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Unchecked invasive, noxious weed could devastate Delta, BC shores

Treatments will be limited to direct applications to actively growing Spartina plants
delta, bc map
A map of Delta showing its extensive shoreline. Parts Boundary Bay, Roberts Bank and Westham Island will be treated with herbicide to control the invasive Spartina plant.

A plan is in the works to again spray herbicide on parts of the shores of Delta’s Boundary Bay to try and eradicate an invasive weed, which left unchecked, could be devastating to the local ecosystem.

The Ministry of Forests, Lands, Natural Resource Operations and Rural Development has applied to the Ministry of Environment and Climate Change Strategy for a pesticide use permit, under the BC Integrated Pest Management Act, to authorize the application of herbicide to get rid of intertidal cordgrasses known as Spartina anglica.

It is designated as a noxious weed under the Weed Control Act and the ministry has been actively controlling it in Boundary Bay and Robert's Bank since 2003.

Delta council earlier this year supported the ministry's pesticide use permit application.

Spartina anglica forms monotypic meadows that out-compete native species and decrease the area of productive intertidal mudflats that are important for shorebirds, juvenile fish, marine shellfish and other invertebrates.

The meadows also alter the elevation and drainage pattern of the intertidal areas, which may increase the risk of coastal flooding.

Pesticide use permits have been issued since 2013, having a maximum three-year duration. The current application is for 2022 to 2025.

A Delta staff report to council notes the control success rate has improved substantially since herbicides have been employed.

In 2016, 7.93 hectares required treatment, while only 0.79 hecatres required treatment in 2021.

The ministry expects a continuing downward trend in Spartina size and density with consistent chemical control, the memo noted.

There are no changes to the proposed treatment areas at Boundary Bay, Robert's Bank and Westham Island and the area will be sprayed by ground crews once a year.

The proposed treatment area of up to 10 hectares is not decreasing to provide flexibility for additional herbicide application should new infestations be discovered.

Delta also provides staff support through the Invasive Plant Management Team to help map the

extent of Spartina in Boundary Bay and Robert's Bank.

Delta is part of the B.C Spartina Working Group, formed in 2004.

It’s a partnership of different governments, non- government organizations and industry collaborating to eradicate invasive Spartina species from B.C.'s shores.

A study concluded in 2008 found that ocean currents could carry Spartina seeds and root fragments to the full extent of B.C.'s coastline, much of it possessing suitable habitat for Spartina.

The province says that left uncontrolled, Spartina will likely spread in distribution and density across tens of thousands of hectares, leading to loss of migratory bird habitat, as observed in estuaries in Washington and California.