Canada thistle is one of Colorado's most widespread and damaging exotic invasive weed, infesting croplands as well as pastures, rangelands, roadsides and other non-crop areas. The United States Department of Agriculture (USDA) and the Colorado Department of Agriculture (CDA) have entered into a cooperative agreement to control the noxious weed Canada thistle using a rust fungus.
The four-year agreement provides $392,000 to the CDA's Biological Pest Control Program to harvest and redistribute the rust fungus to uninfected patches of Canada thistle and monitor the decline of the weed following infection. If successful, the program is expected to help landowners and weed managers save millions of dollars by reducing weed infestations and cutting control costs.
The fungus, known as Puccinia punctiformis, only attacks Canada thistle and kills the plant by infecting the root system.
The Colorado Department of Agriculture's Insectary, located in Palisade, will begin the Canada thistle biological control project in the spring of 2014. The project will consist of the discovery of naturally occurring fungal infections on Canada thistle plants in Colorado, harvest of teliospores (the infective stage of the rust), and distribution of the spores to uninfected Canada thistle patches.
"Timing is everything with the project. The initial survey of thistle patches for naturally occurring rust must happen in the spring when infected plants are visible, while teliospores only appear and can be harvested in the summer," said Dan Bean, CDA's Biological Pest Control Director. "Infection of rust-free Canada thistle patches using the teliospores is possible in the late summer and fall, when new and susceptible foliage begins to grow from the root system."
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