EXPLOITING COLD-HARDINESS TO SEPARATE PISSODES STROBI (PECK) (COLEOPTERA: CURCULIONIDAE) FROM ASSOCIATED INSECTS IN LEADERS OF PICEA SITCHENSIS (BONG.) CARR.

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Abstract
The cold-hardiness of Pissodes strobi (Peck) and of its insect associates in leaders of Picea sitchensis (Bong.) Carr. was tested to determine whether the insect associates could be retrieved free of P. strobi for use in biological control attempts on P. strobi. Leaders were stored at −8, −16, or −26°C for periods from 1 to 14 days. All P. strobi were dead after 14 days at −16°C, whereas their dipteran predator, Lonchaea corticis Taylor, and hymenopteran parasites, Eurytoma pissodis Girault and Rhopalicus pulchripennis (Crawford), continued development after storage at −26°C. The scarcer Dolichomitus terebrans (Ratzeburg) (Ichneumonidae) survived similarly although we did not always find it in our samples; and the equally scarce Bracon pini (Muesebeck) (Braconidae) seemed susceptible to −26°C but continued development at −16°C. Of the few Allodorus crassigaster (Provancher) (Braconidae) obtained one adult emerged after 7 days at −16°C. These results show that in leader clipping operations now used for attempted control of P. strobi, most of the insect associates could be retrieved from the leaders after suitable cold treatment. Additional tests showed that cold-treated leaders could be stored outdoors in temperatures at least down to −20°C with little effect on adult emergence of insect associates. The field testing also showed that few P. strobi in leaders of P. sitchensis can survive overnight temperatures near −20°C.