Black Xylem Decline

Appears in
Oxford Companion to Wine

By Jancis Robinson

Published 2006

  • About

black xylem decline, a more formal name for the condition black goo. Unhealthy young vineyards have been studied in South Africa for about 50 years, and more recently have been a cause for concern in California, where rapid expansion took place in the 1980s. Similar problems have been noted in Europe, Australia, and New Zealand.

The reason is not clear, but the majority of evidence implicates wood-rotting fungi, perhaps associated with infected planting material. The fungus Phaeoacremonium has been isolated from unhealthy vines; when combined with other fungi Phellinus and/or Stereum species, it appears to cause esca. There is some evidence that black xylem decline may be overcome by treating planting material with hot water, which is also useful against nematodes, pierce’s disease, and phytoplasma disease.