A worker manually applies fungicide, imbued with blue dye, to a freshly cut tree stump to fight the spread of fungal diseases such as Heterobasidion root disease. / Photo Credit: Wisconsin DNR

By Kyoko Scanlon, DNR Forest Pathologist, Fitchburg
Kyoko.Scanlon@wisconsin.gov

The manufacturer, Lallemand Plant Care, recently decided to remove Rotstop® C fungicide from the North American market.

As a result, the product is no longer available for purchase in North America. If you already have the product and have stored it in an appropriate space, you may still use it as a preventative treatment for Heterobasidion root disease (HRD) as long as the expiration date has not arrived.

Although you may still find ordering information for Rotstop® C online, the information is out of date.

HRD is a serious disease of conifers that causes reduced height, shoot and diameter growth, along with thin, yellowish/red foliage, ultimately causing mortality.

Once HRD exists in a stand, it is very difficult to control. Prevention is the best approach. Preventive pesticide treatments can be applied to fresh cut stumps at the time of harvest to protect them.

Many factors influence the risk of infection and impact by HRD. A risk-based fungicide treatment guide is available for landowners and property managers to determine whether fungicide treatment is warranted in a stand.

Rotstop® C, a biological fungicide that contains spores of a naturally occurring fungus, became available in 2016 as an alternative to a borate-based chemical, Cellu-Treat®. Cellu-Treat® is still available to protect fresh cut stumps from HRD in Wisconsin.

With the discontinuation of Rotstop® C, Cellu-Treat® is the only pesticide registered and currently available for use to prevent HRD in Wisconsin. The Heterobasidion root disease fact sheet provides information about how to purchase Cellu-Treat®.