The Enemy - Buffalobur (Solanum rostratum) This is the only Idaho Noxious weed that is native to the United States but not to Idaho (as a plant native to Idaho cannot be listed as noxious). It is a short growing annual plant that has spines on the stems and seed heads. The yellow flowers develop a round seed that houses many seeds. This plant is recent to Eastern Idaho as it was brought to us by contaminated “wild bird” seed by a major retailer. The company that produces it in has been forbidden to ship any more bird seed into Idaho until they can prove that the seed is ‘Noxious weed Free’. The leaves from this plant are extremely lobed (like tomatoes – as they are in the same family) and have prominent yellow veins. Seeds can last quite a while as I have not had a bird feeder for 4 years and two plants popped up this year.
The Strategy - This plant has been known to be a host for the Colorado Potato beetle that eats up our commercially grown potatoes. It is also a very miserable plant to have around as the spines are very unforgiving and can keep wildlife, livestock, and recreationists from enjoying the environment. As this seed showed up in bird food we primarily find it near bird feeders, but have found it in pastures and ally ways – anywhere the birds fly or roost.
The Defense - As with all annuals, mechanical control is very useful. When digging it up just make sure that you get 2-3 inches of the root out of the ground and it will control the weed. Early in the spring you can use various herbicides such as 2,4-D , Banvel, or similar broadleaf herbicide. I do not recommend using Roundup as it is a non-selective herbicide and will also kill the surrounding grasses that are needed to keep other weeds from encroaching. If you suspect this plant is near your bird feeder (although the seed has not been allowed in Idaho for three years) call your local weed authority for proper identification and control.
U of I Idaho's Noxious Weeds Control Guidelines (183 KB PDF download)