Biological Control Of Rangeland Weeds

March 20 is the first day of spring. Soon the weather will warm and plants will begin to grow. The prairies will fill with beautiful native grasses, flowers, shrubs and (unfortunately) rangeland weeds. There are several foreign plants that are considered rangeland weeds such as leafy spurge, salt cedar, Canada thistle, hounds tongue and field bindweed. These plants have few to no predators native to the area and thrive in the environment. This means they can spread, unchecked, during the growing season and often crowd out the native plant life; competing for sunlight, space, and nutrients essential for growth. Rangeland weeds can also be distasteful, poisonous or cause husbandry problems for livestock and wildlife costing ranchers and environment managers valuable time and thousands of dollars in corrective measures and production. Unfortunately, these plants can be tough and traditional methods of controlling them such as herbicide, mowing and grazing may not be effective enough or at all. Fortunately, there is another way.

Biological control is the use of insects or pathogens to control pest species of plants or animals. It can be more cost-effective than herbicides and cutting as well as more targeted than grazing. The USDA ARS in Sidney, MT has been looking into biological controls of rangeland weeds for years. They mostly focus on the use of insects. Insects, If successful, are self-perpetuating and can move to other areas in need of treatment without intervention. The trick is to find an insect that is host specific to the targeted weed. This is done by identifying the specific species of the weed. Then it must be studied in its native country to discover its natural predators and find any that feed only on that plant. Then the insects are brought to this area and kept in quarantine while they are tested for survivability, whether they will eat the plant when it is grown in this area and to be sure they will still only feed on the targeted weed. Plants, when in a non-native environment for a long time, can change. Host-specific insects may not feed on them. Once approved, ranchers and environmental managers may contact their local weed agent or the Montana Biological Control Project for that weed online to acquire biological controls for their land. They can be purchased but are usually free or available at a nominal cost.

Friday, March 9, at noon Natalie West, a research ecologist at the USDA ARS, spoke about this in her brownbagger session. When asked why she was doing the presentation on the biological control of rangeland weeds Natalie said, "Biocontrol can provide an important contribution to rangeland health." If anyone was unable to attend Natalie's presentation they can get a recording at the USDA ARS, 1500 North Central Avenue, Sidney, MT 59270.