Ornamental Pear trees have been recently under attack from a hard to treat fungus known as Trellis rust. Originally from Europe, Trellis rust or European Pear Rust is caused by the rust fungus Gymnosporangium sabinae. The disease may present a serious health threat to members of the Pyrus species, including both ornamental and fruit pear types. Ornamental Pear trees have been popular trees planted for decades noted for their fast growth rate, tolerance of urban conditions, fairly compact shape and white blooms that appear in early spring. Unfortunately, hundreds of trees have been noted dying in Rockville Center and the disease has been spreading to the Nassau and Suffolk County areas of Long Island. The fungus has spread from the mid-western states to upstate New York and Connecticut over the past several years and seems to be getting progressively worse. According to horticulturists, part of the problem is that the trees have been over-planted, resulting in a rapid spreading of the disease.
Symptoms to look out for are yellow-orange leaf spots (see photograph), which develop into spores in late summer. The spores can be spread to other host plants by wind or to the roots if the trees are close enough together. The secondary host during the winter months is juniper, allowing the fungus to survive when the pear trees drop their leaves; hence, continuing the cycle in the spring.
If you spot damage on your tree, remove and destroy the infected leaves to prevent spores from spreading. If caught early enough, systemic and spray fungicides can be applied to inhibit the spread of the disease. Best preventive measures are to be alert in monitoring your trees, and when in doubt, call a tree professional.
Very often larger landscape trees and shrubs will arrive either wrapped in burlap or burlap encased in wire baskets. These allow the tree to be picked up by the root ball instead of the trunk and are used to protect the roots during transportation and handling. Also, on many occasions large tree spades are used by growers to dig the tree for transportation. These giant spades will cause surrounding soil to be pushed up higher around the trunk way past the flare. When planting, burlap or wire baskets should be removed completely or pushed down as far as possible below the soil surface to allow for the tree to develop new feeder roots, and the root flare should be visible. Care should be taken both during the arrival and planting of the tree to ensure its survival. Here are some recommendations.
Some horticulturists recommend removing at least the top 12 to 18 inches (two or three levels) of wire from the root ball with larger trees, or the entire basket when possible. (Source: University of Florida Horticultural Department). Dig the hole the tree is being planted in wide enough so that the wire basket can be cut and folded down around the plant. Cut and remove any top burlap and do the same, pushing the burlap as far down as possible (if not removing it completely). It is alright to leave the bottom portion of the burlap or basket intact if the root ball does not appear stable enough to remove it. Wire baskets are known to degrade slowly in soil, and can be intact up to 20 years after planting; however, the welded joints tend to degrade sooner. Natural burlap typically tends to rot in the soil, with the exception of some of the drier parts of the country (regions receiving less than about 20 inches of annual precipitation). Synthetic burlap does not decompose. To distinguish between natural and synthetic burlap burn a small portion with a match. Synthetic burlap has a smoother feel and often smokes and melts. Natural burlap is coarser and usually burns with a flame and turns to ash, while synthetic does not.
When positioning the tree check for the root flare (see diagram above) and remove any soil that may have been pushed up when digging. The root flare is pointed out as the lower line on the diagram where the trunk gets wider. The tree will develop new feeder roots near the top of the root ball enabling the tree to receive water, undergo oxygen exchange and obtain minerals. It is not uncommon to see the tree’s root ball covered with additional soil. If not removed the tree will be buried too deeply and will often send roots growing straight upward where conditions are better. Over time this will cause the tree to stress and slowly suffocate due to a lack of water and oxygen or girdling root (roots wrap around the base of the tree and suffocate it).
Now that the burlap and wire are pushed away from the roots it is time to plant. Position the tree slightly above the grade (1-2 inches) to allow for proper drainage and mulching once the tree is planted. This will also ensure proper transportation of water, oxygen and minerals, as discussed above. As a general rule of thumb plant one inch above grade for each inch caliper of tree trunk. For example, a tree with a one inch trunk caliper (diameter) should be one inch above grade, and so forth.
In a heavily clay soil it is recommended to plant even a little higher to allow for proper drainage, If drainage does seem to be an issue, it may be in your best interest to dig pilot holes two to three feet down and add a gravel base so that water percolates downward, instead of having water sitting right at the roots. Trees in standing water will lose their feeder roots due to suffocation and will quickly decline. Following these simple planting techniques will ensure the longevity of your trees for many years. The same guidelines apply to the planting of deciduous trees or plants in plastic containers. Remember it is important to mulch your tree to protect the roots but prevent the mulch from being right up around the trunk to avoid any issues. I see way too much of this! (see article)
Now that we have covered the proper techniques it is time to go out into the garden and get some trees planted!
As Always…Happy Gardening!
2015 Lee@ A Guide to Landscape Design & Maintenance.