Rust, Nasturtiums & Fire Blight on Mountain Ash

Still more questions: this time about rust on grass, growing nasturtiums, and fire blight on mountain ash trees.
by Art Drysdale
by Art Drysdale


Art Drysdale, a life-long resident of Toronto and a horticulturist well known all across Canada, is now a resident of Parksville, British Columbia on Vancouver Island, just north of Nanaimo. He has reno-vated an old home and has a new garden there. His radio gardening vignettes are heard in south-western Ontario over radio station Easy 101 FM out of Tillsonburg at 2 PM weekdays.

Art also has his own website at

August 3, 2003

At top, a close-up of the red pustules that identify rust disease on wheat OR grass, this photo courtesy Prof. J.E. Watkins of the University of Nebraska-Lincoln. Immediately above something to tease Marjorie Mikkelson, who wrote about her problem with nasturtiums--I took this photo at the Waller Seeds flower fields in California in July 1979 while touring all of the major seed producers there. May Marjorie's nasturtiums look like this once she gets them into the sun, and away from heavy fertilizer. Below is the Penstemon that a friend of Chris Chang is growing in Markham, and which came through last winter. Anybody else got ideas on this one?

Above, rose chafers devouring a rose bloom. Photo courtesy Jeff Hahn of Virginia. Below, rose chafer damage on rose bush foliage. Photo by Chris Chang.

On Monday this week Dave Woodard (affectionately known as 'Woody'), senior operator and production man at AM740 dropped me a note to say that his lawn was 'all rusty!'! I asked for more details and he said he would look more closely and report back. I told him there was definitely a disease called rust that affected grass, but that we didn't see too much of it--on grass.

Many long-time gardeners, or newer ones who have followed the re-introduction of the new Japanese barberry (Berberis thunbergii) cultivars will know at least a little about rust. Back in the mid-60s when the federal government banned all propagation and sale of Japanese barberry plants, it was ostensibly done to protect our wheat crops, and at the behest of agriculture lobbyists. You can read that whole sad story on my Website (; go to Commentaries, then the one for April, 2000.

Wheat rust (Puccinia graminis) is a very serious disease on wheat that can lead to destruction of virtually an entire crop. No less than five generations of the disease can be produced in one growing season, and in addition, there is the alternate host--deciduous common barberry (Berberis vulgaris) and Oregon grape (Mahonia). However, there is now pretty general agreement that the much-sought (for ornamental purposes) Japanese bar-berries are NOT an alternate host the way the common barberry is. Hence the recent re-introduction of new cultivars of Japanese barberries to our garden centres.

There are only a couple of good practices that homeowners with an infection of rust can carry out.

The lawn should be well fed but not over-fed. Use a high quality long-lasting chemical turf fertilizer, or consider an organic turf food such as Gaia Green Turf & Lawn Blend 6-2-3. There is some indication from re-searchers that organic fertilizers and composts may suppress and prevent the pathogens that cause disease such as wheat rust. In any case, both a starved lawn, and one that is heavily over-fertilized with chemical fertilizers, can be much more susceptible.

The disease seems to be worse during humid weather, and when there is a film of water on the grass blades. That end result alone dictates that lawn watering be carried out only early in the morning, and not at night.

If the infection recurs for a number of years then it's likely you have a very susceptible, older cultivar of blue-grass (Poa) or perennial ryegrass (Lolium perenne). The disease doesn't generally attack other genera of grasses, such as bentgrass (Agrostis) or fescues (Festuca). If this is the case you should then consider replacing all or part of the lawn with a more resistant bluegrass cultivar such as 'Fylking', 'Park' or 'Sydsport'. The oldest of the 'new generation' of bluegrasses, 'Merion' (which I used on my own lawn a way back in the late 50s), along with 'Touchdown' happen to be much more susceptible to the disease.

Unfortunately there are not now any domestically available fungicides for use on diseases such as this. There are a number of available, for example to golf course superintendents and likely to most lawn spray applicator companies. The likes of chlorothalonil, mancozeb, propiconazole or triadimefon may be available from one of those types of sources, or you may find the equivalent at lawn and garden centres in the U.S. the next time you are visiting down there. There are a number of rosarians who like to pick up a supply of one or two plant fungicides not available in Canada when they visit the U.S., so the same could be done for lawn chemicals.

Those are my only suggestions as to this very old, and perhaps most virulent of plant diseases, rust.

Meanwhile, Marjorie Mikkelsen of Virgil Ontario wrote three weeks ago about nasturtiums. Here is her question: 'I listen to your radio show as often as I can and enjoy it very much. I am trying to find info re: nasturtiums and can't seem to zero into a site that will give me specific info on this flower. I have grown these for a few years but run into the problem of fleas on the stems, and the plants becoming scraggly. I cut them back, trim off the dead leaves and flowers and have used Raid house and garden spray on the fleas, which are so bad. But I really want to salvage these three plants I am growing in containers in part shade. Any help or direction you can give would be appreciated. I also realize you probably are flooded with questions so I will understand if I don't hear from you anytime soon. Many thanks.'

Well Marjorie, first I doubt it's fleas on the stems of your nasturtiums, but quite possibly one or another type of aphid (plant lice). These come in a wide range of colours and sizes. The easy control would be one of three of the Doktor Doom products: the Botanics Plant Spray, the Home & Garden Spray, or (the longest-lasting) Residual Insecticide Spray. In your Niagara area, I believe the closest supplier would be the Home Hardware store in St. Jacobs. For other listeners and readers, they can find the nearest dealer by going to on the Web, and checking out the Dealers page.

As regards the 'scraggly' growth, there are two possible causes. First, nasturtiums love full sun so don't expect too great growth in part shade. Second, nasturtiums like poor soil, that is, soil without any great amount of fertilizer. If they have been fertilized, particularly with any high nitrogen fertilizer (i.e. 20-20-20) that would cause long, ugly growth and lack of flowering.

Good luck with your nasturtiums when you move them to full sun, Marjorie!

Chris Chang, over a month ago, sent me a batch of photos of a perennial and asked what it was. It was reasonably easy to establish that it was a beardtongue or Penstemon but from there it became very difficult. I have even stumped the experts here at The Butchart Gardens! Tom Thomson at Humber Nurseries made a tentative ID, that I'm not convinced yet is right, but his suggestion to send it to the Penstemon Society in the U.S. is a good one. I am going to ask Chris to check that out on the Web. By the way, I love the reference to 'Penstemaniacs' on their site! The URL is:

More recently, Chris wrote again, saying, 'I have another problem in the garden and I think this one is going to be easier to solve than the 'veronica' [he meant 'Penstemon'] question I posed to you a couple weeks ago. Can you identify what bug or insect is doing this damage to the leaves of my rose plant? See attached picture. Thanks, Art.'

Yes, he was right, this was much simpler. The damage is likely from rose chafers (Macrodactylus subspinosus), small (1 cm) long beetles, related to the Japanese beetle. They eat primarily the blossoms on rose bushes but also attack the foliage, leaving telltale holes in the leaves as shown in Chris�??�?�¢?? photo. Interestingly, I had little problem with these in my garden on Nesbitt Drive, but chafers were a real nuisance at the previous garden on Hopedale Avenue. The reason for that is chafers need a sandy soil in order to lay their eggs. And, the Hopedale garden was pure sand vs. the Nesbitt soil, a very heavy clay.

There is only one generation per year, and they have a relatively short lifespan of a month, and they then lay their eggs and die. So, you likely don't have to bother now about them. If you do wish to spray, any one of the three Doktor Doom products recommended earlier in this piece for aphids will work well.

Finally this week, Mike Luskey wrote about a month ago: 'Hi Art I'm asking this for my mom as she has no computer. She planted a European mountain ash in 1984. It started losing it's bark three years ago. Mom got someone to look at it and they said it has fire blight. They injected it and it seemed to prolong its life. Now it is getting worse. It looks half dead and half alive. It is losing bark and sprouting new limbs. Berries are trying to come out. Should we amputate dead limbs or just leave them. Bottom line is there any help for this decay-ing soul. Not me' the tree. I understand you are a busy man, but this is for a woman who listens to you faith-fully. Please try and get back to me. Thank you.'

Mike, sorry to be so long in replying. If in fact your mom's mountain ash did have fire blight, it is likely dead by now. My experience with mountain ash trees that get fire blight (a far more common occurrence in Western Canada than there in the east) is that they die very quickly. Literally in two or three days the entire tree turns brown. I've seen it happen to several. However, my tree man, Ian Bruce of the Bruce Tree Expert Company (, or 416-252-8769) tells me that they sometimes die over a longer period. What puzzles me, and puzzles Ian Bruce as well, is you saying that someone actually injected the tree, to prolong its life. Neither Ian no I have ever heard of that. It is possible it was injected or otherwise fertilized. That might well induce young shoots, and Ian tells me that those newer shoots are even more susceptible to fire blight, so that type of a 'fix' is really only for the very short term.

The bottom line is any dead limbs on any tree should be removed, but if your tree has fire blight, it will definitely kill the tree. I would not plant another mountain ash as a replacement. Sorry about the bad news!

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