Vegetative growth and sporulation of Bipolaris sorokiniana on infected leaves of Poa pratensis exposed to postemergence herbicides

Abstract

Poa pratensis was exposed to the postemergence herbicides 2,4-D, MCPP, and dicamba at concentrations of 10−6 M applied to the soil surface. The four youngest leaf blades were inoculated with Bipolaris sorokiniana and subsequently detached to determine the effect of the herbicides on vegetative hyphal growth and sporulation on the leaf-blade tissue. Hyphal growth from infected leaf disks cut from detached leaves was stimulated by 2,4-D and dicamba. MCPP did not affect hyphal growth. All herbicides increased sporulation by B. sorokiniana on the detached leaves. Increases in sporulation did not differ between 2,4-D and MCPP. Dicamba induced the heaviest sporulation on leaf blades. Key words: dicamba, MCPP, mecoprop, 2-methoxy-3,6-dichlorobenzoic acid, 2(2-methyl-4-chlorophenoxy)propionic acid, 2,4-dichlorophenoxyacetic acid.