TRANSMISSION OF OPHIOSTOMA-IPS (OPHIOSTOMATALES, OPHIOSTOMATACEAE) BYIPS-PINI (COLEOPTERA, SCOLYTIDAE) TO PONDEROSA PINE IN IDAHO

Strial pits on the elytra of unflown Ips pini (Say) carry spores like those of the tree-pathogenic blue-stain fungus Ophiostoma ips (Rumbold ) Nannfeldt, yeast, and other fungi, as seen by scanning electron micr oscopy. O. ips ascospores develop on the walls of pupal chambers in ti le phloem of infested pines and adhere to newly transformed I. pini ad ults. Inoculation of severed pine stem sections with body parts excise d from beetles washed in water or alcohol produced phloem lesions char acteristic of tile hypersensitive wound reaction to O. ips. A fungus, characteristic of O. pini, was isolated from infected wood beneath les ions caused by inoculation with head, prothorax, elytron, and alimenta ry canal. Similar infections and reisolations resulted from inoculatio ns of live trees with an elytron-derived culture that caused necrosis of sapwood radially inward from lesions, and tree mortality when lesio ns encircled the stem.