White mold on a bean plant. Photo: Howard Schwartz, http://www.growingproduce.com
A guest blog by Lucy Hope
Among the many possible strategies you can adopt to eliminate white mold in your garden, arguably the most important is never allowing it to grow in the first place. As noted in a study by scientists at Alberta’s Lethbridge Research Centre, white mold (or Sclerotinia sclerotiorum) is prevalent worldwide, and difficult to control. This is because when the spring and summer arise, the overwintering bodies of this species can germinate, releasing spores that can then infect damaged or old leaves. Keeping your garden is tip-top condition is arguably one of the most important steps you can take to keep the problem at bay.
Why Is White Mold So Sturdy?
White mold fungi form hard structures called sclerotia, which can survive in soil for over five years. In the spring and summer seasons, when temperatures hover between 51 and 68ºF (11-20ºC), they sprout into tiny mushrooms. These, in turn, produce spores that can travel large distances via the wind. Spores that land on damaged plant tissue can infect the plant, moving into the stem. The plant eventually dies, but new sclerotia are formed within the old tissue, and can survive in the soil, thus threatening other plants in turn.
What Does White Mold Look Like?
White mold looks fuzzy and almost cotton-like, and can be accompanied by tiny, dark sclerotia. It affects over 400 species of plants, and can therefore put the average garden plant at risk. The sclerotia themselves are small but easy to spot. They look a bit like a broken-off pencil tip, and are oblong or irregular in shape.
What Is – And What is Not – Sclerotinia sclerotiorum?
Before formulating a strategy to rid your home environment of mold, you need to differentiate between Sclerotinia sclerotiorum and other types of white mold. If you see a white growth on your garden shed doors, floors and other surfaces, it is a different species of mold that should be tackled by a professional. This is because white surface mold is harder to clean than typical black/green mold, which can easily be tackled with a mixture of vinegar and water. White mold on floorings and carpet may indicate that renovation is in order, though it is up to the professional to determine if these are salvageable. Sclerotinia sclerotiorum is limited to plants and garden produce, and should be treated in a very specific manner.
Ridding Your Garden of White Mold
To avoid white mold infecting your soil, choose plants that have an upright form, as they tend to dry more quickly than low-lying plants. Plants should have enough space and light between them, and drip or soaker hose systems should be used instead of sprinklers. If you spot any white mold, remove the infected plants immediately, using plastic sheets or barriers to ensure spores do not drop on adjacent plants while you are handling the infected plant. To be on the safe side, you might want to remove the soil beneath and immediately surrounding the plant, and replace it with new soil. Finally, consider filling your garden with very resistant plants, such as elephant ear, canna and ornamental reed or sedge. These are unlikely to provide white mold with the conditions it needs to thrive.
White mold is a prevalent problem in many gardens across the globe. To prevent its appearance in your garden, grow as many sturdy plant species as you can, and keep existing plants in optimal condition. Finally, be vigilant for signs of furry white moss and tiny black sclerotia, acting speedily if you spot these signs by quickly and cleanly disposing of the affected plant and (to be extra cautious) of the soil beneath it if possible.