Article Bank

FOLLOWING PUBLICATION OF EACH ISSUE of the Ontario Arborist magazine, we load copies of our most popular columns and features here in our article bank. In addition to being an invaluable source of information, the online versions contain an added benefit not possible in the magazine – live links. So remember, if you read an article in print and want to visit a link but don't want to type in a long address, simply find the article here and click away. One caveat: articles date back almost 10 years so some of the links referenced in earlier publications may no longer be valid. We do our best to keep them current or remove outdated links but the web changes daily!

Author: Jen Llewellyn
Issue: November-December 2007
Spending some time on the road in early to mid-October, you probably noticed the lovely display of fall colours that we had. I wasn’t expecting much of a show after such a long, hot, dry growing season but Mother Nature surprised us all in the end. The cool nights and sunny days were just perfect for expression and synthesis of the pigments that are responsible for those golden yellows, bright oranges and gorgeous reds that make us proud to be Canadian. By now there are just a few dull-coloured leaves left on the trees and the golden hues of our larches are beginning to fall away. November is a difficult month psychologically. I find the short days and dreary weather makes me want to crawl into bed right after dinner. I get “hibernation envy” in November. Wouldn’t it be nice to take the whole month off to just sleep and eat? That reminds me, I need to check my lottery ticket...
Author: Jen Llewellyn
Issue: January-February 2008
It seems as though we are seeing more than our fair share of trunk and branch cankers on deciduous trees in the last little while. One in particular that I’ve been hearing or reading about a lot is Hypoxylon canker (e.g. Hypoxylon mammatum, H. atropunctatum) on deciduous trees. At the early stages of infection, the tissue under the bark is invaded and eventually killed, causing a brown canker on the trunk or major branches after a couple of years. If you cut into the cambium with a sharp knife, you would see a dark mottling of the cambium and outer sapwood surrounding the visible young canker. The canker results in the localized death of the cambium, the conductive tissue that sends water and nutrients to the rest of the tree...
Author: Jen Llewellyn
Issue: March-April 2008
Just before Christmas, the Ontario Ministry of Natural Resources applied for an emergency use registration for a product that may help protect un-infested ash trees against emerald ash borer (Agrilus planipennis). The proposed product is TreeAzin, an injectable version of neem (azadirachtin) using their patented Ecoject™ system. Neem is a plant-derived insecticide that comes from a tropical tree species (Azadirachta indica) found in Africa, Asia and India...
Author: Jen Llewellyn
Issue: May-June 2008
Welcome to another whirlwind spring in southern Ontario. The leaves are out, the migratory birds are back and the insects are munching. Probably one of the most significant insect pests you saw in May was the viburnum leaf beetle. Yes I know, viburnums aren’t trees, but they are a very popular shrub that has been absolutely decimated by this beetle. Viburnum leaf beetle larvae hatch as the new foliage is emerging in the spring. They feed on the undersides of leaves and skeletonize them (leaving only the veins behind).
Author: Jen Llewellyn
Issue: July-August 2008
By the time you read this, we will have made it through another significant season of Gypsy Moth defoliation. I don’t know about you, but I was finding the caterpillars everywhere this spring. The worst damage always comes during the last couple of weeks of larval feeding. One thing we did see was some good parasitism of the larvae. Quite often we would find the larvae with a little white egg on their back, or clutching a white pupal case against the bottom side of their abdomen. These little hitchhikers are the larval stages of parasites, little parasitic wasps. And are they ever cool to see! If we get enough wet weather during late larval development, often times we will see a crash in the population due to a pathogenic fungus that kills the larvae, leaving the dead bodies hanging loosely from tree trunks; also nice to see. At this time, keep those tree bands sticky and up around the trees. If possible, try to place tree bands above visible pupal cases (otherwise emerged, flightless females will still be able to navigate up high in the tree to lay their egg masses). When removing tree bands, be prepared to scrape off egg masses behind and below the band. The vast majority of trees will recover from defoliation – the best thing you can do is provide those trees with a long, slow irrigation during hot, dry periods.
Author: Jen Llewellyn
Issue: November-December 2008
The annual Forest Helath Review took place in Orillia this year and members of the forestry, arboriculture and nursery industry gathered to hear about this year’s surveillance activities and research. Traditionally, forest health monitoring has been conducted by forest health specialists from the Ontario Ministry of Natural Resources (OMNR) and the Canadian Forest Service (CFS). Tony Hopkins, CFS, announced that in the future, OMNR will be taking complete control of forest health monitoring. In return, CFS plans to enhance their efforts in diagnostics, systematics and research to support forest health issues...
Author: Jen Llewellyn
Issue: January-February 2009
Each year, I consult with the nursery-landscape industry about their pest management problems and “needlecast diseases of conifers” always comes up as a major pest priority for growers and landscape professionals across Canada. We take these priorities to the annual Minor Use Workshops in Ottawa where we ask the Pest Management Centre (PMC) to conduct trials to help find effective, lower risk pesticide solutions and generate data for the registration of new products.
Author: Jen Llewellyn
Issue: May-June 2009
You know how lines from favourite movies pop into your head sometimes? Well I have a 5 year old, so I watch a lot of animated films. My favorite is Finding Nemo and we watched it again last week. It’s amazing how many things remind me of this movie...
Author: Jen Llewellyn
Issue: July-August 2009
When you consider all of the trees that are grown for the urban landscape, you will quickly come to realize that the number of possibilities is dwindling. Our streets used to be lined with majestic, vase-shaped elms – until Dutch elm disease came along. The ash tree was a popular and drought resistant species – until emerald ash borer surfaced. We used to be able to plant some native maples – until residential properties became so small and were graded with such poor soils that many native species will not survive, or will never reach their full potential and often become a hazard. The Norway maple (Acer platanoides) has been a successfully introduced street tree, lining residential streets and providing shade and habitat in several cities in Canada. Of course the problem is that the original species produces large amounts of seed and those seedlings are very shade tolerant and therefore highly competitive in our forested areas...
Author: Jen Llewellyn
Issue: September-October 2009
Looking around the landscape, you’ve probably noticed all the stunted leaves at the tips of branches on our street trees. Take a closer look at sugar, red, red-silver hybrids and Norway maples and you may see stunted, bushy leaves that look like they never fully emerged. In the summer, you may also have noticed that these leaves were quite chlorotic and the margins were often black. What gives? Most people attribute this to hot, dry weather in summer… but not this year. Would you believe that tiny leafhoppers are to blame?
Author: Jen Llewellyn
Issue: November-December 2009
The long, dark days of winter are upon us and I’m really feeling it this year. I never used to understand what people meant by seasonal affective disorder until more recently. I have friends who have those special lamps that they sit under; others who escape to a sunny place for a few days. Personally, I try to get through it with vitamin D, flannel pajamas and a good book. Okay, okay and a glass of wine/beer...
Author: Jen Llewellyn
Issue: January-February 2010
In the last couple of years, we’ve noticed a disease lurking on some of our deciduous trees. A fungal disease that has been misdiagnosed as winter injury. Botryosphaeria (“bot-ree-o-sferia”) are opportunistic fungi that cause cankers and dieback on branches, leaf blights and fruit rots of many woody plants. There are several species of Botryosphaeria, and some with some fairly wide host ranges...
Author: Jen Llewellyn
Issue: May-June 2010
People often come in my office and say, “How can you stand having so much stuff in here?” After 11 years, I decided it was maybe time to do something about it. So I cleaned out my office in early April. I was just finishing up when people starting coming in and saying, “How can you stand sitting on that chair?” Well, granted the chair upholstery is falling apart, so I conceded and promised to check with office surplus to see if there was something available...
Author: Jen Llewellyn
Issue: July-August 2010
This has been a brutal year for cedar leafminer injury on eastern white cedar (Thuja occidentalis) and its selections. I have received more phone calls about this pest in the landscape than any other this spring. Cedar leafminer (CLM) is actually a moth and there are quite a few species that have been identified on cedar in Ontario. The Ontario Ministry of Natural Resources has identified species of cedar leafminer in the genera Argyresthia and Pulicalvaria (Coleotechnites)...
Author: Jen Llewellyn
Issue: September-October 2010
Fall webworm is probably one of the most noticeable pests we encounter in the landscape. Everyone has noticed the thick, webbed larval tents on the ends of branches. Although their host list is a mile long, we see fall webworm most commonly on birch, black walnut, ash, cherry and apple. Larvae construct these webbed nests so they can hide in the relative safety of the thick web during the day. If you’ve ever tried to open up a webbed nest, you’ll experience just how tough they are...
Author: Jen Llewellyn
Issue: November-December 2010
Now I haven’t crunched the numbers, but I’d be willing to bet that nearly a third of the calls I get about troubled trees in the landscape pertain to Colorado spruce (Picea pungens). Most horticultural references describe Colorado spruce to be hardy, fairly drought tolerant (once established) and adaptable to a wide variety of soils but preferring rich, moist soil. I have seen this species growing in the nursery on a wide variety of soils types and soil pHs. It seems to do quite well on clay loams, especially where the fields are tile drained. It can also thrive on sandy loams that have organic matter in them. In the nursery, these trees are grown from young transplants with a full root system and they are managed to support optimum plant growth...
Author: Jen Llewellyn
Issue: January-February 2011
The debate between the use of native and non-native plants in the landscape has been a pretty hot topic in Canada and the United States. No doubt you’ve been having your own discussions with clients and colleagues...
Author: Jen Llewellyn
Issue: March-April 2011
Specifications for tree species can be puzzling these days what with the near-moratorium on planting ash (Fraxinus sp.) and Norway maple (Acer platanoides) in several jurisdictions. Callery pear (Pyrus calleryana) and honeylocust (Gleditsia tricanthos var. inermis) are still good choices but most plans are calling for more species biodiversity. So what else should we be planting, especially in tough urban sites?

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