Dormant Oil And Lime Sulphur

Protection For Fruit Trees, Ornamentals And More

From Your Friends At Schriemer's

Are you looking for an organic way to manage pests and disease on your trees and shrubs? Dormant oil and lime sulphur are an effective control for overwintering insects and fungal diseases that trouble many common deciduous trees and shrubs in Manitoba. These two products are low toxicity, relatively organic and safe for the environment, and can help cut back on the use of pesticides during the growing season. They make a fine alternative to commercial pesticides, and have been used by orchard farmers for many hundreds of years.

Dormant oil, also known as horticultural oil, works by suffocating the overwintering eggs of pests like scale, mites, aphids and thrips. Lime sulphur controls fungal diseases such as black spot, rust and canker that overwinter on the bark or in nooks and crannies. Because of their similar application and timing, the two are usually applied in combination. This combination can be used on most deciduous trees and shrubs, fruits and ornamentals. Do not use them on evergreens, and avoid using them on maples, nut trees and members of the viburnum family.

The timing of application is important. Critically, the plant must be dormant, i.e. the leaf and flower buds have not yet broken. Spraying should be done on a warm sunny day when temperatures are well above freezing, with no chance of rainfall for at least 24 hours. This is usually around late March or early April in Manitoba.

Dormant oil and lime sulphur are best applied using a pressure sprayer to ensure even application and thorough coverage. Follow the instructions on the labels when mixing your spray. Be sure to wear appropriate work clothing and rubber gloves, as the mist can stain clothing. As well, lime sulphur will stain concrete, white stucco and siding, so use cautiously on plants against the house or use a polyethylene backdrop when spraying.

Using the sprayer, apply the combination as a fine mist until it forms drips and runs down the branches and bark. Start at the top of each plant and spray downwards. Don't worry about it running into the soil or grass - it is harmless to these. You should ideally spray the plants two or even three times for maximum effect, although once is often enough.

You can purchase dormant oil, lime sulphur and combination kits at Schriemer's, along with pressure sprayers. Our experts will also be happy to give you advice at the Integrated Pest Management counter.