The importance of needle compounds on the predisposition of five pine species to the attack by Thaumetopoea pityocampa (Schiff.)
1987
Schopf, R. (Goettingen Univ. (Germany, F.R.). Inst. fuer Forstzoologie) | Avtzis, N.
Five pine species tested in a field plot near Thessaloniki, Greece, were differently predisposed to the attack by Thaumetopoea pityocampa (Schiff.). After 30 days larval mortality amounted to 18.3 per cent on Pinus radiata, 32.6 per cent on P. maritima, 40.7 per cent on P. halepensis; 43.2 per cent on P. brutia, and 82.3 per cent on P. pinea. The concentrations of the soluble carbohydrates (glucose, fructose), inositol, pinitol, shikimic and quinic acid, protein-bound amino acids, and total phenols were determined in the needles of the infested branches and in the larval faeces. On the basis of1306these results relative metabolization rates delta (N)(K) of the particular compounds were calculated. As a measure of needle hardness the content of SiO2 was estimated. The concentrations of soluble carbohydrates, cyclitols, acids and protein-bound amino acids in the needles and the faeces as well the metabolization rates of these compounds were inapprobiate parameters to characterize the different degrees of susceptibility of the pine species. On a significant level the larval mortality of T. pityocampa positively correlated with the concentration of silica in the needles and the metabolization rate delta (N)(K) of the total phenols (folin-positive compounds). Furthermore a negative correlation was found between larval mortality and the concentration of total phenols (vanillin-positive compounds) in the fae
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