I have been asked whether it is true that some weeds can increase the prevalence of certain diseases.
Yes, it is true, which is why it can be especially important to control these species.
Henbit, purple deadnettle and stinkweed (field pennycress) are alternate hosts for soybean cyst nematode (SCN) and should be controlled. A study conducted in Indiana found that the longer henbit and purple deadnettle were allowed to grow in the fall, the higher the soybean cyst nematode population densities (1).
To stay on top of these pests, make sure you download the “pestmanager” app. A new version was to be released in March that includes photos and Integrated Pest Management (IPM) strategies for insects and diseases in field crops. Go to pestmanager.ca to download the app on your Apple, Android or BB10 device.
(1) J. E. Creech, J. Faghihi, V. R. Ferris, A. Westphal, and W.G. Johnson 2007. Influence of intraspecific henbit (Lamium amplexicaule) and purple deadnettle (Lamium purpureum) competition on soybean cyst nematode (Heterodera glycines) reproduction. Weed Sci. 55:665-670.