COMPETITION BETWEEN A BIOLOGICAL-CONTROL FUNGUS, OPHIOSTOMA-PILIFERUM, AND SYMBIONTS OF THE SOUTHERN PINE-BEETLE

A colorless isolate of O. piliferum was paired in a series of competit ive interactions with three fungal symbionts of Dendroctonus frontalis , the southern pine beetle. Two of these fungi, Ceratocystiopsis ranac ulosus and Entomocorticium sp. A, are considered to be mutualists of t he southern pine beetle. The third fungal symbiont, O. minus, is consi dered to be an antagonist. I found strong evidence of differential com petition between O. piliferum and all three symbionts. In primary and secondary resource capture contests on an artificial medium O. pilifer um outcompeted all three fungi. In inoculations of natural substrate, O. piliferum outcompeted the two mutualists but did not outcompete O. minus. The ability of O. piliferum to outcompete beetle mutualists on both artificial and natural substrates indicates promise for this fung us as a biological control agent of the southern pine beetle. However, it may not be able to always prevent colonization by O. minus and the resultant discoloration of colonized wood.