Walnut: Anthracnose (Blotch) Categories: Tree Fruits Walnut Walnut Diseases Last review date: 2026-08-28 02:29 Last edit date: Walnut anthracnose infection on leaf Photo by: R.S. Byther Biology Anthracnose or blotch of walnut is caused by a fungus. The disease affects leaves, young twigs, and nuts. Leaves develop irregularly circular reddish-brown to grayish-brown spots up to […]
Walnut: Blackline Categories: Tree Fruits Walnut Walnut Diseases Last review date: 2025-08-23 12:21 Last edit date: Walnut with bark cracks and blackline at graft union Photo by: J. W. Pscheidt Biology Blackline is a viral disease of English walnut (Juglans regia). It causes death of water-conducting tissues at the graft union. Initially, infected trees show […]
Walnut: Blight Categories: Tree Fruits Walnut Walnut Diseases Last review date: 2026-08-28 02:29 Last edit date: Walnut blight symptoms on husks Photo by: R.S. Byther Biology Walnut blight is a bacterial disease affecting leaves, nuts, and other new growth including flowers. Bacteria are spread to new growth in the spring by rainy weather during the […]
Walnut: Thousand cankers disease Categories: Tree Fruits Walnut Walnut Diseases Last review date: 2025-08-23 12:29 Last edit date: Biology Thousand cankers disease (TCD) of walnut is a fungal disease associated with and spread by walnut twig beetles (WTB). Beetles feed on both healthy and damaged trees but injured or weakened trees are more susceptible to […]
Walnut: European fruit lecanium Categories: Tree Fruits Walnut Walnut Insects Last review date: 2026-08-29 09:14 Last edit date: Lecanium scales on twig Photo by: R.S. Byther Biology The European fruit lecanium is a shiny brown scale insect found on twigs. Adults are 1⁄8″ to 1⁄4″ in diameter and roughly turtle shaped. They may have light […]
Walnut: Walnut aphid Categories: Tree Fruits Walnut Walnut Insects Last review date: 2026-08-29 09:24 Last edit date: Green peach aphid closeup Photo by: Unknown Biology Walnut aphids are small, pale yellow, pear-shaped insects. They are typically found on the undersides of leaves. A second aphid species common on walnuts is the dusky-veined aphid, a grayish […]
Walnut: Walnut blister mite Categories: Tree Fruits Walnut Walnut Insects Last review date: 2025-08-23 12:34 Last edit date: Walnut blister mite damage Photo by: R.S. Byther Biology The walnut blister mite is an eriophyid mite. These tiny, whitish, sausage-shaped mites cause raised green to yellowish blisters on the upper leaf surfaces. Beneath the blister, on […]
Walnut: Walnut husk fly Categories: Tree Fruits Walnut Walnut Insects Last review date: 2026-09-29 06:57 Last edit date: Walnut husk fly damage Photo by: A.L. Antonelli Biology Adult walnut husk flies are slightly smaller than a house fly. They are brown with a yellow mark on the back, and the otherwise clear wings are marked […]
Walnut: Walnut twig beetle Categories: Tree Fruits Walnut Walnut Insects Last review date: 2025-08-23 05:01 Last edit date: Walnut twig beetle adult Photo by: S. Valley, ODA Biology The walnut twig beetle (WTB) is a small bark-boring beetle (Pityophthorus juglandis) believed to be native to the southwestern US. Not a great deal is known about […]