Results of Polyhedral Virus Applications Against Neodiprion sertifer Geoffr

In 1972 several experiments were carried out in Lower Austria to study the effect a very early application of a polyhedral virus suspension may have on Neodiprion sertifer Geoffr., feeding on the needles of Finns nigra austriaca and P. silvestris. The results show that spraying in the Li‐stage prevents a major loss of needles, thus confirming the outcome of the 1971 experiments. Especially for young trees or trees that were already partially defoliated the previous year, an early application is of great importance. The effect equalled the result obtained with a malathion‐containing insecticide. With older trees spraying in the L 2 ‐L 3 stage still gave good results.