Garden Talk: Fungal Diseases After A Cool, Wet Spring

Featured in this Show

• Cool Temps + Wet Conditions = Fungal Diseases In Garden

  Download

  A cool, wet Wisconsin spring has provided perfect conditions for a variety of fungal diseases to show up in gardens across the state.

  Garden fungal diseases range from the cosmetic to the more serious, with some that fall in between. Lisa Johnson, a Dane County University of Wisconsin Extension horticulture educator, said that some of the tomato diseases like septoria leaf spot and early blight can get out of hand quickly if not noticed early and tended to.

  “Those are soil-borne disease, so you can do some things with mulching to help prevent those,” she said.

  One of the first fungal diseases to appear in spring is anthracnose.

  “It attacks ash, oak and maple tress,” Johnson said. It is more cosmetic than really harmful, she said, “but it does tends to get people excited, and understandably so.”

  According to an article written by Brian Hudelson of the UW-Madison Plant Disease Diagnostic Lab, “Symptoms of anthracnose vary from host to host, but in general include irregular spots, and dead areas on leaves that often follow the veins of the leaves. Affected tissue can vary in color, but is often tan or brown. Severely affected leaves often curl and may fall off.”

  Some tree species, like sycamores, might drop twigs if they are infected, he wrote.

  Another common fungal disease is apple scab, which, despite the name, also affects pears and some other fruit trees that are part of the rose family. Fungal diseases on woody species like trees and shrubs tend to cause defoliation, she said, which is leaf loss.

  Powdery mildew reports are already coming in, Johnson shared. So far, it has made an appearance on monarda (also known as bee balm) and garden phlox.

  Cedar apple rust is also being reported, although clear symptoms have not yet emerged. According to the Plant Disease Diagnostic Lab, it affects “both junipers and woody rosaceous plants such as apple, crabapple, hawthorn and quince.”

  Telial horns are visible indicators of cedar apple rust. Johnson described them as “big, orange, globby structures that are on junipers. Those will produce spores that infect your hawthorns and your crab apples.”

  Johnson recommended removing the telial horns from junipers to hopefully prevent the disease’s spread.

  But an ounce of prevention is worth a pound of cure. Johnson said that choosing plant varieties that have some resistance to fungal diseases is a great place to start. Unfortunately, though, resistant doesn’t mean immune, she said: “So when we have a cool, wet year like this, you can still lend up with problems.”

  Proper spacing of plants can also help reduce fungal diseases. Johnson said that good air flow will help dry out the foliage and make the leaves a less hospitable environment. “A lot of them require wet foliage in order to have the spores actually germinate,” she said.

  Some of the fungal diseases can also overwinter, so fall garden clean-up is important for getting rid of any lingering spores. Johnson cautioned that a hot compost pile may kill the spores, “but if you’re a lazy composter like me — I don’t turn my pile very often, I don’t water it very often, I don’t fertilize it very often — it’s a good idea to get those leaves off of your property instead.”