The Plant Disease Diagnostics Clinic (PDDC) typically charges a small fee for providing diagnoses of plant diseases and disorders. However, there are certain instances where the PDDC waives fees. In particular, if there are plant diseases that are new to the state and/or potentially have severe negative economic impacts to Wisconsin agriculture, the PDDC does not charge to provide a diagnosis. Early detection of new diseases can help in limiting and slowing spread, and may even provide opportunities to eradicate a disease. Early detection of established, but economically important, diseases can help provide growers critical information for disease management.
The following are diseases that the PDDC will be providing free diagnoses for in 2023.
This disease can have a huge impact on the commercial potato industry in Wisconsin (the third largest potato-producing state in the US). Identifying this disease as early as possible and determining which variant(s) of the pathogen (and there are many) has(have) arrived in the state are critical for providing timely and appropriate control recommendations to commercial potato producers. Because the disease can affect tomatoes as well as potatoes, I encourage home gardeners to watch for this disease in their vegetable gardens. If you see any suspicious leaf spotting on tomato or potato leaves or on tomato fruits, submit a sample for free testing. Just indicate when you submit that you are concerned about late blight.
This disease was first detected in Wisconsin in 2018 but has been devastating boxwood plantings in the eastern US since 2011. The PDDC is continuing to map the movement of boxwood blight in the state and added Door County to the official boxwood blight county map in 2022. If you see dark leaf spots, followed by leaf collapse and branch dieback on boxwood shrubs, get a sample to the clinic for a free diagnosis. The problem may just be winter burn, but if it is boxwood blight, I’d like to know.
I more commonly call this disease lipstick rust, and there is a move afoot to change the official name to red star rust (a literal translation of the original Japanese name of the disease). This disease is a new Gymnosporangium rust for Wisconsin, having first been reported in the state by WI DATCP in 2021. To date, lipstick rust has been confirmed in Dane, Kenosha, Milwaukee, Outagamie, Ozaukee, Portage, Racine, Sheboygan, and Waukesha Counties. Watch for the red or fuchsia-colored spots on apple and crabapple leaves characteristic of lipstick rust. If you see spots of this type, I suggest first submitting digital photos to the PDDC. If the symptoms look consistent with lipstick rust, and there has been an official confirmation of the disease in your county, I’ll make a diagnosis from the photos. If the symptoms look consistent, and there has not been an official confirmation of lipstick rust in your county, I’ll request that you submit a physical sample for DNA sequencing (the method of choice for confirming new cases of the disease). Either way, the diagnosis is free.