PRUNE TREES TO STAVE OFF BLACK KNOT
Fungal disease spread by spores seems to be appearing more often in recent years
Q We have a very large chokecherry tree and it has what appears to be black knot on several branches higher up on the tree. I searched the internet and found information suggesting I should lop off the infected area. Is this the right advice, and how would I go about doing this?
A Black knot is a fungal disease that causes the cells of the plant to go into a rapid production mode. It’s a disease that seems to be more prevalent over the last several years.
This rapid cell production causes irregular swellings on some branches. These knots start off as corky, olive green in colour and they’re firm. In time they’ll turn black, hard and brittle.
They persist from year to year and expand lengthwise each year. They can swell from up to 30 centimetres (12 inches) in length and up to eight centimetres (three inches) in width.
The knots will rarely totally encircle a limb, but if there are numerous infections on several branches, this will cause a decline in the tree’s health and eventually will kill it.
The disease is spread by spores, and it can spread rapidly if the conditions are right. The fungus needs moisture to survive and spread. Rain will help spread the spores, as will overwatering the plant, or watering at night. The use of sprinklers or irrigation systems on the tree will also compound the problem.
The disease can usually be controlled through pruning. If possible, burn or bag any cuttings, and then dispose of them properly.
Q I hope you can help me with this problem. I purchased three heavy black plastic containers from Costco for a small garden in my backyard. For the past two years I have planted lettuce, carrots, beets and Swiss chard — very small amounts of each, as the containers are only about two feet wide and three feet long, and about three feet deep. Both years the vegetables have come up nicely, and then the leaves start to look burnt and stop growing. The carrots are stunted, and by the end of August, they’re no more than two inches long, while the beets are non-existent. Swiss chard grew about two inches high, then the leaves became brown and stopped growing. Lettuce got to about three or four inches and grew no more. Our yard is north-facing and we do have big trees for shade, but the boxes get great sun in the morning from the east until around 2 p.m. The boxes are watered regularly. I started with fresh dirt, mixed with peat moss and manure, with more black dirt mixed in last year. I’m not sure why the plants stop growing and seem burnt. I don’t water with a fertilizer on vegetables. Any help would be appreciated.
A My first thought is that the problem might be with the soil or the manure.
I would start from scratch with a fresh, good-quality soil specifically for containers. Adding some rotted manure to the mix is a good idea, but I wouldn’t add peat moss. It increases the acidity of the soil.
When adding the manure, the mix should be three parts soil to one part manure. The problem may indeed be too much manure, which is causing the burning. Also, make sure it’s well rotted, as green manure can cause burning as well.
The other possibility is drainage. Do you have drain holes in the containers? If not, then you need to make some before adding the new soil. Improper drainage can create the problems you have described.
Do not overwater the containers. Stick your finger in the soil up to the second knuckle. If the soil feels dry, then water. If it doesn’t then leave it for another day or so.