QUANTITATIVE AND SEASONAL ASSOCIATION OF THE PITCH CANKER FUNGUS, <i>FUSARIUM SUBGLUTINANS</i> F. SP. <i>PINI</i> WITH <i>CONOPHTHORUS RADIATAE</i> (COLEOPTERA: SCOLYTIDAE) AND <i>ERNOBIUS PUNCTULATUS</i> (COLEOPTERA: ANOBIIDAE) WHICH INFEST <i>PINUS RADIATA</i>

Abstract

Abstract The objective of this study was to determine the quantitative and seasonal association between the pitch canker fungus, Fusarium subglutinans f. sp. pini , and two potential beetle vectors, Conophthorus radiatae Hopkins and Ernobius punctulatus Fall. In samples of reared and dissected cones, 21.4 ± 2.5% of C . radiatae and 30.1 ± 8.0% of E . punctulatus adults carried propagules of F . s . pini . Seasonal variation in mean percentage of contaminated C . radiatae and E . punctulatus emerged from cones ranged from 0 to 67% and was highest for both species February through April. In sticky traps 12.5 ± 2.3% and 11.8 ± 3.6% of E . punctulatus and Pityophthorus spp., respectively, were contaminated with propagules of F . s . pini . Conophthorus radiatae and E . punctulatus co-occurred in 26% of the cones. The percentage of cones containing contaminated C . radiatae was greater when E . punctulatus progeny were also contaminated than when E . punctulatus was not. When contamination status of E . punctulatus was not considered, there was no significant difference in C . radiatae contamination between cones with and without E . punctulatus . Because C . radiatae appears to be a vector of the pitch canker fungus, interspecific transmission of inoculum may increase the incidence of this disease. The parasitoid, Cephalonomia utahensis Brues (Hymenoptera: Bethylidae), was frequently observed parasitizing late-instar larvae of E . punctulatus , but was not found on larvae of C . radiatae . Emergence of large numbers of C . utahensis represents another potential source of inoculum for transmission to prey species.