Effect of nuclear polyhedrosis virus inNeodiprion sertifer (Geoffr.) [Hymenoptera: Diprionidae] at different temperatures

Larvae ofNeodiprion sertifer (Geoff.) were reared on twigs from Scots pine at three different temperatures, 12°C, 18°C and 24°C. The LT₅₀ of virus-infected larvae was 19.3, 9.5 and 4,6 days respectively. In the control the median length of the larval period was 45.7, 29.8 and 22.1 days at the same temperatures. From this results it is concluded that both the LT₅₀ and the length of the larval period are prolonged by low temperature. The medium length of the larval period, however, is relatively more prolonged than is the LT₅₀. Therefore, nuclear polyhedrossis virus may be an effective control agent againstN. sertifer in cool areas even if the LT₅₀ is relatively long.