Turfgrass disease expert Dr Percy Wong outlines some of the new ERI diseases present in Australia, the fungal pathogens that cause them and possible strategies to manage them in various turf situations.
In the last 20 years, there has been an upsurge in the prevalence and severity of patch diseases in warm-season grasses such as couch, kikuyu and buffalo, as well as cool-season grasses such as bentgrass and wintergrass.
These patch diseases, often called ERI diseases, have been very worrying for turf managers because they have not always responded to chemical control. The most likely reason for this is that the diseases have been misdiagnosed and, therefore, the chemicals used would have been ineffective. My research has shown that the majority of these diseases are new and some of the fungal pathogens that cause them do not even have scientific names at present.
We hear a lot about ‘ERI fungi’ these days but what exactly does the term mean? ‘ERI fungi’ stands for ‘ectotrophic root-infecting fungi’ (Clarke and Gould 1993) and is a catch-all name given to fungi which cause a number of root diseases in turf.
These soil-borne fungi produce black mycelium (fungal threads) on the surface of roots and underground stems, before invading the plant tissues and causing death of roots and underground stems (see photo). They include;
Such diverse fungi and well-known pathogens as the take-all fungus (Gaeumannomyces graminis var. avenae), spring dead patch fungus (Ophiosphaerella namari) and, in the USA, the summer patch fungus (Magnaporthiopsis poae) (Smiley et al. 2005);
As such, it would not be possible to specifically control ERI fungi as a group with certain chemicals without first identifying the exact pathogen or pathogens present, since the control measures are different for different pathogens.
For example, Bayfidan works well against take-all patch but not against spring dead patch.
Therefore, more research needs to be carried out to devise management strategies for the control of each of the ERI fungi. Chemical companies would also need to test their new chemicals against each of these pathogens in order to make useful and effective recommendations. To have a label saying a chemical is effective against ‘ERI fungi’ is meaningless because, as we have noted above, the pathogens are so varied.
Summer decline on a couch golf green
What follows is a summary of some of the ERI patch diseases currently present in warm-season grasses and cool-season grasses in Australia, the fungal pathogens that cause them and notes on possible management strategies.