English Walnut Tree Diseases


The English walnut tree is from the family Juglandaceae and is a fast-growing tree that reaches a height of 40 to 60 feet. The root stock is often grafted from the black walnut tree. English walnuts grow well in full sun and light, loam-type soils.

Fungal Disease

Leaf blotch creates brown spots on the nuts and leaves, causing them to fall from the tree. Root rot affects the roots, causing the tree to become stunted and the lower leaves to turn yellow and discolored.

Fungal Treatment

Leaf blotch is treated by removing and destroying infected leaves and nuts and applying a fungicide that contains hydrated lime and copper sulfate. Removing the trees is the only solution to root rot, as the roots are destroyed and the tree will never recover.

Bacterial Disease

Walnut blight produces black spots on the leaves with spots and holes in the nuts. Crown gall creates a gall or ball on the main stem of the tree.

Bacterial Treatment

Walnut blight is treated by pruning and destroying affected areas and applying powdered copper sulfate. Treat crown gall by removing young trees and painting the gall on older trees with a commercially purchased gall treatment made from a natural strain of Agrobacterium radiobacter. This bacteria is a close relative to the crown gall bacteria and blocks it from entering the tree.

Viral Disease

Blackline is a disease that kills the tops of the trees and causes shoots to grow from the roots. The virus spreads quickly as it is carried by infected grafts, seed and pollen.

Viral Treatment

Complete removal of the tree top is required to control blackline; there is no treatment. Start a new canopy by developing several suckers on the tree.


  • Canopy Tree Library
  • Diseases of Shade and Ornamental Trees
  • How to Grow English Walnuts
Keywords: English walnut tree, crown gall, leaf blotch

About this Author

Jennifer Loucks has been writing since 1998. She previously worked as a technical writer for a software development company, creating software documentation, help documents and training curriculum. She now writes hobby-based articles on cooking, gardening, sewing and running. Loucks also trains for full marathons, half-marathons and shorter distance running. She holds a Bachelor of Science in animal science and business from University of Wisconsin-River Falls.