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Articles : The Milkweeds of Canada (Asclepias spp.)

Status, Distribution, and Potential Impact from Noxious Weed Legislation

3.0 NOXIOUS WEED LEGISLATION
Because some species of Milkweed act in an aggressive or invasive manner in agricultural land and along roadsides, some provinces have included one or more species of Milkweed on their list of "noxious" plants that should or must be controlled or eradicated whenever they are found. There is no federal legislation that is concerned specifically with noxious weeds, however, the federal Department of Agriculture administers the Seeds Act that is indirectly concerned with weeds because the seed grade of crops is partly determined by the content of weed seeds (White et al., 1993).

Provincial Weed Acts address both weeds and weed seeds (White et al., 1993) and they will be summarized below in terms of their possible application to species of Milkweed. Provincial Weed Acts are normally laid out in two parts. The first part addresses the implementation of the Act in terms of obligations, procedures, penalties for non-compliance, and exceptions to the Act. The second part generally lists the species to which the Act applies and may indicate methods for destroying particular species (White et al., 1993). Newfoundland does not have weed control legislation nor are there any Milkweeds known from that province.

3.1 Weed Legislation Summary

Federal Seeds Act

The following information on federal weed legislation was provided by Tom Hodgson of Agriculture Canada, Ottawa. The Weed Seeds Order is part of the federal Seeds Act that identifies a number of plants as noxious weeds. There are no Milkweeds on the Weed Seeds Order list and Milkweed seeds are not seen as a problem in crop seeds.

Alberta

The following information on Alberta weed legislation was provided by Walter Yarish of Alberta Agriculture, Edmonton. There are no Milkweeds listed on the Alberta Weed Act but individuals may try to eliminate Milkweeds where there is a local problem. In Alberta, Milkweeds are not considered to be a significant problem and there is presently no program to try to eliminate any species of Milkweed in the province.

British Colombia

The following information on British Columbia weed legislation was provided by Dave Ralph of the Ministry of Agriculture, Kamloops. There are no species of Milkweed on the British Columbia Weed Act and no programs in place targeting Milkweeds.

Manitoba

The following information on Manitoba weed legislation was provided by Jo Anne Buth of Manitoba Agriculture, Carman. The Manitoba Weed Act has been recently revised and now lists only Common Milkweed (Asclepias syriaca) and Showy Milkweed (Asclepias speciosa). Showy Milkweed is only on the list because of some minor, local problems in a few municipalities, generally it is not considered to be a significant problem. Common Milkweed is not seen as a major problem, however, some municipalities are attempting to control the species and have active eradication programs on a "complaint" basis. Its abundance in the province varies from year to year and from area to area but it is generally considered to be static or increasing somewhat.

New Brunswick

The following information on New Brunswick weed legislation was provided by Kevin McCully of the New Brunswick Department of Agriculture. Although the New Brunswick Weed Act was written in 1969, it has never been proclaimed into law and there are no plans to do so in the near future.

Newfoundland

There is no weed control legislation in Newfoundland.

Nova Scotia

The following information on Nova Scotia weed legislation was provided by Doug Doohan of the Nova Scotia Department of Agriculture, Truro. Common Milkweed (Asclepias syriaca) is the only Milkweed listed in the Weed Act of Nova Scotia. There is an active program to eradicate the species from the province because although it is presently known from only a limited number of infestations-mostly in the Annapolis Valley-and thus vulnerable to concerted action, it is likely to increase in the future if there is no control program because of a recent shift in agricultural practices to low-tillage management. Such a shift by Ontario farmers has contributed to the recent increase of the species in agricultural land in that province.

Ontario

The following information on Ontario weed legislation was provided by Howard Lang, Ontario Ministry of Agriculture, Food, and Rural Affairs, Guelph. All species of Milkweed are listed as noxious weeds in the province but it is Common Milkweed that is the main concern and the only species against which measures are normally taken. There is no active program to target Milkweeds, rather, the main thrust is to respond on a "complaint" basis to control a particular problem-there is no attempt at eradication. For a complaint to be acted on, a species must be causing a problem for a horticultural or agricultural operation-no action is taken under the weed act against Milkweeds growing along roadsides or a vacant land unless there is a clear threat to adjacent property involved with agriculture or horticulture. Municipalities can act against noxious weeds but they are also primarily concerned with problems affecting agricultural or horticultural operations. Common Milkweed has been around for a long time and it does not seem to be an increasing agricultural problem.

Prince Edward Island

The following information on Prince Edward Island weed legislation was provided by Sherry Ross of the Prince Edward Island Department of Agriculture, Fisheries, and Forestry, Charlottetown. There are no species of Milkweed on the Prince Edward Island Weed Act.

Quebec

The following information on Quebec weed legislation was provided by Pierre Lavigne, Ministere de l'Agriculture, des Pecheries et de l'Alimentation, Sainte-Foy. Common Milkweed (Asclepias syriaca) is the only Milkweed listed in the Weed Act of Quebec. This species is a persistent problem in corn and soya bean fields but the population seems to be stable. There is no active program to control or eliminate Common Milkweed in Quebec.

Saskatchewan

The following information on Saskatchewan weed legislation was provided by Doug Billet of the Saskatchewan Department of Agriculture. Common Milkweed (Asclepias syriaca) is the only Milkweed listed in the Weed Act of Saskatchewan. This species is very sporadic in southeast Saskatchewan and the population seems to be stable. There is no active program to control or eliminate Common Milkweed because it is not seen as a problem.

TABLE 2: Summary of Weed Legislation Affecting Milkweeds

Milkweed Species Jurisdiction
CAN BC AB SK MB ON QC NB NS PE
Asclepias exaltata . . . . . X . . . .
A. hirtella . . . . . X . . . .
A. incarnata . . . . . X . . . .
A. lanuginosa . . . . . . . . . .
A. ovalifolia . . . . . X . . . .
A. purpurascens . . . . . X . . . .
A. quadrifolia . . . . . X . . . .
A. speciosa . . . . X . . . . .
A. sullivantii . . . . . X . . . .
A. syriaca . . . X X X X . X .
A. tuberosa . . . . . X . . . .
A. variegata . . . . . X . . . .
A. verticillata . . . . . X . . . .
A. viridiflora . . . . . X . . . .

AB=Alberta, BC=British Columia, CAN=Canada, MB=Manitoaba, NB=New Brunswick, NS=Nova Scotia, ON=Ontario, PE=Prince Edward Island, QC=Quebec, SK=Saskatchewan. An "X" in a cell indicates that the species is considered to be a noxious weed in that jurisdiction. If a cell is empty, it indicates that the species is not included in that jurisdiction's noxious weed legislation. Newfoundland does not have a weed control act.

3.2 Potential Impact from Weed Acts

There are 14 species of Milkweed that occur in Canada. Of these, only two species-Common Milkweed (Asclepias syriaca) and Showy Milkweed (Asclepias speciosa)-are considered to be problem weeds. Showy Milkweed (Asclepias speciosa) is listed as a noxious weed in Manitoba, however, it is not considered to be much of a problem in that province and is targeted only on a "complaint" basis.

Common Milkweed (Asclepias syriaca) is also listed as a noxious weed in Manitoba and although it is more common than Showy Milkweed, it is not considered to be a significant problem and it too is targeted only on a "complaint" basis. In Saskatchewan and Quebec, Common Milkweed is listed as a noxious weed but there is no active program in either province to target the species. In Saskatchewan the species is too rare to be a concern and in Quebec it is only regarded as a problem in two particular crops. Nova Scotia has a very localized population of Common Milkweed that the province considers to be a noxious weed and a threat to spread. For that reason, there is an active program in Nova Scotia to attempt eradication while the species is still confined and hence vulnerable.

The province of Ontario classifies all Milkweeds as noxious weeds, however, the primary concern is for Common Milkweed. Although there have been attempts to control Common Milkweed in particular areas, there is no broad-scale program to eradicate the species. Considering the abundant and spreading population of Common Milkweed in the province, it is unlikely that there are sufficient resources available to significantly reduce the species in Ontario even if a broad program was undertaken.

The Monarch Butterfly (Danaus plexippus) occurs across much of Canada as adults, however, its breeding range is mainly restricted to south and central Ontario, and southern Quebec. Although the Monarch larva can feed on a range of Milkweed species, it is largely dependent on Common Milkweed (Asclepias syriaca). From the point of view of the Monarch Butterfly, it is primarily the Ontario populations of Common Milkweed that are most important to its breeding in Canada. The enforcing of noxious weed legislation in some provinces-like Nova Scotia-could impact peripheral colonies of Monarch Butterflies. In Ontario, however, where there is a very abundant and spreading population of Common Milkweed, it seems unlikely that enforcing the noxious weed act could put the Monarch Butterfly at significant risk.

3.0 NOXIOUS WEED LEGISLATION
Because some species of Milkweed act in an aggressive or invasive manner in agricultural land and along roadsides, some provinces have included one or more species of Milkweed on their list of "noxious" plants that should or must be controlled or eradicated whenever they are found. There is no federal legislation that is concerned specifically with noxious weeds, however, the federal Department of Agriculture administers the Seeds Act that is indirectly concerned with weeds because the seed grade of crops is partly determined by the content of weed seeds (White et al., 1993).

Provincial Weed Acts address both weeds and weed seeds (White et al., 1993) and they will be summarized below in terms of their possible application to species of Milkweed. Provincial Weed Acts are normally laid out in two parts. The first part addresses the implementation of the Act in terms of obligations, procedures, penalties for non-compliance, and exceptions to the Act. The second part generally lists the species to which the Act applies and may indicate methods for destroying particular species (White et al., 1993). Newfoundland does not have weed control legislation nor are there any Milkweeds known from that province.

3.1 Weed Legislation Summary

Federal Seeds Act

The following information on federal weed legislation was provided by Tom Hodgson of Agriculture Canada, Ottawa. The Weed Seeds Order is part of the federal Seeds Act that identifies a number of plants as noxious weeds. There are no Milkweeds on the Weed Seeds Order list and Milkweed seeds are not seen as a problem in crop seeds.

Alberta

The following information on Alberta weed legislation was provided by Walter Yarish of Alberta Agriculture, Edmonton. There are no Milkweeds listed on the Alberta Weed Act but individuals may try to eliminate Milkweeds where there is a local problem. In Alberta, Milkweeds are not considered to be a significant problem and there is presently no program to try to eliminate any species of Milkweed in the province.

British Colombia

The following information on British Columbia weed legislation was provided by Dave Ralph of the Ministry of Agriculture, Kamloops. There are no species of Milkweed on the British Columbia Weed Act and no programs in place targeting Milkweeds.

Manitoba

The following information on Manitoba weed legislation was provided by Jo Anne Buth of Manitoba Agriculture, Carman. The Manitoba Weed Act has been recently revised and now lists only Common Milkweed (Asclepias syriaca) and Showy Milkweed (Asclepias speciosa). Showy Milkweed is only on the list because of some minor, local problems in a few municipalities, generally it is not considered to be a significant problem. Common Milkweed is not seen as a major problem, however, some municipalities are attempting to control the species and have active eradication programs on a "complaint" basis. Its abundance in the province varies from year to year and from area to area but it is generally considered to be static or increasing somewhat.

New Brunswick

The following information on New Brunswick weed legislation was provided by Kevin McCully of the New Brunswick Department of Agriculture. Although the New Brunswick Weed Act was written in 1969, it has never been proclaimed into law and there are no plans to do so in the near future.

Newfoundland

There is no weed control legislation in Newfoundland.

Nova Scotia

The following information on Nova Scotia weed legislation was provided by Doug Doohan of the Nova Scotia Department of Agriculture, Truro. Common Milkweed (Asclepias syriaca) is the only Milkweed listed in the Weed Act of Nova Scotia. There is an active program to eradicate the species from the province because although it is presently known from only a limited number of infestations-mostly in the Annapolis Valley-and thus vulnerable to concerted action, it is likely to increase in the future if there is no control program because of a recent shift in agricultural practices to low-tillage management. Such a shift by Ontario farmers has contributed to the recent increase of the species in agricultural land in that province.

Ontario

The following information on Ontario weed legislation was provided by Howard Lang, Ontario Ministry of Agriculture, Food, and Rural Affairs, Guelph. All species of Milkweed are listed as noxious weeds in the province but it is Common Milkweed that is the main concern and the only species against which measures are normally taken. There is no active program to target Milkweeds, rather, the main thrust is to respond on a "complaint" basis to control a particular problem-there is no attempt at eradication. For a complaint to be acted on, a species must be causing a problem for a horticultural or agricultural operation-no action is taken under the weed act against Milkweeds growing along roadsides or a vacant land unless there is a clear threat to adjacent property involved with agriculture or horticulture. Municipalities can act against noxious weeds but they are also primarily concerned with problems affecting agricultural or horticultural operations. Common Milkweed has been around for a long time and it does not seem to be an increasing agricultural problem.

Prince Edward Island

The following information on Prince Edward Island weed legislation was provided by Sherry Ross of the Prince Edward Island Department of Agriculture, Fisheries, and Forestry, Charlottetown. There are no species of Milkweed on the Prince Edward Island Weed Act.

Quebec

The following information on Quebec weed legislation was provided by Pierre Lavigne, Ministere de l'Agriculture, des Pecheries et de l'Alimentation, Sainte-Foy. Common Milkweed (Asclepias syriaca) is the only Milkweed listed in the Weed Act of Quebec. This species is a persistent problem in corn and soya bean fields but the population seems to be stable. There is no active program to control or eliminate Common Milkweed in Quebec.

Saskatchewan

The following information on Saskatchewan weed legislation was provided by Doug Billet of the Saskatchewan Department of Agriculture. Common Milkweed (Asclepias syriaca) is the only Milkweed listed in the Weed Act of Saskatchewan. This species is very sporadic in southeast Saskatchewan and the population seems to be stable. There is no active program to control or eliminate Common Milkweed because it is not seen as a problem.

TABLE 2: Summary of Weed Legislation Affecting Milkweeds

Milkweed Species Jurisdiction
CAN BC AB SK MB ON QC NB NS PE
Asclepias exaltata . . . . . X . . . .
A. hirtella . . . . . X . . . .
A. incarnata . . . . . X . . . .
A. lanuginosa . . . . . . . . . .
A. ovalifolia . . . . . X . . . .
A. purpurascens . . . . . X . . . .
A. quadrifolia . . . . . X . . . .
A. speciosa . . . . X . . . . .
A. sullivantii . . . . . X . . . .
A. syriaca . . . X X X X . X .
A. tuberosa . . . . . X . . . .
A. variegata . . . . . X . . . .
A. verticillata . . . . . X . . . .
A. viridiflora . . . . . X . . . .

AB=Alberta, BC=British Columia, CAN=Canada, MB=Manitoaba, NB=New Brunswick, NS=Nova Scotia, ON=Ontario, PE=Prince Edward Island, QC=Quebec, SK=Saskatchewan. An "X" in a cell indicates that the species is considered to be a noxious weed in that jurisdiction. If a cell is empty, it indicates that the species is not included in that jurisdiction's noxious weed legislation. Newfoundland does not have a weed control act.

3.2 Potential Impact from Weed Acts

There are 14 species of Milkweed that occur in Canada. Of these, only two species-Common Milkweed (Asclepias syriaca) and Showy Milkweed (Asclepias speciosa)-are considered to be problem weeds. Showy Milkweed (Asclepias speciosa) is listed as a noxious weed in Manitoba, however, it is not considered to be much of a problem in that province and is targeted only on a "complaint" basis.

Common Milkweed (Asclepias syriaca) is also listed as a noxious weed in Manitoba and although it is more common than Showy Milkweed, it is not considered to be a significant problem and it too is targeted only on a "complaint" basis. In Saskatchewan and Quebec, Common Milkweed is listed as a noxious weed but there is no active program in either province to target the species. In Saskatchewan the species is too rare to be a concern and in Quebec it is only regarded as a problem in two particular crops. Nova Scotia has a very localized population of Common Milkweed that the province considers to be a noxious weed and a threat to spread. For that reason, there is an active program in Nova Scotia to attempt eradication while the species is still confined and hence vulnerable.

The province of Ontario classifies all Milkweeds as noxious weeds, however, the primary concern is for Common Milkweed. Although there have been attempts to control Common Milkweed in particular areas, there is no broad-scale program to eradicate the species. Considering the abundant and spreading population of Common Milkweed in the province, it is unlikely that there are sufficient resources available to significantly reduce the species in Ontario even if a broad program was undertaken.

The Monarch Butterfly (Danaus plexippus) occurs across much of Canada as adults, however, its breeding range is mainly restricted to south and central Ontario, and southern Quebec. Although the Monarch larva can feed on a range of Milkweed species, it is largely dependent on Common Milkweed (Asclepias syriaca). From the point of view of the Monarch Butterfly, it is primarily the Ontario populations of Common Milkweed that are most important to its breeding in Canada. The enforcing of noxious weed legislation in some provinces-like Nova Scotia-could impact peripheral colonies of Monarch Butterflies. In Ontario, however, where there is a very abundant and spreading population of Common Milkweed, it seems unlikely that enforcing the noxious weed act could put the Monarch Butterfly at significant risk.

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