IMPACT OF EXTERNAL FACTORS ON THE POPULATION-DYNAMICS OF BEECH SCALE (CRYPTOCOCCUS-FAGISUGA) (HOM., PSEUDOCOCCIDAE) IN BEECH (FAGUS-SYLVATICA) STANDS DURING THE LATENCY STAGE

Within a natural occurrence of beech on weathered lime stone in the hi lly region of southern Lower Saxony, the infestation dynamics of Crypt ococcus fagisuga as dependent on the flushing status of its host, Fagu s sylvatica, were investigated from 1988 to 1995 during the latency st age. Employing subpopulations on microstands with different water supp ly and under different silvicultural treatment but with equally good n utritional status, the infestation dynamics of the scale were compared by means of a differential analysis. Independent of the year of obser vation, the microstand, and the silvicultural treatment, beeches with a bhd < 10 cm flushed quicker and showed a lesser degree of infestatio n than beeches of bhd 10-20 cm and > 20 cm. In almost all cases the be eches of the higher diameter classes on the strongly thinned plots wer e attacked markedly stronger than the corresponding ones on the modera tely thinned plots. Increasing infestation was promoted by a decreasin g flushing status on dry stands and by an increasing flushing status o n moister stands. With heavier thinning or stronger self-differentiati on on the more humid stands, heavier infestation was promoted too by d ecreasing flushing status. The gradual transition was stopped when an equilibrium was reached comparable to the level of infestation of stro ngly thinned stands on dryer locations.