She asked, “What’s wrong with my plants? Should I spray them with liquid Sevin?” We walked out to look at the leaves on the viburnum Davidii that lined one of the planting beds.
I said, “Liquid Sevin won’t help you here because it is an insecticide. The problem with these plants is not insect related but is fungus related instead.” I pointed to the holes in the leaves. “These are a sign of a fungus disease that is called ‘shot holes.’ The problem starts as a spot on the leaf and then grows outward in concentric circles. As the spot on the leaf kills the plant cells, it ends up looking like a hole that has been eaten by a worm or an insect. The dark brown end of the other leaf in the picture is a sign of another kind of fungus.”
We started walking around and looking at other plants. Some of the leaves on the dragon wing begonias were looking funny. The spots are fungus related as are the curly leaves. You will also notice a browning on the margins of the leaves.
The hosta plants are showing a lot of fungal damage. Some of this damage may be from getting too much sun, or the abundance of sun and the fungus are working together. The fungus attacks any weak spot in the leaf.
I frequently see the damage pictured below in acuba. Again, I think some of it is light related, but it seems to be mostly a fungus infection.
Here is fungus damage on a Knockout rose. Note the holes in the leaves and the damage on the leaf margins.
Paige and I discussed the fact that when something goes wrong with a plant, our first reaction is to water it more. Since fungus problems are moisture related diseases, this is the totally wrong thing to do. The begonia pictured below is a prime example of a plant that has been over watered. The leaves drop off or become spotted. The leaf margins die back, and there may be some kind or other of a powdery mildew that will attack the flowers.
Below is a plant that is probably beyond repair. One of the types of fungus is called ‘stem rot’ and is soil borne. This picture shows over- watering in its extremity.
I don’t know enough about the different names or kinds of fungi to be able to go into the subject and I don’t really think it is necessary. The main point is to be able to recognize a problem as fungus related instead of insect or otherwise related. The concept is the important thing.
Paige asked, “So how do I tell fungus damage from insect damage?” I replied, “If you just start looking at the problems you will see the difference. I have given you the concept and I define a concept as a collection of questions that I have never asked before.”
You can treat fungus problems on your plants. There are a number of fungicides on the market that will work. I am currently using Daconyl which gives me very good results. I think that one should have two different fungicides and alternate them. Sometimes one fungicide will kill a type of predatory fungus that works against another kind of fungus.
Your favorite nurseryman should have several kinds of fungicides to choose from. One of the best fungicides that I have found is Cleary’s 3336. This fungicide is systemic and helps control all sorts of fungus diseases, even going through the plant to reach the roots. You may find it at BT Grower’s supply online.
One of the things I like about Paige is that she asks well thought out questions—lots of them. When I told her that the fungus treatment would not get rid of the damage that had already occurred, but would prevent the damage from becoming worse, she asked, “Should one wait until the damage shows up, or should one spray to prevent the damage?”
I replied, “It is best to be proactive, but later is better than not at all.”
In the nurseries and greenhouses that produce our ornamental plants, the grower will maintain a strict fungicide program. I think that in your yard, it is satisfactory to be able to recognize the problem when it shows up. I also believe that if one were to spray the ornamentals about once a month with a fungicide, the quality of growth would improve greatly.
Insecticide kills insects
Fungicide kills fungus.
You can decrease plant fungus problems by watering in the morning instead of at night.
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