Why Lawns Develop Fungal Disease
There are many reasons why a lawn may develop a fungal disease:
Fungi spores exist everywhere, like bacteria’s and viruses. There are many types of fungus; they are spread everywhere by the wind and rain; without human intervention. Fungi spore presence is not harmful to the lawn, unless it turns into a disease. Normally, spores are located in the thatch of the lawn clippings. This is why we use mowers with grass catchers and we take the clippings with us in order to not increase this layer of debris; although it is impossible to collect everything we mow. We recommend dethatching of the lawn at least every 2 years; but, it is not always absolutely necessary. Each type of turf grass is susceptible to some specific fungus, so correct identification and diagnosis is needed prior to any treatment.
Fungal disease develops when hot weather, humidity, and a heat stressed lawn create the best conditions for these spores to become highly active; multiplying, propagating, and infesting a considerable area. This is why most fungal problems happen during the hot weather season; the fungi is inactive (dormant) during cold weather. Rain water or mechanical watering is also a way to transport and spread the spores; although, the main intention is to irrigate the lawn and it is the only way to provide water to plants. Unbalanced presence of lawn nutrients (nitrogen, phosphorus, potassium) is also a factor that aids in development of the disease; and for this reason we have an annual schedule for fertilization to keep enough and the right amount of nutrients during the entire growing season and a yearly soil test also helps checks this.
Because of micro climate conditions (different small weather conditions in one lawn), it is possible to have the presence of fungal disease in one part of the lawn and the rest of it can be perfectly healthy. This is why we recommend treatment for the entire lawn once we notice the disease in any significant area of the lawn. This way we avoid its propagation. Also, if a home owner treats its lawn with fungicides, but other neighbors do not; the chances of contamination are increased knowing that wind and rain transport spores from one place to another.
Mowers help to avoid the developing of the disease when clippings are collected; but, also can spread the disease by being transported on the blades, spores from one infested lawn to another one without the infestation already manifested; this is called cross contamination. There is really no way to find out how much of the fungus developed in a lawn was transported there my mowers. However, to avoid being agents of the problem, if we know there is an infested lawn, we mow it last in that route; and the machines are pressure washed once we return to the shop on a daily basis.
Fungicides kill the disease but they never get rid of 100% of the spores; it just keeps them under control by reducing their number to the minimum acceptable. But spores multiply, so this is why we need to keep a barrier of chemicals to avoid its propagation. Fungicide treatment lasts no longer than 4 weeks; therefore, we recommend 3 to 6 applications during the growing season. Fungicides are not harmful to people or pets; however, we recommend to avoid the lawn the day the application is applied for a minimum of 2 hours to allow for dry time.
The only way to avoid infestation is the use of preventative applications. Due to the additional costs of preventative treatment, some customers choose to only treat when the disease is noticeable. It is fair to say that the weather could be very favorable for a healthy lawn one year without the application of fungicides; so we do not want our customers to think they are spending money without it being necessary to do so.