Seedling Broadleaf Weed Control with MBI-005.  J. C. Neal*, R. Schiavone, and C. Harlow; North Carolina State University, Raleigh NC

MBI-005 is a biopesticide produced by fermentation of Streptomyces acidiscabies RL-110.  The active ingredient is thaxtomin, a non-systemic plant toxin.  This class of chemistry has been reported to have herbicidal activity on dicot weeds with significantly less activity on grasses.  In this research we investigated preemergence and postemergence efficacy of MBI-005 on seedling dicot weeds and compared application concentrations and spray volumes for optimum control.  Experiments reported herein were conducted in outdoor containers.  Increasing the dose of MBI-005 from 19 to 38 L/ha improved preemergence and postemergence efficacy on most species tested.  Applied preemergence, 38 L/ha MBI-005 provided greater than 90% control of eclipta (Eclipta prostrata), spotted spurge (Chamaesyce maculata), henbit (Lamium amplexicaule), dandelion (Taraxacum officinale), marsh yellowcress (Rorippa islandica), pearlwort (Sagina procumbens), common groundsel (Senecio vulgaris) and annual bluegrass (Poa annua).  Postemergence applications were less effective on marsh yellowcress, annual bluegrass , dandelion and pearlwort than were preemergence treatments. Common chickweed (Stellaria media) and hairy vetch (Vicia villosa) were not controlled preemergence or postemergence.  Control of flexuous bittercress (Cardamine flexuosa) was less than 60%.  Sequential treatments improved efficacy of both preemergence and postemergence treatments.  Increasing spray volume and concentration improved postemergence control of flexuous bittercress, common groundsel, dandelion, henbit, and eclipta.  Results suggest that the percent control observed was more a function of the actual dose of MBI-005 (L/ha) than spray volume or concentration.    joe_neal@ncsu.edu