Factors Influencing the Biocontrol of Tumble Pigweed (Amaranthus albus) with Aposphaeria amaranthi. A. S. Mintz, Graduate Assistant, Department of Plant Pathology, University of Arkansas, Fayetteville 72701. D. K. Heiny, and G. J. Weidemann. Research Associate, and Associate Professor, Department of Plant Pathology, University of Arkansas, Fayetteville 72701. Plant Dis. 76:267-269. Accepted for publication 20 September 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0267.

Growth chamber studies and field tests were conducted to evaluate Aposphaeria amaranthi as a potential mycoherbicide for tumble pigweed (Amaranthus albus). Seedlings in growth chamber studies were killed within 2 days after inoculation with 1 × 10⁶ conidia per milliliter and an 8-hr dew period at 28 C. The onset of dew could be delayed for 72 hr postinoculation without an apparent decrease in disease severity. Inoculations with conidial concentrations as low as 1 × 10⁴/ml were sufficient for plant death when followed by a 24-hr dew period. Dew temperatures from 20 to 28 C were conducive for disease development. In field tests, 99% of seedlings with two to six true leaves were killed when sprayed to runoff with 6 × 10⁶ conidia per milliliter. Results from these studies suggest that A. amaranthi may have potential as a mycoherbicide for tumble pigweed.

Keyword(s): bioherbicide.