The Canada thistle stem-mining weevil (Hadroplontus litura) occurs naturally in France, Switzerland, Austria, Germany, Britain, and southern Scandinavia. It was first introduced into Canada as a biological pest control agent in 1965. These agents have proven to be an effective method for control of Canada thistle.
Eggs are laid in the mid-vein of the rosette leaves in early spring and hatch after five to nine days. Larvae internally mine the inside of the stem of the thistle plant as the shoot elongates during the summer. Fully developed larvae will exit the plant at the root and enter the soil to pupate. They will emerge again in their adult form later in the summer and feed on thistle leaves before winter. Adults will overwinter in the soil, ready to attack the emerging thistle the following spring.
After a careful review of our biological control agent for Canada thistle program, WCFA has made the decision to discontinue this program for the time being. This means WCFA will no longer be importing and delivering Canada thistle stem-mining weevils, or stem-gall flies for the foreseeable future.
We appreciate the many of you who have supported this program in the past, and we apologize for any inconvenience this decision may cause. Please see below for resources related to the insects should you wish to pursue obtaining some yourself.
Stem-Mining Weevil Suppliers
Import Information
