OUT, BLACK SPOT, OUT — DEALING WITH PERSISTENT POPLAR PROBLEM
Q We have very large poplar trees in the park right across from our house. I usually spread a liberal amount of dead leaves over my perennial beds late fall for winter protection.
This year the trees started shedding their leaves in early September already with many leaves almost black in colour instead of the usual golden yellow. Tiny, raised black dots cover the backs of the leaves. Is this due to aphids?
I had those on the leaves of my sunflower plants and those leaves also turned black. Or is it a fungus of some kind?
Now that I am raking the poplar leaves from my lawn, I question whether I should spread them over my perennial beds this year. I don't want disease or pests to hibernate.
Or would everything die off during our cold winter?
A When it comes to plant diseases, who better to ask than my retired plant pathologist friend Ieuan Evans. I don't think I have stumped him in all the years we have known each other.
Here is a reply to your question: “The black spots are a fungus disease but they will not affect anything except poplar.
The fungus helps break down the poplar leaves into compost that's good for the garden.”
Q Two years ago we thought we would lose our Swedish Aspen. We had lost one because of those wood-boring insects. You suggested Dr. Doom residual spray and the nice thing about it is that it has a nozzle that is injected into the tree. And it worked.
This spring our neighbour was at his wit's end trying to save his trees. He lost one very mature tree and one two-yearold tree to these insects. He didn't know what to do until we were able to tell him about your advice.
Our problem now is our Goodland apple tree. We put on
four red balls to discourage the pests to no avail. As of today, we have thrown away about 200 pounds of apples picked up off the ground.
We have an enormous amount of leaves. What can we do to get rid of all those leaves if this is our problem, and also do the apples fall because of the insect invasion? We are at our wit's end and will probably have to spray the tree next spring. Any suggestions?
A I am so pleased that the advice is working for you on your Aspen tree.
I believe the problem you are referring to in your question is apple maggots and there is still no chemical control for this issue. The bait system with the balls you mentioned is the go-to method but there are a few tips:
It is critical to start control early. You should be hanging the traps in mid-may. The adults usually emerge from the ground in Alberta around May 25.
Check the traps from mid-june to harvest and do this two or three times a week. If the traps are full of insects, you may have to reapply the special glue you applied on the balls. You want to be trapping as many adults as possible. Egg-laying activity begins in July and carries on until August.
If your neighbours are also growing apple trees they, too, will have to set out traps. This has to be a co-ordinated effort by the neighbourhood.
Ensure that all fallen fruit is picked up daily until no fruit remains.
In late fall use Remay cloth placed on the soil under the tree. This woven material can help prevent adults from emerging from the soil next spring.
Yes, the fruit is likely dropping because of the damage done by the insects. There is no spray available, so continuing to use the bait traps is the only thing you can do.