoidal band of a dark brownish shade with a gray-lead border passing along the sides.

Oval flattened eggs of biennial leaf rollers reach 0.8 - 1 mm in size. Initially, they are painted in pale green tones, and a little later they are covered with rather colorful orange specks.

Caterpillars, growing up to 12 - 14 mm, are colored dark red with a spectacular purple tint. Their prothoracic scutes and heads can be either black or dark brown, while the anal scutes of these parasites are always brown. The apices of the abdomens of light brownish pupae are endowed with a pair of chitinized projections.

The wintering of pupae of biennial leafworms takes place in white dense cocoons under the lagging bark, in cracks, crevices, forks of shoots, as well as in the remains of the garter material. Butterflies fly out in the spring when the average daily temperature reaches fifteen to sixteen degrees. This happens approximately in the second or third decade of May. Butterflies of the first generation fly from ten to fifteen days, and they do this throughout the night - from dusk to dawn. Five to seven days after emergence, they begin to lay eggs - one egg per pedicels with bracts and buds, and a little less often on shoots. The total fertility of female biennial leafworms varies from thirty to one hundred eggs.

The embryonic development of parasites takes about a week and a half. Caterpillars first feed on pedicels, and a little later they move on to ovaries and flowers, tightly braiding them with a silky cobweb and thus creating rather peculiar nests. The insatiable caterpillars develop from fifteen to twenty-four days, after which they pupate on the shoot bark, on leaves or among the drying parts of inflorescences.

After one and a half to two weeks, butterflies of the second generation begin to fly out, laying eggs mainly on green grapes (by the way, also one at a time). The voracious caterpillars emerging from them immediately bite into the berries, devouring the seeds and pulp. These parasites are located in the berries in the spider tubes. During the period of their development, they manage to damage from ten to fifteen berries each. The further fate of damaged berries depends on the weather: in the presence of precipitation, they begin to rot, and in dry weather they dry out.

Approximately at the end of August, the caterpillars of the second generation complete their feeding and, having left the forage crops, braided into cocoons, in which they soon pupate. And already in the pupal stage, they remain until next spring. During the year, two generations of biennial leaf rollers have time to develop.

Particularly favorable conditions for the development of gluttonous parasites are air humidity in the range of 70 - 80% and its temperature in the range from 8 to 25 degrees.

How to fight

During the period of mass flight of butterflies of gluttonous parasites, as well as during the massive revival of caterpillars, spraying with such insecticides as Zolon, Chlorophos, Phosphamid, Nurell, Aktellik, Vofatox, Antio, Ripkord is used "," Decis "or" Gardona ".

Among the natural enemies of biennial leaf rollers, various endoparasites can be noted - more than fifty of their species infect pupae and caterpillars of harmful biennial leaf rollers. These include the larvae of the tahin flies, riders from the poacher and ichneumonid families, and many others.

The fertility of female biennial leafworms is significantly reduced, and the eggs laid by them often die en masse when the relative humidity drops to 30 - 40%, and the air temperature exceeds 31 degrees.