Biological control of hedge bindweed (Calystegia sepium) with Stagonosporaconvolvuli strain LA39 in combination with competition from red clover (Trifolium pratense)

In a maize cropping system where a living green cover suppresses many weeds , Calystegia sepium is able to escape control. In this paper we report the potential for biological control of C. sepium by using the bindweed pathoge n Stagonospora convolvuli strain LA39 as a mycoherbicide in combination wit h competition by the green cover plant Trifolium pratense. In a greenhouse experiment, competition from shoots of T. pratense caused a strong reductio n of the biomass of C. sepium, and combined competition from shoots and roo ts had the same effect. In a second, factorial greenhouse experiment, compe tition by T. pratense again reduced C. sepium biomass. However, S. convolvu li did not influence the number of leaves or the biomass of C. sepium in th e greenhouse even though severe necrosis was observed on inoculated bindwee d leaves. In contrast, in a a-year field study, S. convolvuli caused severe disease and a strong reduction of C. sepium ground coverage in maize. Unde rseeding with T. pratense had no effect on disease severity, but T. pratens e reduced ground coverage by C. sepium at one of eight samplings in the fir st year. In conclusion, S. convolvuli is useful in the field and, as shown in the greenhouse, a competitive green cover might improve biological contr ol of C. sepium. (C) 1999 Academic Press.