Figure 2: Symptoms of etiolation associated with the bacterial pathogen, Acidovorax avenae pv. avenae. Bacterial etiolation is mostly noted on aggressively managed turf with symptoms beginning at 80 F. Research on bacterial etiolation conducted at North Carolina State University has demonstrated that etiolation can be caused by two bacterial species, A. avenae pv. avenae and Xanthomonas translucens. The effect of growth regulators on the development of the disease was found to be dependent on the pathogen causing the disease. When X. translucens is the cause of etiolation, trinexapac-ethyl reduced disease symptoms, but when A. avenae pv. avenae was the cause of etiolation, trinexapac-ethyl increased disease symptoms (Roberts et al, Page 52
2015). This point emphasizes the importance of an accurate diagnosis! Notably, the researchers found that trinexapac-ethyl improved turf quality despite etiolation symptoms (Roberts et al, 2015). Much more research is needed before conclusive recommendations concerning management of bacterial etiolation can be made. The rest of the summer was marked with the usual suspects such as dollar spot, brown patch and anthracnose until fall, when high levels of rain and wet weather resulted in an outbreak of downy mildew of turfgrass (also called yellow tuft), caused by Scleropthera macrospora.