First Report of Dicyma pulvinata on Epichloë typhina and Its Potential for Control of E. typhina

Abstract

The hyperparasite Dicyma pulvinata is reported for the first time on Epichloë typhina, which causes choke disease in orchardgrass seed production fields in the Willamette Valley, OR. In an orchardgrass field near Corvallis, OR, D. pulvinata was found on 7% of E. typhina stromata. Infected stromata had fewer perithecia and appeared shrunken, desiccated, and pale gray to grayish-white, in contrast to the orange colored noninfected stromata with mature perithecia. In greenhouse inoculations, D. pulvinata significantly (P < 0.05) reduced perithecial formation on E. typhina. However, under field conditions, a significant (P < 0.05) reduction in perithecial development occurred in one trial initiated in mid-May, but not in a second trial initiated in early June, although D. pulvinata sporulated on 92% of the inoculated stromata from each trial within 72 h after their incubation in moist chambers. Under field conditions, D. pulvinata may have potential as a biocontrol agent of E. typhina if applied when stromata start to emerge during mid late April to early May when rain and high humidity conditions are typical. However, development of D. pulvinata would likely be limited by low humidity conditions that often occur during mid- to late June in the Willamette Valley. There are currently no effective chemical or cultural controls for choke in orchardgrass. Accepted for publication 3 November 2009. Published 16 February 2010.