Control of Winged Waterprimrose (Jussiaea decurrens) and Northern Jointvetch (Aeschynomene virginica) with Fungal Pathogens

An indigenous, host-specific, pathogenic fungus that parasitizes winged waterprimrose [Jussiaea decurrens (Walt.) DC.] is endemic in the rice growing region of Arkansas. The fungus was isolated and identified as Colletotrichum gloeosporioides (Penz.) Sacc. f. sp. jussiaeae (CGJ). It is highly specific for parasitism of winged waterprimrose and not parasitic on creeping waterprimrose (J. repens L. var. glabrescens Ktze.), rice (Oryza sativa L.), soybeans [Glycine max (L.) Merr.], cotton (Gossypium hirsutum L.), or 4 other crops and 13 other weeds. The fungus was physiologically distinct from C. gloeosporioides (Penz.) Sacc. f. sp. aeschynomene (CGA), an endemic anthracnose pathogen of northern jointvetch [Aeschynomene virginica (L.) B.S.P.], as indicated by cross inoculations of both weeds. Culture in the laboratory and inoculation of winged waterprimrose in greenhouse, growth chamber and field experiments indicated that the pathogen was stable, specific, and virulent in a wide range of environments. The pathogen yielded large quantities of spores in liquid culture. It is suitable for control of winged waterprimrose. Winged waterprimrose and northern jointvetch were controlled in greenhouse and field tests by application of spore mixtures of CGJ and CGA at concentrations of 1 to 2 million spores/ml of each fungus in 94 L/ha of water; the fungi did not damage rice or nontarget crops.