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Apple Maggots *& Thornless Blackberries

It sounds as if Murray has an apple maggot problem; and yes you can grow either thorny or thornless blackberries in Toronto!
by Art Drysdale
by Art Drysdale


Art Drysdale, a life-long resident of Toronto and a horticulturist well known all across Canada, is now a resident of Parksville, British Columbia on Vancouver Island, just north of Nanaimo. He has reno-vated an old home and has a new garden there. His radio gardening vignettes are heard in south-western Ontario over radio station Easy 101 FM out of Tillsonburg at 2 PM weekdays.

Art also has his own website at

September 23, 2007

Above a sketch from I. B. Lucas’ book illustrating the small plastic bags placed around each apple just after they have formed to prevent infestations of apple maggots. Each is held on with a staple and open at the bottom. Below, two shots of the same little corner of our garden here, the Erythronium blooms in the early spring, and then starting about a month ago the tiny cyclamen (Cyclamen hederifolium) appear. Author photos.

Murray Wallen, of Newmarket Ontario (just north of Toronto) wrote last Thursday with this not too uncommon question: “I have an apple tree that produces an abundant amount of fruit that is inedible. The fruit has brown strips all thru the apple and also has small dimples on the outside. I also have two Juniper bushes with red fruit in the fall directly below and beside this tree. Would the junipers be the cause of the rust like strips? I believe the junipers are an ornamental type. An answer would be most appreciated.”

Murray, I think you have a classic case of apple maggots (Rhagoletis pomenella). This is a pest for which there are not a whole lot of answers. It is generally described thus: egg-laying wounds are seen as small dimples or pin-pricks on the skin of the apple. This can cause deformation of the developing fruit or cause rapid decay of the area on softer varieties. The developing maggots tunnel throughout the fruit feeding on the ripening tissue. As the infestation progresses, brown squiggly lines appear on the fruit as the apple undergoes rapid ripening and decay. Infested fruit is unmarketable and unappetizing for most people. Early maturing and thin-skinned varieties of apples are more susceptible due to their timing and tendency of softer flesh.

Since the maggots only leave the damaged fruit as the apples fall to the ground, that is about the best control--to re-move every single fallen apple as soon as it falls.

However, there is a kind of odd-ball solution that I have ‘promoted’ for many decades. It was developed by a late friend, I. B. Lucas of Markdale Ontario in the early 60s and still works. Rather than repeating the entire instructions here, I will give you the URL to the page on my Website: .

Many to whom I’ve described this method have expressed their doubts as I mention in the old (2001) article, but it does work. I even have some lengths of poly that was used to protect tubular components of some metal furniture I bought here. I kept them because I though if I ever got an infestation of apple maggots, I would cut them up in the correct lengths and use them.

Murray also mentions the two ornamental junipers adjacent to his apple tree, questioning whether there might be a tie-in between the two. It may be Murray has read or heard of another pest known as Cedar-Apple rust. But the two are not connected at all. Cedar-Apple rust causes odd jelly-like formations on certain junipers; galls form and from these galls, during wet weather, orange-coloured gelatinous spore horns (called the telial stage) can been seen. It's the spores from these gelatinous formations that spread from the evergreens to infect any nearby apple or hawthorn trees. The affect on the evergreens is nil, but the disease is a major nuisance on the apple and hawthorn trees--particularly to commercial growers, and to gardeners if the trees are grown specifically for fruit production (rather than just as an ornamental tree).

The apple foliage first shows signs of the rust as tiny, pale-yellow spots on the upper surface about ten days after the evergreen's spore horns are fully developed. The spots are usually circular and enlarge, becoming orange-coloured. The tissue beneath the spots eventually swells and tiny, tubular projections appear, which later split and recurve. It is here that the spores that re-infect the evergreen foliage are produced. Damage to the apple trees occurs from loss of leaves, and mal-formation of some or the majority of the fruit. Control of this organism is most easily accomplished by removing one of the trees--either the apple, or the juniper. If this is not possible, spray the orange-coloured growths on the evergreens with household bleach at full strength, or from a hose-end sprayer set at its largest opening.

Portail in Toronto wrote to Donna Dawson last Saturday, and unsuccessfully tried to join our chat last Sunday. Tom Dawson and I are not sure just what happened, but she has promised to try again this Sunday. Her question was: “What blackberry varieties would thrive in Toronto? Are thornless as prolific as thorny? Do I need more than one plant? Can I plant it in a pot in the ground, to prevent spreading? Would it grow against a west fence? The plant would get partial sun from the east and south. Full sun for 4 hours. Thanks again.”

First Portail, let me tell you though I enjoy them, I have never grown blackberries! However, I think I can answer most of your questions. The difference between thorny and thornless cultivars is not nearly as important as is whether you grow an upright/erect cultivar, or a trailing cultivar. There are more thornless cultivars in the trailing type than in the erect type if that is one of your criteria.

Generally the upright cultivars are hardier than the trailing ones, although with some creative protection (such as Arbotex) applied just before the snow flies, the trailing ones are likely easier to bring through a tough winter.

It seemed to me that you were considering just one plant, and hoping to grow it in a (large) container which would be sunken into the ground in order to prevent the plant from spreading excessively. All of that should be possible, but you may be exaggerating the bush’s aggressiveness! I would plant a couple directly into the ground in the area you suggest provided there is in fact four hours at least of full sun daily And, you only need to have one cultivar, al-though if I were you I would try at least a couple. I suggest that Humber Nurseries is one place next spring where you should be able to get what you need.

You should remove the fruiting canes the first year, so the bush can gain strength. In the second and subsequent years, right after fruiting is complete, remove and burn or otherwise get rid of all those old canes. The canes that bore no fruit are the new ones that you leave, and will bear the following year.

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