Cleansing By Fire
By Dana Borglum
Every bloom season Sylvia and I host 1000+ iris lovers or potential such. Invariably, someone complains about iris borer problems and asks how we control it with so many plants. Years ago the problem was beginning to concern me. So it was with great interest that I read Allan Ensmingerís article in the Bulletin of the American Iris Society about burning old leaves to control borer. Ever since that time, maybe some 12-15 years now, I have to some extent Ďburnedí over the beds where applicable. And, it works very well, even though at times it can also be difficult.
There is in my mind, no doubt that burning keeps borer to a reasonable level. Total control is a pipe dream and unreasonable to expect. In 2002 we dug, divided and reset some 7000 rhizomes. In dividing and trimming for replanting, we found less than 10 infected plants, all bearded iris, none in beardless, albeit they are harder to see in beardless iris. Ever since I sent Carol Warner a nice, big, healthy worm to her consternation, Iíve kept Siberians burned off each spring.
To get good burn in Siberian iris, the old leaves need to be raked up off the wet ground on a dry day, say in the morning, and then burned off in the afternoon. If leaves havenít been cut off the fall before, there can be quite a blaze, sometimes roaring down the row seemingly out of control. This scared me the first time I tried the burning experience. I couldnít see how any plant could survive such heat. However, the heat goes up, not down against the plant. I do like to practice my burning event in March (for here in central New York and USDA zone 5a/b) before the plant starts to grow and the new leaves donít get scorched. It doesnít hurt the plant so much as it looks bad, especially if theyíre to be dug for shipping in the spring.
The problem with fire is that it doesnít care what it burns. Plant markers are very apt to be ruined and need replacing if not removed first. Also, always be sure the fire isnít able to jump to any other place and get out of control. If such a situation exists, a water hose is necessary, which is a good idea anyway. We live on a farm so burning is an accepted practice, but many growers have laws against such. You should be sure of the laws in your area before trying to burn your own plant bed(s). Cutting the leaves in the fall and then burning in the spring works very well for us and keeps things down to a dull roar. Tall Bearded leaves are harder to burn, but the heat fills the borer eggs even if the blackened leaves are still there.
We donít stop there for borer protection however. When the plants are up 6-8" or we have a few warm days in a row, we spray with Cygon. Two (2) treatments of a spray mix before bloom completes the program. Along with Cygon, we mix in a fungicide for leaf spot and Epsom Salt for the magnesium.
The rest of the iris growth process we leave to the Lord. In Malachi 3: 8-12 the Lord asks us to test Him, the only place in the Bible where we are told that. If we will tithe like we ought, He will give back more than we gave and keep pests out of our crops, vs. 11. Sylvia and I feel this is more powerful than anything else we can do for our iris and we think results bear this out. Try it, youíll like it.