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Diseases of African sumac ( Rhus lancea ) in Arizona

Cotton (Texas) root rot

African sumac (Rhus lancea) is a native of Africa. It is very heat tolerant and grows moderately fast in the low desert. However, it is susceptible to Cotton (Texas) root rot caused by the soil borne fungus, Phymatotrichopsis omnivora. Infected trees may live for months or a year or more, declining slowly with loss of foliage density and some yellowing leaves. Trees often die suddenly in late spring through early fall when rotted roots can no longer keep up with transpiration demands. Leaves remain attached to the tree, and most roots are entirely rotted at this point.

Mycelial strands of the fungus are usually easy to find on the roots (photo 1); cross-shaped hyphae may be visible under the microscope (photo 2). However, it is very important to have a confirmed diagnosis of cotton root rot made by a qualified expert. The site should be replanted only with a very tolerant or immune species. For more information see the bulletin on cotton root rot:
   http://ag.arizona.edu/pubs/diseases/az1150.pdf

Links for more Information:
  http://ag.arizona.edu/pubs/diseases/az1124/#prr
  http://ag.arizona.edu/pubs/diseases/az1150.pdf
  http://cals.arizona.edu/pima/gardening/aridplants/Rhus_lancea.html

   1 tan mycelial strands of cotton (Texas) root rot 2 cross-shaped hyphae of cotton (Texas) root rot

 



August 7, 2013