The arrival of Lysathia sp. at CABI Switzerland quarantine. Credit: CABI

Multiple choice host range test set-up with Lysathia sp. Credit: CABI

Collection of test plants for host range testing of agents against parrot feather. Credit: CABI

The invasion of parrot feather in drainage, ditches, canals and rivers in British Columbia. Credit: David Ensing, AAFC

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Project Overview

So, what’s the problem

Parrot’s feather is a noxious weed which has invaded the Lower Mainland and Vancouver Island, British Columbia and extended into the western USA, including Washington, Oregon, Idaho and California. In the invaded range, parrot’s feather has the ability to form dense impenetrable mats which affect stream flow, reduce native species’ richness, reduced water quality and habitat quality for fish and wildlife, and negatively impact human activities. In North America, it is considered a serious weed in shallow streams, irrigation ditches, ponds and shallow lakes. In urban settings, it significantly increases the risk of flooding when it invades canals, ditches and storm drains that would typically divert flood waters.

Once established, this plant is extremely difficult to control. Any mechanical method can fragment plants, favouring the growth and spread of this species. In addition, herbicides have been difficult to employ due to restrictions in use in sensitive wetland habitats and the fact that the plant has an emergent and submerged form.

Biological control of this species was implemented in South Africa in the early 1990s with the release of the leaf-feeding flea beetle, Lysathia sp. which proved to be extremely effective and no additional agents were required. Despite this success, no other country has implemented biological control against this weed.

What is this project doing?

In 2020, CABI Switzerland initiated a project to evaluate the potential for biological control of parrot’s feather in western North America.

There are three potential biological control agents that are worth further investigation: the leaf-feeding flea beetle, Lysathia sp. and the stem-mining weevil, Listronotus marginicollis are species native to South America and have been developed as part of the biological control programme for parrot’s feather in South Africa. The third, a North American native weevil Phytobius vestitus, was recently identified in Louisiana damaging parrot’s feather to the extent that it was managing parrot feather in certain locations. This project aims to evaluate these agents.

All three agents have the potential to be effective and safe biological control agents. However, before any agent can be considered for safe release in western North America, host-range testing of plant species, relevant to the region, will need to be conducted.

Climate is considered a potential limiting factor, however, preliminary Climex models provided a moderate fit to some sites where both Lysathia sp. and L. marginicollis occur. Nevertheless, it needs to be kept in mind that Vancouver has longer winters than those experienced in South Africa and Argentina. In addition to the host range testing, this project will explore the potential climatic compatibility of these agents to Canada which will give insights into the efficacy of the agents.