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

Poa pratensis was exposed to the postemergence herbicides 2,4-D, MCPP, and dicamba at concentrations of 10 super(-6) M applied to the soil surface. Sequentially older leaf blades were inoculated with Bipolaris sorokiniana and detached to determine the effect of the herbicides on saprophytic hyphal growth and sporulation on the tissue of each older leaf. 2,4-D and dicamba stimulated hyphal growth in vitro from leaf tissue of all ages; MCPP had no effect on hyphal growth. All herbicides increased sporulation by B. sorokiniana on leaf tissue of all ages. Both hyphal growth and sporulation increased progressively on tissue from sequentially older leaves of P. pratensis exposed to dicamba.