Hi All,

Ted Petit here in North Florida. As most of you know, I rarely post the Robin. But, I have had some rather serious observations and thoughts on rust lately that I thought I would share with you. This will be somewhat of a long post, but I think it is serious enough to make it worth your while to read.

When it became clear that rust was spreading, we began an aggressive preventative spray program to keep it out of our garden. We have no choice since we owe it to our customers to ship out disease free plants. This is true of all major hybridizing gardens, which makes it impossible to make objective observations about the problem and its ultimate solution.

However, friends of mine that live about 30 miles away have a large daylily garden that showed signs of rust in late spring. I will not mention their names on the Robin, but some of the Florida gardens know them as Ted's friends that own the big cattle dairy. They hybridize about 20,000 seedlings a year, so they have lots of daylilies, including many of the newest and most expensive. But, since they have not yet introduced anything, they do not sell plants, and therefore, did not have to deal with the Florida Dept. of Agriculture. Since they were so busy with the dairy, they decided not to spray for rust, instead just let it run its course. I have watched the progression of rust in their garden without any sprays, and several things seem clear.

I do not wish to sound like an expert here, and would appreciate feedback from others who have had a chance to observe rust firsthand. But the following seemed reasonably obvious:

1. The Worst Is Not That Bad: Without any spraying, the worst-case scenario is not that bad. At first they talked about spraying eventually, when they found some time. However, I visited their their place yesterday. When I got there, I said I stopped by to see how the rust was doing. Their response was that it was going away. I carefully looked at the plants. For some reason, on most plants the rust had stopped spreading to the new leaves; the new growth was healthy and showed no sign of rust. The ugly spots on the old leaves had turned black and looked as if the rust had died. I am not sure why this has happened, but it may relate to the summer heat. I have heard both that the rust should be worst in the heat, as well as reports that the rust can not tolerate the heat and will be worst in cooler weather. I have no answer here.

   Also, while some plants looked seriously weakened, most of them seemed OK. It looked like leaf streak, clearly effecting the cosmetics of the older leaves, but nothing that seemed to do any real harm to the plant. In general, I don't think the average backyard gardener would think much of it, other than the plants looked a bit beaten up by something. For a while, I had been feeling somewhat depressed about the whole rust thing, but having seen it completely untreated, I left feeling quite relieved. Left on its own, it is really not all that bad on most plants.
    

2. There Are Large Differences in Susceptibility: Some plants seemed to be completely resistant to rust, most show some degree of susceptibility, a few are very prone to it and are clearly harmed. The most susceptible plants look like the ones on the Internet pictures. There is no question that any gardener would see these as very sick plants, and not want them in their garden. The vast majority of the plants, however, only showed some damage on the leaves from the rust, but the plants overall looked OK, and had beautiful flowers. Some plants growing in the middle of infected ones for months showed very, very little rust... you had to look closely to find a few little spots. I even found a few named cultivars that showed absolutely no evidence of rust.... apparently complete rust resistance.
    
3. Susceptibility May Be Related To Susceptiblity to other Fungal Infections: While I was not able to do a complete scientific examination, it appeared that those plants that were most susceptible to rust were also those that I know are also most susceptible to leaf streak and crown rot. While we do not always talk about these things, those of us that run large commercial gardens eventually learn which plants are susceptible to other fungi. Those same plants also appeared to be the hardest hit by rust.
    
4. Susceptibility Appears to be Genetically Transferred: Certain lines appear to be rust susceptible. There are some plants that are either siblings to other introduced cultivars, or are kids from them. There are certain lines (and I will not state which ones here) that are very susceptible to rust, while others are not. There was a very high correlation between rust susceptibility of sibling and kids of rust susceptible plants.

   Interestingly, I received a phone call from a grower in Central Florida today who found that those same lines were also some of the most highly Rust susceptible plants in her garden. Further, in looking at their seedling field, there would be a run of plants that were rust susceptible, but the rust stopped at the marker that marked the next cross. When we looked at the most rust prone plants, and went back and looked at the parents, the following seemed clear. If you cross two rust prone plants, the kids will likely be very rust prone. Kids from two rust resistant plants were also rust resistant.
    

5. Rust Prone Plants Infect Less Prone Plants: While many plants are reasonably rust resistant, it is difficult for them if they are right beside a highly infected plant that is constantly covering it with spores. After talking to several others, it seems that even a small amount of spraying controls rust on most plants that are reasonably resistant. However, the very rust prone plants act like a magnet for rust, and spread the spores. Culling the most rust prone plants from the garden will probably do a lot to help the others fight it off, prevent reinfestation, and limit the amount of spraying for those that choose to spray.
    
6. Thoughts on the Future: Those are my observations, what follows are just my thoughts. First of all, I am very relieved to see that this rust will clearly not destroy the daylily or the world that has built up around it. Some people will clearly choose to spray to keep their gardens pristine. Others will not care, just as they ignore unsightly leaves on many other garden plants. Rust does not kill most daylilies, or even cause major harm on most of them. Leaf streak does not do-in the daylily, and neither will rust.

Clearly, the most important long-term action is to hybridize only rust resistant plants to breed rust out of the daylily. This is probably the most important challenge ever faced by daylily hybridizers since Stout started making the first crosses. The problem is that no large hybridizing and commercial garden can stop spraying since they do not want to spread rust. Herein lies the problem. The hybridizers cannot selectively breed for rust resistant plants if they are not allowed to have rust to find out which ones are resistant. The obvious course of action would be to stop spraying, cull the rust prone plants, and breed with the most resistant ones. But if you cannot have rust in the garden to test for resistance, how can you move forward?

I think that there are two possible answers.

1. Find a "Rust Test Garden". Many of the Florida hybridizers, myself included, have a "Northern Test Garden" to test for cold hardiness of their plants. When I hear that one of my plants will not survive in a cold climate, I stop breeding with it. Now, thanks to my friends with the dairy, I have a Rust Test Garden. I have agreed to guest one of each of my very best future seedlings with them as long as they continue not to spray. This way, I will find out which cultivars are resistant and which are prone. From my notes already, there will be a number of my own lines as well as lines of other hybridizers that I will no longer be breeding with because they are very rust prone. I have also been very busy digging up and composting rust prone plants from my own garden so that I will not be tempted to breed with them next year.
2. The second possibility for finding out rust resistant plants, if you cannot have a rust test garden, is to rely on information gathered from this robin. For my own personal garden, I have several goals. I plan to at least try to breed rust resistance into my lines. Over the course of the next several years, I hope to be able to separate my seedling field from my sales garden, and stop spraying in the seedling fields. By only selecting reasonably rust resistant plants, we might be able to (at least hope) to stop spraying in 3 years. While this might be overly optimistic, I think it is do-able. I have spoken to some other hybridizers that feel the same way. Eventually, it would be nice to also be able to indicate rust resistance in the plant descriptions of new introductions.

Pat Stamile's double "Over the Top" had only a small amount of rust, and seemed to be very resistant. I will be using it heavily next year. I could not find a single rust spot on my own Burning Embers (this is not commercial, since I am sold out of it), Salter's Fairest of them All seemed very resistant, and an Ohio grower says that Peat's Spoons for Escargot is rust resistant (again, John is sold out of this one). I don't presently own all of those cultivars, but you can bet I will soon, and will be breeding heavily with them next year.

So, now it is up to you. Let's try to focus on the positive, and move forward. As Winston Churchill once said, "the only thing we have to fear is fear itself". If we can all help out here, this will soon be a bad memory.

Warm Regards,
Ted L. Petit
Le Petit Jardin
McIntosh, FL & Toronto, Canada