Anthracnose is a major problem worldwide for many turfgrass managers during the summer period. Like many turfgrass diseases, its causal agent is a fungal pathogen, in this case Colletotrichum cereale.
Anthracnose affects mostly cool season turfgrass, with Poa annua being very susceptible. Anthracnose affects turfgrass in two forms: Basal rot, which as you would expect from the name affects the lower parts of the turfgrass plant – crowns, stem bases, and roots. Foliar blight is the second – and probably the more common form. Leaves and shoots discolour, having a similar appearance to drought stress in appearance. Whichever form it is, it’s important to note that Anthracnose is very much a stress related disease.
Fungicide treatments can be utilized to suppress this disease, but what I want to highlight today are the numerous management practices that can be employed to alleviate the problem when fungicides are not available or not a desirable option.
There is numerous data available on Best Management Practices to reduce Anthracnose incidence, much of it from extensive research carried out at Rutgers University in New Jersey. Anthracnose is stress-related, so any means of reducing stress will contribute to less disease – pretty much Greenkeeping 101. For example, turf managers can employ cultural practices which will have a significant impact on disease incidence. A program which includes regular lightweight rolling, sequential light topdressing, raising height of cut and judicious use of irrigation inputs have been shown to significantly reduce Anthracnose levels.
How does this work? Increased HOC equals less plant stress, which equals less disease. When taken in conjunction with regular rolling, greens speed and playability will be maintained at an acceptable level. Rolling also has supporting data showing it to have a direct suppressive action on many turf diseases, including Anthracnose. Regular light sand topdressing will protect the crowns of the turfgrasses which leads to less stress and less disease. Maintaining soil moisture levels at, for example 80% ET compared to 40% ET will also contribute to less Anthracnose.
Nutritional programs can also play a significant role in reducing Anthracnose. Spoon feeding Nitrogen, e.g. 0.1 lb/M weekly during periods of high Anthracnose pressure will reduce disease levels, as will maintaining adequate Potassium levels greater than 35 ppm. But it’s when you start combining numerous elements together in a nutritional program that you will see excellent disease suppression.
A trial I carried out in 2018 included a program which included NPK, Sulphur, Copper, Phosphite, Manganese, Zinc, Silica and Salicylic acid. Apart from enhancing turfgrass quality compared to controls, this regimen led to a significant suppression of Anthracnose to a level statistically the same as a bi-weekly fungicide treatment! A similar study running at Rutgers in NJ produced the same results.
Anthracnose can be a devastating disease on many fine turf surfaces but in the absence of fungicides it is possible to contain the problem and reduce disease levels significantly. While all the above cultural and nutritional inputs on their own will have some effect on reducing disease, it’s only when you start combining them into a regular maintenance package that you will benefit from the full effects. Think of them like pieces of a jigsaw, you get the full picture when you have all the pieces!
Dr John Dempsey
Independent Turfgrass Research
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