Downy Mildew on Sweet Woodruff (Galium odoratum)

Downy mildew (caused by a species of the oomycete, Peronospora) on the herb/groundcover Sweet Woodruff (Galium odoratum) was found on a recent sample. At first glance the symptoms suggested iron deficiency (based on yellow foliage and other indications by the grower). However, a closer look shows leaf dieback and gray lesions which indicate a pathogen may be involved. Flipping the leaves over (see photos below) reveals the characteristic fuzzy growth of downy mildew.

Downy mildew loves cool, wet conditions! Management should involve reducing leaf wetness (which is required for the spores to germinate). There has been no research done on fungicide control on Galium spp., so proceed with caution if choosing to use a fungicide. Test in small areas to ensure that phytotoxicity isn't going to be an issue. The Chase Research Gardens, Inc. out of California have done quite a bit of work on downy mildew fungicide control in ornamentals and some results can be found here.

Free Phytophthora online course

Are you interested in learning more about the disease Phytophthora and how it can affect your nursery?
Oregon State University and the Oregon Department of Agriculture have developed a FREE online course to help you identify and manage Phytophthora diseases in nurseries. This FREE course is also now offered in Spanish! The course is divided into three modules which take 60-90 mins each to complete.

If you're interested in receiving certification, OSU offers a Certificate of Mastery on Phytophthora from Oregon State University Extended Campus ($100 charge and online exam). But the information contained in the course is offered FREE! This is a great resource for nursery growers and I encourage you to check it out!

Pythium root rots of bean and watermelon seedlings

Today was a day of root rots! Two samples of pythium root rot but both came in with complaints of foliage problems on field transplants (browning and death of bean leaves & wilting of watermelon). Luckily, the submitters had included the full root system and soil so we were able to quickly make an accurate diagnosis. Pythium agar was used to confirm the presence of Pythium spp. Note the characteristic stem lesions.
Pythium root rot on snap bean transplants:

And Pythium root rot on watermelon transplants: