CONSERVATION -- Vehicles can pick up large numbers of seeds from weeds and other plants and spread them for miles, especially when the vehicles are driven off-trail and under wet conditions.

This factor in the spread of noxious weeks is documented in a story in a new Montana State University Extension publication describing field studies that measure the extent to which vehicles pick up and disperse weed seeds.

Some of the findings include:

• Wet conditions promote weed attachment to vehicles.
• ATVs picked up large numbers of seeds. In the fall, up to 5,500 seeds per mile were picked up off-trail compared to about 400 seeds per mile on-trail. The number of seeds picked up in spring was much lower.
• Tracked vehicles picked up more seeds than wheeled vehicles.
• Up to 99 percent of seeds stayed attached to a truck after traveling 160 miles under dry conditions, but seed retention was much lower after traveling long distances under wet conditions.
• However, if seeds are picked up in mud, which then dries on the vehicle, they can travel almost indefinitely until it rains or the road surface is wet, allowing for extremely long distance transport of seeds.

The researchrs say preventing the spread of weeds into non-infested areas is the most effective and efficient way to manage weeds over the long term.

To help prevent the spread of weeds, washing vehicles frequently is beneficial with particular concentration on wheel wells. Washing vehicles is especially important before and after driving on roads with high densities of weeds along the edges or after driving off-road or trail.