Changes in ethylene production and monoterpene concentration i

concentration and size of induced lesions were determined following inoculation of stems of slash pine (Pinus elliottii Englm. var. elliottii) and loblolly pine (Pinus taeda L.) with Ophiostoma minus (Hedgc.) H.P. Sydow, O. ips (Rumb.) Nannf or sterile water. In a second experiment, the rate of ethylene production and monoterpene concentration were determined following inoculation of slash pine stems with O. minus, O. nigrocarpa (Davids.) DeHoog (a nonpathogen) or sterile water. Fungal inoculation significantly increased the rate of ethylene production compared with that of stems inoculated with sterile water. Greater rates of ethylene production were associated with greater fungal virulence. Changes in monoterpene concentration generally mimicked changes in the rate of ethylene production, i.e., high monoterpene concentrations were associated with high rates of ethylene production.