Rust Disease – 2013

The 2013 rust disease outbreak seems to have arrived a little earlier than usual.  My thoughts about the current rust epidemic are intended for lawn care professionals, who must address reasonable questions from their clients.  Most professionals are very familiar with the basics of rust disease.  To briefly review from the 2013 perspective--the ample precipitation favors dispersal of rust spores and subsequent infection of susceptible turf.  The disease is largely cosmetic, but the orange spores that are easily dislodged from leaf surfaces can be more than a nuisance, covering shoes, pets, and lawn mowers with a rusty residue.  New spring-seeded lawns that lose vigor during heat and drought conditions of summer may be severely damaged by rust.

One question about rust is asked more than any other—Will it harm my dog?  The answer is no…and no further explanation is necessary.

Another question frequently asked is – If I collect my clippings after mowing, will the disease disappear?  The answer here is “no” also.  There are tens of millions of rust spores in the air--inoculating your lawn every day.  Also, because the rust pathogen must complete every stage of its life cycle on a LIVING host, spores on your clipped grass blades will soon die, and no longer be a threat to the yard.

A final question regards control—both long and short term. 

If the lawn is in need of any kind of renovation, now is the time to consider Kentucky bluegrass cultivars with rust resistance.  Many of the newest cultivars are only slightly affected by the rust pathogen.  Local lawn care professionals or garden stores will have access to information about rust-resistant grass.

Keeping the grass healthy with water, fertilizer, and regular mowing normally will keep rust at bay.  This year seems to be a little different, maybe because of all the rain, and the fact that nutrition is a little low at this time of year.  Suggest trying the fertilizer route first.  Applying the equivalent of 0.2 lb N per acre may do the trick.  Be prepared to resume mowing if the rain continues, and do not apply if the 3-4 day forecast includes daily high temperatures in the 90’s.

The final approach is chemical.  There are excellent fungicides available that will shut down a rust outbreak in less than a week.  The DMI and QoI  (strobilurin) fungicides are very effective against rust but, on well-established turf, should be considered only as a remedial treatment.  On newly seeded stands, fungicides should be applied at the first sign of disease.  In most cases, outbreaks will be quelled with a single application of an effective fungicide combined with efforts to encourage turf growth.

For more about rust disease, access the Purdue Turf Program website and click on “publications”.  In that list, you will find BP-110W  “Rust Disease”. 

Dr. Rick Latin, Professor of Plant Pathology