ECTOMYCORRHIZAE ESTABLISHMENT ON DOUGLAS-FIR SEEDLINGS FOLLOWING CHLOROPICRIN TREATMENT TO CONTROL LAMINATED-ROOT ROT DISEASE - ASSESSMENT 4 AND 5 YEARS AFTER OUTPLANTING

Laminated-root rot, caused by Phellinus weirii (Murr.) Gilb., is a ser ious disease affecting Douglas-fir and other commercially important sp ecies of conifers in northwestern North America. Recent work has shown that this fungus is successfully reduced or eliminated by the fumigan t chloropicrin. However, the effect of this biocide on nontarget organ isms, including ectomycorrhizae, is uncertain. Following an initial as sessment of organisms 2 years after application of the fumigant, a rea ssessment of the establishment of ectomycorrhizae on Douglas-fir seedl ings was undertaken 4.5 and 5.5 years following chloropicrin applicati on. Our findings show that in areas around stumps treated with 20% and 100% of the labeled dosage and in areas around non-treated stumps, ch loropicrin did not adversely affect the formation of ectomycorrhizae o n young Douglas-fir seedlings by naturally occurring fungi. No signifi cant effect on the abundance or type of mycorrhizae were detected. On this site, chloropicrin did not affect these mycorrhizal associations, at least for 5 years following application. (C) 1998 Elsevier Science B.V.