Etat actuel et activité du Bombyx disparate, Lymantria dispar (Linnaeus, 1758) (Lepidoptera, Erebidae), dans la réserve de biosphère de Chréa (Algérie)

Abstract: Following the latency period of about ten years, Lymantria dispar has been
developing since 2020 towards an epidemic phase in various areas of its distribution in northern Algeria. In elevation, holm oak in the biosphere reserve of Chréa located at 1450 meters, and the holm oak in mixture with the Atlas cedar at 900 meters of altitude are among the main foci of first epidemic infestation detected since 2020. The counting of egg masses conducted according to a systematic plan on holm oak trees in winter 2021 highlighted a number up to 140 egg masses/tree at the altitude of 900 m. At the elevation of 1450 m, the number is limited to a maximum 36 egg masses/tree. Opposing to the density of the egg masses, the fecundity is more consequent in elevation, at this level the females in phase of progradation find a climate more adequate for laying. The difference in density is related to the epidemic status of the pest in its range. Periodic investigations on the movements and migration of the spongy moth can provide more conclusive information on population dynamics and on the pest distribution in its range.