The Mechanism of Pathogenicity of Sirex Noctilio on Pinus Radiata II. Effects of S. Noctilio Mucus

Abstract

Effects on P. radiata of a mucus secretion from the female wood wasp are described. When injected into the sapwood, this substance induced the rapid physiological changes in the crown which are characteristic of trees attacked by S. noctilio. Among these was the accumulation of starch in the leaf and a decrease of starch in the bark of the stem implying that the translocation of photosynthate was inhibited. This was followed by premature senescence and abscission of much of the foliage and increased susceptibility to the fungus, Amylostereum sp., which occurs in symbiosis with the insect. Therefore it is concluded that the mucus secretion conditions the tree, which is subsequently killed by the fungus.