Life cycle, population dynamics

• Argyrotaenia ljungiana spends the winter as a pupa in a folded leaf that has fallen to the ground. The emergence of butterflies is early, from March until April. Couplings can take place within a week of emergence. The laying is very dependent on the climatic conditions and it can thus be delayed by several days. It usually takes place until mid-May.

• The eggs are arranged in oopplates comprising ten to a hundred eggs. The incubation time of the eggs longer in the spring and depends on the temperature.
  The larvae are observed from the beginning of May to the end of May, first on leaves and then on the inflorescences.

• The pupation occurs from early June in a silk sheath woven by the larva between the organs attacked. Depending on the climate, we then generally observe or shrink the emergence of butterflies of the 2nd flight:
  • in the northern half of Europe, 2 generations take place. The 2nd flight is maximum in July and may last until August.
  • in the southern half of Europe, 3 generations are observed. The 2nd flight takes place during the second half of June, the 3rd flight is observed during the second half of August.
  • In both cases, the laying takes place on the leaves. The young caterpillars, after consuming the foliage, will migrate to the clusters (main source of food in summer). On the latter, it will cause superficial wounds of the epidermis and pulp until harvest. On this date, the larvae will return to the foliage where they will end their cycle.

• The entry into diapause is quite late depending on the climate. It is not uncommon to find eulias in the autumn in the bunches not collected in the plots of vines in Languedoc.

• Synoptic of the development of Argyrotaenia ijungiana on vine (figure 1)