Sclerotinia Stem Rot (Timber Rot) Widely Reported

Sclerotinia timber rot has been widely reported on high tunnel tomato this year, and has been found on tobacco and cucumber in greenhouse systems. It also occurs on peppers and ornamentals.

Like Pythium, Sclerotinia is benefited by wet weather and moderate (50° to 70°F) temperatures. Because of this, Sclerotinia usually only produces spores at the beginning of the season, which may be blown into tunnels or greenhouses by wind. Although it does not produce secondary spores, Sclerotinia is important because it may infect many crops and because its sclerotia (hardened balls of fungal mycelium) may survive in a dormant state for up to 7 years in soil.

Figure 1. (A) Sclerotia (hardened orbs of fungal mycelium) may be found inside or outside infected tomato stems. These may survive up to 7 years in soil. (B) Timber rot lesions often originate at clips or trellis sites, since Sclerotinia requires a wound to infect plants. (C) Sclerotinia may also infect fruit near the calyx, or plant-side, of fruit. (Photo: Emily Pfeufer, UK)

Figure 1. (A) Sclerotia (hardened orbs of fungal mycelium) may be found inside or outside infected tomato stems. These may survive up to 7 years in soil. (B) Timber rot lesions often originate at clips or trellis sites, since Sclerotinia requires a wound to infect plants. (C) Sclerotinia may also infect fruit near the calyx, or plant-side, of fruit. (Photo: Emily Pfeufer, UK)

Figure 2. Sclerotia developing in infected tomato fruit that has fallen on fabric in a greenhouse (Photo: Emily Pfeufer, UK)

Figure 2. Sclerotia developing in infected tomato fruit that has fallen on fabric in a greenhouse. (Photo: Emily Pfeufer, UK)

Disease Management Approaches

Preventing the introduction of Sclerotinia

  • Completely remove previously infected plants and plant debris from field or high tunnel area.
  • Sweep fabric floor to remove any sclerotia and disinfest using 10% bleach.
  • Keep area around high tunnel free of broadleaf weeds.
  • Ensure adequate fungicide spray coverage of stems.

Management when Sclerotinia is identified

  • Remove from area by carefully digging up entire infected plant, bagging, and disposing far away (at least 500 feet) from areas that will be cropped with susceptible plants.
  • In greenhouse or high tunnel, protectant sprays with mancozeb may prevent Sclerotinia infections, and Fontelis used for Botrytis management may have some activity.
  • In the field, Cabrio or Priaxor are labeled for management of Sclerotinia.

 

By Emily Pfeufer, Extension Plant Pathologist

 

 

Posted in Vegetables