A Survey of Siricid Attack on Radiata Pine in Europe

A survey was made of the older plantations of radiata pine (Pinus radiata D.Don) in Spain, Italy, France. Portugal and England in the period May to August 1966 to determine the extent of attack by siricids.

Of the stands that were considered to contain susceptible host material (non-vigorous trees under full canopy) 78 per cent showed some signs of siricid attack, and 54 per cent yielded insects, mainly larvae. Adult Sirex noctilio, S. cyaneus, S. juvencus and Urocerus gigas were obtained.

The infestations were generally at low levels, apart from one windbreak at Sabaudia (Italy) and they were not important economically. The low levels were presumably due to natural biological control which appears adequate provided the stands are thinned regularly.

The siricids appeared to be attracted most to the occasional trees that had lost their crowns through wind or other mechanical damage.