Pests & Diseases of Trees & Shrubs

Dormant Spray

With our early spring and the buds of plants getting ready to open, now is the time to think about doing a Dormant Spray. Combine Horticulture Oil and Lime Sulphur to kill overwintering insects (such as scale and mites), insect eggs, and diseases on certain hardy landscape plants.

This combination spray can only be applied in early spring before leaf buds show green.  Applying at the incorrect time can burn leaf buds that have started to swell or show any sign of green.

This is best applied to fruit trees, roses, ornamental shrubs like Highbush Cranberry, cotoneaster and Cranberry, evergreens such as Cedars, trees like Hawthorn and Crab Apple & Apple. Do not use a dormant spray on Butternut or Colorado Blue Spruce.

Choose a warm day (above  5°C ) from March thru to April. Spray early in the morning so the plant will be completely dry by evening. Do not spray if there is any chance of frost overnight. It is also best to spray when there is no or minimal wind.

Mix Lime Sulphur and Horticulture Oil (available together as a Dormant Spray Kit) according to the package directions in a hose end sprayer that attaches to your garden hose or in a 1 or 2 gallon tank sprayer.

In all cases, spray the plant starting at the top until it just starts to drip off the branches. If you start spraying from the bottom, you will run out of product before the job’s done.

For roses, be sure to spray the soil around the base of the plant as well to control Powdery Mildew and Black Spot.

Mix only what you can use. You cannot save the prepared solution for later use.

Wear protective clothing, and anti-splash goggles. Wash hands and face after use.

Do not let any of the mixture fall or drift onto such hard surfaces as it may leave a permanent stain. Cover the area with plastic to avoid staining.

Check Your Evergreens for Signs of this Pest

You can eradicate it by squishing it, washing it off with your soapy water or using a spray like Sevin or BTK.

Black Knot Disease

Does your tree or your neighbors tree look like this.

Damage by Rabbits, Mice or Voles

Unfortunately rabbits and mice or voles have not enjoyed the prolonged snow and are looking for food. They have been busy on the nursery and in homeowner yards, eating the bark on the trees.  If your tree looks like this, and is eaten around the entire trunk, it may not survive.  The bark and transplant tissue (phloem) which carries the nutrients from the leaves to the roots have been damaged.    One method that may save your tree is by applying Lac Balsam to the area.  It works like a rubber skin and seals the cambium on the tree so the nutrients can flow again.  For $12.95 for a 150 gr. tube, it is well worth trying out.

Fall Needle Shed

Yellowing of needles in the fall is a normal occurrence for evergreen trees.  Conifers do not keep their growth of needles on their inside branches  and shed them naturally in the fall.  The discoloration, which affects the older needles close to the trunk occurs in late August and can continue until freeze up.   The amount of shedding can be greater if the tree has been placed under stress caused by droughts, flooding or newly dug trees.   These needles are not replaced and this is why evergreens are bare of needles near the trunk and there is usually a carpet of needles under the tree.