VIEW ARTICLE

Physiology and Biochemistry

Abolition of Selectivity of Two Mycoherbicidal Organisms and Enhanced Virulence of Avirulent Fungi by an Invert Emulsion. Z. Amsellem, Department of Plant Genetics, The Weizmann Institute of Science, Rehovot IL 76100, Israel; A. Sharon, and J. Gressel. Department of Plant Genetics, The Weizmann Institute of Science, Rehovot IL 76100, Israel. Phytopathology 81:985-988. Accepted for publication 26 April 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-985.

Mycoherbicidal preparations to selectively control weeds typically require high inoculum levels and long dew periods for establishment. The dew requirement was obviated and the inoculum threshold was reduced to one conidium per droplet when an invert emulsion was used as an adjuvant. Invert emulsion also abolished the selectivity of Alternaria cassiae and A. crassa. A. cassiae attacked eight plant species, including soybean and members of other families. The emulsion also facilitated cross-infectivity by A. crassa, a mycoherbicide specific to Datura spp., Cassia obtusifolia, and other species. Nonpathogenic fungi, such as Aspergillus nidulans and Trichoderma harzianum, colonized soybean when applied in the emulsion. Besides retaining water for spore germination, the invert emulsion may cause cuticular damage, allowing leaf penetration by the fungi. The emulsion could also suppress the plants’ elicited responses to infection.