%0 Research article
%T Defoliation by the common pine sawfly (Diprion pini) and subsequent growth reduction in Scots pine: a retrospective approach
%A Kurkela, Timo
%A Aalto, Tarmo
%A Varama, Martti
%A Jalkanen, Risto
%D 2005
%J Silva Fennica
%V 39
%N 4
%R doi:10.14214/sf.360
%U https://silvafennica.fi/article/360
%X The foliage status in the main stem of Scots pines (Pinus sylvestris)  was studied retrospectively using the needle trace method (NTM) on a  stand, seriously defoliated by the pine sawfly (Diprion pini) in the  1980s. Needle density increased abruptly in the seasons following the  defoliation. The strongest reduction in annual needle production  occurred one year later. As a consequence of lower needle production,  the annual number of attached needles decreased three to five years  after the defoliation. Needle retention and the average age of attached  needles tended to increase after defoliation. In analyses of covariance  with the NTM variables, needle density (logarithmic transformed values)  and average age of attached needles, had the highest, significant,  negative relationship with radial and height increments both in the  period prior to the defoliation and in the time when the trees were  suffering from defoliation. The relationships between height increment  and the number of needles and needle loss were positive and significant.  Also radial increment had a positive relationship with the number of  needles but not with needle loss. Interestingly, an abrupt increase in  the needle density gave a good indication of the effects of a sudden  defoliation in pines.