Three indicator species [rye (Secale cereale L.), radish (Raphanus sativus L.), and alfalfa (Medicago sativa L.)] and nonrooted cuttings of `Stevens' cranberry (Vaccinium macrocarpon Ait.) vines were grown in pots to establish the dose response levels for a sand-applied phytotoxin(s) from a crude extract of Pseudomonas syringae (strain 3366) culture. At 114 ppm [milligrams phytotoxin(s)/kilograms sand], the material was noninhibitory, whereas 1140 ppm reduced root and shoot growth significantly in all four species. In subsequent experiments, a 10-ppm dose controlled corn spurry (Spergula arvensis L.) and fireweed (Epilobium angustifolium L.) seedlings, while 103 ppm reduced root or shoot growth of cuttings of the perennial weeds birdsfoot trefoil (Lotus corniculatus L.) and silverleaf (Potentilla pacifica Howell). Root and shoot growth of partially rooted `McFarlin' cranberry vines was reduced at 103 and 563 ppm, respectively. The phytotoxin(s) could potentially control germinating annual weeds in newly established `Stevens' cranberry bogs.