Grundzüge der Populationsdynamik und Bekämpfung der gemeinen Kiefernbuschhorn‐Blattwespe, Diprion pini L .

Summary Investigations made in 1959–1963 in Northern Bavaria on the occasion of an outbreak of Diprion pini showed that the most important density controlling factors were concentrated to Diapause and food plant. In opposition to the perceptions till now D. pini normally had only one generation pro year amerging in May and June overlapped by a two years‐generation emerging in July. The full grown larvae of the first and second wave showed an overground diapause till autumn. The factors determing Diapause are probable photoperiode (length) and temperature (beginning and end). The density of D. pini is essentially influenced by the relationships between soil moisture and quality of nutritions. Drought conditions probably multiplies the percentage of the saccharids in the needles thereby favouring the needle‐eating larvae in several ways.