Insidious Linseed Moth

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

The flax moth lives almost everywhere, with the exception of the Carpathians. It harms, of course, flax, and both oil flax and fiber flax. These pests especially strongly attack flax in the Central and Northwest regions. At the same time, both larvae and adult flax moths are harmful. Feeding on the tips of the flax crops, they destroy growth points. As a result of such harmful activity, plants are characterized by stunted growth and abnormal branching. Their leaves curl and turn yellow, the buds fall off, and the yield of fibers and seeds is significantly reduced

Meet the pest

The flax moth is a very cute butterfly with a wingspan of 13 to 16 mm. Its front wings are brownish-yellowish in color and equipped with rich brown edges along the edges. And narrow brownish stripes run across the front wings. As for the rear wings, they are painted bright gray.

The size of flax moth eggs reaches about 0.6 mm. Initially, they are characterized by a milky white color, and after some time they become yellowish.

Greenish-yellow caterpillars, growing up to 8 mm in length, are covered with sparse light hairs. The occipital plates and heads in young caterpillars are usually blackish, and in individuals of all subsequent ages, they are brownish. Dark yellow pupae, 14 to 15 mm in size, are endowed with convex abdomens.

The overwintering of caterpillars that have completed their development takes place in fallen flax boxes or in cocoons in the soil. Pest pupation is observed in April and May, and the emergence of adults starts approximately in the second half of May. They fly, as a rule, after the sun goes down, laying eggs on the upper sides of the apical leaves in an amount of two to four pieces. Sometimes eggs can also be found on the inner sides of the sepals. The total fertility of females is from fifty to one hundred and eighty eggs.

After five to seven days (the embryonic development of flax moths never exceeds a week), tiny caterpillars hatch from the eggs laid. First, they eat out the formed ovaries in buds and flowers, thereby provoking their quick death, and some time later they bite into linseed boxes and eat ripening seeds there. As a rule, the development of voracious larvae takes from sixteen to nineteen days. Before pupation, caterpillars gnaw small round holes in linseed bolls, without affecting the outer epidermis.

Approximately in July, seventeen to nineteen days after pupation, the emergence of adults of the second generation is observed, developing in the same way as the adults of the first generation. The flax moth gives only two generations per year. Sometimes there are three, but this happens very rarely. Caterpillars of the latest generation are always sent for wintering.

The loss of seed yield in the case of flax colonization by harmful flax moths can reach 40%.

How to fight

The most effective protective measures against the flax moth are the optimal timing of flax sowing, as well as its fairly quick collection and subsequent threshing (at the stage of early yellow ripeness). Deep fall plowing along with stubble plowing will be equally important activities. All these activities will allow to destroy some of the pupae and caterpillars.

It is recommended to process flaxseeds before sowing with Gamma-Thiuram or Tigam. And seedlings attacked by pests are often dusted with HCH dust.

Insecticide spraying is usually resorted to at the stages of budding and formation of linseed bolls. During the periods of mass oviposition of flax moths, such chemicals as "Fufanon", "Karbofos" or "Bi-58 New" are most often used.