In 2012 I wrote an article entitled "Herbicide Choices for Controlling Weed Hosts of Spotted Wing Drosophila". Since the publication of this article there have been a number of questions regarding when and where it is okay to spray these weedy hosts: buckthorn (considered an invasive species) cherry, chokecherry, elderberry, mulberry, raspberry, etcetera. All of the herbicides listed can be sprayed in woody areas or along fencerows if the species is on the label. If you are considering spraying near a riparian area, please review the herbicide label carefully to determine the buffer zone requirements for spraying wooded areas and vegetated areas adjacent to water (riparian area).

From Wikipedia: A riparian zone or riparian area is the interface between land and a river or stream. Plant habitats and communities along the river margins and banks are called riparian vegetation, characterized by hydrophilic plants. Riparian zones are significant in ecology, environmental management, and civil engineering because of their role in soil conservation, their habitat biodiversity, and the influence they have on fauna and aquatic ecosystems, including grassland, woodland, wetland or even non-vegetative. In some regions the terms riparian woodland, riparian forest, riparian buffer zone, or riparian strip are used to characterize a riparian zone. The word "riparian" is derived from Latin ripa, meaning river bank.

The most dramatic effects of herbicides on non-target plants and animals often result from the habitat alterations they cause by killing the targeted weeds. For example, loss of invasive riparian plants can cause changes in water temperature and clarity that can potentially impact the entire aquatic community, and the physical structure of the system through bank erosion. Removing a shrubby understory can make a habitat unsuitable for certain bird species and expose small mammals to predation.

Bottom line, read the herbicide label carefully and follow the buffer zone restrictions. If weed hosts of SWD are present within the buffer zone area you cannot spray.

Spraying invasive species that do not have herbicides registered for control

If you are considering spraying an invasive species such as buckthorn, the Ontario Pesticides Act and Ontario Regulation 63/09 provide natural resources, forestry and agricultural exceptions which may enable chemical control of invasive plants on your property.

Natural Resources Exception

A 'natural resources' exception exists for the use of prohibited pesticides to manage, protect, establish or restore a natural resource. This exception allows the use of prohibited herbicides for control of invasive plants on your property provided your project meets specific conditions and you obtain the necessary approvals.

If your project meets the natural resources criteria specified in section 33 of Ontario Regulation 63/09 and includes the use of pesticides in accordance with Integrated Pest Management principles outlined in the BMP guide you will need to contact the Ontario Ministry of Natural Resources ( to obtain a written letter of opinion from the MNR Regional or Branch Director.

Forestry Exception

If buckthorn is within a forest*, chemical control may fall under the exception for forest management, and a letter of opinion may not be required. Class 9 pesticides can be used under the forestry* exception to protect trees from pests and to control competing vegetation.

*O. Reg. 63/09 defines "forestry" and "forest" as:

Forestry means activities relating to any of the following: harvesting, renewing, maintaining or establishing a forest, protecting forest resources derived from a forest, and accessing a forest for these purposes.

Forest means a treed area of land that is one hectare in size or larger and is not used for producing an agricultural crop as part of an agricultural operation.

Refer also to the Ministry of Environment's factsheet titled "Pesticides Act and Ontario Regulation 63/09 Private Land and Woodlot Owners April 2011".

Agriculture Exception

There is an exception for the use of Class 9 pesticides for uses related to agriculture by a farmer. This exception may apply to the control of buckthorn in agricultural fields or near farm operations.

A farmer is an individual who owns or operates an agricultural operation.

An agricultural operation is an agricultural, aquacultural or horticultural operation and includes:

  • Growing, producing or raising farm animals;
  • Production of crops, including greenhouse crops, maple syrup, mushrooms, nursery stock, tobacco, trees and turf grass, and any additional agricultural crops;
  • Activities that are part of an agricultural operation such as maintenance of a shelterbelt for the purposes of the agricultural operation; and,
  • The production of wood from a farm woodlot, if at least one of the activities described earlier is carried out on the property where the farm woodlot is located.

Refer also to the Ministry of the Environment's factsheet titled "Pesticides Act and Ontario Regulation 63/09 Agriculture May 2011".