Montana is not unfamiliar with the common invasive species known as whitetop (Lepidium drabae), also known as hoary cress. This noxious weed is prevalent throughout most of the west and has become quite a nuisance for local landowners. You might’ve read our previous article earlier this summer describing this weed, and if you did, I would like to give you a few updates on recent news and discoveries.
If you did not get a chance to read our previous article, whitetop is a flowering perennial species that creates clusters of small white flowers. When they are close to each other, they cluster even more to create a sea of this dense weed. It thrives in open areas with direct sun and can tolerate most soil types.
Here at the Whitehall Biological Weed Control Project, we work with a biological control agent called the whitetop gall mite (Aceria drabae). This mite specializes in creating galls (swellings) on the new flower buds and developing stems. It evolved to be host specific, which makes it completely dependent on whitetop for a food source.
