I know there
has been a lot of excitement over the Giants winning the World Series, but the
fact that some lawns are turning orange really has nothing to do with
baseball. The grass may exhibit some
yellow spotting initially, but as the rust advances one will see a
reddish-orange powder develop on the leaf surface. These are the spores of a lawn infecting
fungus (Puccinia sp.). Mowers, shoes and clothing can become a
magnet for picking up the rust colored spores as they pass across the infected
lawn transferring the spores to other lawns that may be susceptible, especially
if there is a bluegrass component to the lawn mix. If you pass your fingers across the leaf
blade you will likely have the orange spores deposited on your skin. It will not hurt you…really.
The rust
colored lawns tells me a few things.
First, there is likely some Kentucky bluegrass in the lawn as that is
the most likely grass type to get rust.
Ryegrass and tall fescue may exhibit some rust in rare cases here in
Central California. Secondly, rust
indicates that the weather has changed and we are in a period where the days
are warm (70 to 75 F) and nights are getting cooler and damper. Spore germination and infection of the rust
fungus into host plants can occur with extended periods of leaf moisture
lasting 10-12 hours from dew and/or irrigation. Other conditions like lack of water, low
levels of nitrogen, infrequent mowing, and mowing too short can certainly
enhance the presence as well. Rust was
noted on lawns November through June this last year, but the peak occurrence
was mid March and the month of April.
Although it
can be very visible and a bit unsightly, the disease rarely causes any notable
damage to the lawn. Application of a fungicide
is not usually recommended when proper cultural practices are employed. I would be sure that the lawn has been
adequately fed with a fertilizer that will promote new growth thus allowing the
infected leaves to be cut and removed.
Secondly, I would make sure the lawn has sufficient water available to
favor good growth and water in the early morning so that the period of wetness
does not get extended further into the day.
Finally, I would make sure that the lawn is mowed weekly at 2.5 inches
or higher.
I am told before by Atlanta Lawn Treatment expert who visited my lawn that being rusty of the grass is caused by fungi or a disease. But I never have thought that this fungi or disease can be transferred to other plants by simply walking on it. If this is the case, it really must be cured and prevented so that other grass plants will not be infected.
ReplyDeleteI do not lose sleep over rust here in central California as it only occurs for a month or so and goes away with a good fertilization and regular watering and mowing, and we pretty much only see it on the bluegrass portion of the lawn. Occasionally we will spray a fungicide if we want quicker or longer lasting results. The rust needs a susceptible host plant and favorable weather conditions to allow new infections. You are right that it can spread and that proper fertilization along with regular mowing will help reduce the incidence of the fungus. A fast growing lawn will not usually have a significant level of infection. It is the slow, stagnant growth pattern during heavy dew periods that will set it off. Prevention and early cure is the best approach. I would try fertilization first and give it 2-3 weeks to see if the new growth is clean and the infected growth has been mowed off.
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