Biocontrol News

Current Biocontrol News

New Biocontrol Agent: Bradyrrhoa gilveolella

March 6, 2009

In 2007, The BC Ministry of Forests and Range imported a new biocontrol agent for the control of rush skeletonweed, (Chondrilla junceae). The agent, Bradyrrhoa gilveolella is a root-feeding moth approximately 11 - 13 mm long with creamy buff-coloured wings. There are three brown bands traversing their anterior wings and their wingspan is from 25 mm to 28 mm across.

The adult moths where received from Dr. Mark Schwarzlaender of the University of Idaho on July 19, 2007. Twelve and 15 moths were released into two enclosed propagation tents in the north Okanagan, respectively. During transport, some moths oviposited eggs into the shipping containers. These eggs were returned to Agriculture and Agri-Food Canada's labs in Lethbridge by Dr. Rose DeClerck-Floate where she had them transferred onto potted rush skeletonweed host plants and held in growth chambers. On September 19, 2007, 27 plants containing 140 larvae and 25 plants containing 106 larvae were returned to BC and transplanted into two additional propagation tents at the same north Okanagan location, respectively.

In 2008, the four tents were regularly inspected starting April 1 for the presence of moths. From the beginning of July to the third week in September, the checks rotated between early morning, throughout the day and in the evening to ensure any existing moths would be seen. On August 5^th and again on the 6^th and 7^th, a single moth was recorded in a single tent. On August 18^th, 19^th and 25^th two moths were recorded each time in a single tent, but, in a different tent than the earlier sightings. These observations took place in the morning, during the day and in the evening. It is possible that these moths may have bred, if they were separate genders, however, no eggs were observed at later dates. Both tents that yielded moths were those which had received infested, transplanted plants.

The USA also has not had much success with establishing B. gilveolella. Dr. Jeff Littlefield of Montana State University reports they have had the agent overwinter but only one larvae and a few empty pupal cases have been observed in the field (pers. comm. March 2009). Both countries are considering additional releases of the biocontrol agent while bearing in mind whether the originating European population was collected from habitat conducive to North America.