The Potential of Stagonospora sp. as a Mycoherbicide for Field Bindweed

Abstract

Field bindweed ( Convolvulus arvensis L.) is one of the 12 most important weeds worldwide. Stagonospora sp. Isolate LA39 was isolated from diseased field bindweed plants collected in Europe. No crop tested was susceptible to the fungus, but disease symptoms were observed on other Convolvulaceae species. On field bindweed, the fungus induces disease symptoms (i.e. lesions) mainly on leaves and less severely on stems. The application of spores in an oil emulsion (10% oil in water) enhanced the disease on field bindweed plants compared with spores suspended in a 0.1% aqueous solution of the surfactant agent, Tween 80. The necrotic leaf area of inoculated plants increased as the length of exposure to 100% relative humidity (RH) and the spore density applied increased. Severe disease developed on plants inoculated with 1 107 spores/ml in oil emulsion, even in the absence of exposure to 100% RH. A delay of exposure to 100% RH (up to 8 h) did not have a significant eVect on disease severity. Field bindweed was susceptible to the fungus at all growth stages tested, but older plants were more susceptible than younger ones. It was concluded that isolate LA39 has potential as a biocontrol agent of field bindweed, especially when applied in an oil emulsion. The oil emulsion maintains the aggressiveness of the pathogen during a dew-free period and provides a favourable microenvironment during the infection process.