Does the use of broad spectrum systemic fungicides have a negative effect on arbuscular mycorrhizal populations? Looking at the picture on the side of a box of a Bayer product I was struck by how the product claimed to clean the root system... but that would be bad most of the time, possibly. Is this stuff like "plant chemotherapy", to be used only in the most grave of circumstances? Do any of our contributors use the stuff regularly, and if so which one? Musing on the approach to treat blackening bark on an A. pensylvanicum. If I cut there will be nothing left. -E
Hmmm, never thought about this before. Interested in finding out the answer from those that know more than I. I've used the Bayer 3 in 1 (fungicide/insecticide/mites) twice this fall/winter as a preventative, and just sprayed them all with horticultural oil last week... Hopefully this was the right thing to do!
Mycorrhizae is a type of mycelium. And mycelium is a fungus. I would guess that a system fungicide would not be good for any kind of mycelium. I try to stay away from systemic fungicides. I think they are pretty bad stuff. Have you heard about some of the honey bee theories involving Bayer products? For psuedomonas you could try a copper spray in the winter or a biofungicide like serenade in the spring time.
I have found that the Bayer product in both granular and water-in systemic types tend to be very expensive. The few benefits are outweighed by the cost and possible risks. I no longer use them on my maples, but did in the very early days of collecting. Although it did clear up some black spots on leaves and bark for Sango kaku and orange dream, it was not effective at all for aphids. I think the product may have taken credit for what may have cleared up on its own, because I believe the problems were associated from the growing conditions at the nursery that were corrected when I planted the trees at home. The 3 in 1 spray will cause permanent spotting on the leaves, so I do not use it at all anymore on my maples during the growing season. Some varieties may stand up to it better than others, but I am not willing to take the chance. I do find it works well on my junipers, so I do keep in on hand. Many of my growing season problems have been corrected by the dormant season treatments like copper spray and lime sulfur spray (lime sulfur also enhances the grey /silver bark color on some varieties like atrolineare). With aphids, I kill the ants that farm and introduce them to a tree in the spring. I use my fingers to smash the aphids on Sango kaku and bonfire. Out of my 45 maples those are the only two trees that aphids seem to like, so a little bit of persistence in the first few weeks of the growing season fixes what would otherwise be a season long problem.
Mycorrhizae is the interaction, fungi that participate in this interaction are called mycorrhizal fungi.
Not meaning to single out Bayer products specifically, the question applies to any systemic fungicide, I suppose. We've sometimes talked about the inadvisability of fungicidal soil drenches. Although I have been advised by a nursery to use Aliette drench (Fosetyl-Al) against what might have been phytopthora attacking roots. But I don't recall talking about foliarly applied systemic fungicide. -E
I definitely wouldn't subject the soil system to a toxic drench in response to a condition that might be present.
