Verticillium Wilt

• Verticillium wilt, caused by fungi of the Verticillium genus, is the most damaging disease that impacts boxelder. Leaves turn faded green, yellow or brown and may wilt. Newly infected branches may exhibit dark stains under peeled-back bark. Branches wilt and die, generally beginning on one side of the tree. The entire tree can eventually die. Use proper cultural practices including irrigation and fertilization to improve the boxelder's chance for survival. Prune out any dead branches; severely affected trees may be hazardous and require removal. If Verticillium wilt has been present in an area, plant only resistant species.
  
  

Leaf Spot Diseases

• Fungi can infect box elder, causing leaf spots to develop. Spots may be either discreet dots or large patches that encompass entire leaves; some defoliation may occur if the infection is severe. Avoid the presence of these fungi by limiting overhead irrigation and watering in early morning. Remove fallen leaves and debris regularly. Fungicides can be used to address leaf spots but are generally not warranted.
  
  

Wetwood

• Wetwood, also known as slime flux, is caused by bacteria or yeast organisms. Boxelders that wetwood affect have stained wood areas that excrete fluids. Severely infected trees may suffer wilt and dieback. If an infection occurs, drill a 1/4-inch hole several inches into the tree until fluid begins to exit the wound, and install a copper tube in the hole. Regularly check the tube, which serves to drain excess fluid and gases, to ensure that it doesn't become plugged.
  
  

Stem Canker

• Boxelder may develop stem cankers, which the Eutypella parasitica fungus causes. Cankers are irregularly shaped and contain raised rings of callus tissue attached to the wood by white to brown fungal tissue; older cankers may develop small black fungal tissue in the center. To prevent stem cankers, remove dead branches promptly. Small cankers can be removed.
  
  

Root Rots

• Boxelder can suffer from root rots caused by Phymatotrichum omnivormum or Rhizoctonia crocorum fungi. Both of these pathogens are most active and damaging when the soil is warm and conditions are dry. The leaves of infected trees become dry and brown and remain attached to the tree. Affected trees may not recover, especially if the tree is stressed and root damage is extensive. Ensure that the tree is receiving adequate water; and, while the tree is still showing slight symptoms, cut back about half of the top growth to compensate for the root loss. These fungi can remain in the soil for years, so plant only resistant plants in the area following an infection.