Apple: Anthracnose and Bull’s-eye rot Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-08-28 02:29 Last edit date: Apple anthracnose in early spring Photo by: R.S. Byther Biology Apple anthracnose is a fungal disease that impacts apple production in regions with mild year-round temperatures, abundant winter rains, and cool-humid summers. Two disease problems result […]
Apple: Bitter pit Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-02-02 02:15 Last edit date: Apple bitter pit Photo by: C.R. Foss Biology Bitter pit of apples is a physiological problem which results from calcium deficiency in the fruit. Depressed spots appear on the fruit surface and the tissue beneath the spot becomes […]
Apple: Burrknot Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-02-02 02:42 Last edit date: Apple burrknot Photo by: C.R. Foss Biology Burrknot of apples is a physiological problem which appears as a growth somewhat resembling crown gall. The roughened, warty-looking growth is comprised of root tissues. If buried with soil, burrknots may produce […]
Apple: Crown and collar rot Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-02-04 01:06 Last edit date: Apple crown and collar rot Photo by: J.W. Pscheidt Biology Crown rot of the rootstock and collar rot of the scion wood of apple trees is caused by a soilborne fungus. It can survive in infected […]
Apple: Crown gall Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-02-04 03:55 Last edit date: Large gall on crown Photo by: R.S. Byther Biology Crown gall is caused by a soilborne bacterium. The bacteria infect through wounds on the crown and roots. Young galls are fleshy, white, enlarged masses on the roots or […]
Apple: Cytospora canker Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-02-04 04:25 Last edit date: Cytospora canker spore tendrils on apple twig Photo by: R.S. Byther Biology The fungi which cause Cytospora canker attack through wounds on twigs and branches. The disease can spread to healthy tissues after the initial infection. Initial cankers […]
Apple: Fire blight Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-02-04 04:38 Last edit date: Fire blight infected leaves Photo by: G.G. Grove Biology Fire blight is a bacterial infection which typically attacks via wounds or blossoms. Initially, twigs and flowers appear water soaked. Infected tissues quickly turn brown to black and die, […]
Apple: Fruit russeting Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-02-04 04:49 Last edit date: Severe russeting Photo by: R.S. Byther Biology Russetting is the appearance of corky, roughened, brownish or grayish areas on apple fruits. There are several possible causes for fruit russeting, including cool wet weather, frost damage, spray damage, powdery […]
Apple: Nectria canker (European canker) Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-08-28 02:29 Last edit date: Mature European canker on branch Photo by: R.S. Byther Biology Nectria (European) canker is a fungal disease affecting the twigs and branches of apple and pear. The fungus infects during rainy weather in the fall, attacking […]
Apple: Nectria twig blight (Coral spot) Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-02-10 09:44 Last edit date: Nectria twig blight Photo by: C.R. Foss Biology Nectria twig blight is caused by a fungus which invades plant tissues through wounds and natural openings in the bark. The infections typically occur on twigs and […]
Apple: Perennial canker (Bull’s-eye rot) Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-02-10 10:09 Last edit date: Apple bull’s eye rot Photo by: G.G. Grove Biology Perennial canker is a fungal disease. It is similar to anthracnose but occurs primarily east of the Cascades in Washington. The characteristic symptom of perennial canker is […]
Apple: Phytophthora fruit rot Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-02-10 10:24 Last edit date: Phytophthora fruit rot Photo by: G.G. Grove Biology Phytophthora fruit rot is caused by a soilborne fungus which can also be found in and carried by irrigation water. Infection occurs when water contacts fruit on low-hanging limbs […]
Apple: Powdery mildew Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-02-10 10:52 Last edit date: Powdery mildew on apple foliage Photo by: M. Bush Biology Powdery mildew of apple is a fungal disease found on twigs, leaves, blossoms, and fruit. New growth is particularly susceptible, since the fungus overwinters in buds. The entire […]
Apple: Scab Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-02-10 11:24 Last edit date: Apple scab on fruit Photo by: R.S. Byther Biology Apple scab is caused by a fungus which also causes scab on crabapple and hawthorn. The first infections occur during wet weather in the spring. Initially, the disease causes tiny, […]
Apple: Virus diseases Categories: Apple Apple Diseases Tree Fruits Last review date: 2026-02-10 11:56 Last edit date: Apple mosaic virus foliar symptoms Photo by: R.S. Byther Biology Virus diseases of apples are rarely significant problems in home orchards. Symptoms are most commonly seen as bark disorders, leaf mottling, or misshapen fruit. One of the more […]
Apple: Aphids Categories: Apple Apple Insects Tree Fruits Last review date: 2026-09-29 06:57 Last edit date: Rosy apple aphids Photo by: R.S. Byther Biology Three aphids are important pests of apple. Green apple aphids feed throughout the growing season on terminals, causing twisted and deformed leaves and stunted shoots. They produce honeydew, a sweet, sticky […]
Apple: Apple ermine moth Categories: Apple Apple Insects Tree Fruits Last review date: 2026-09-29 06:57 Last edit date: Apple ermine moth Photo by: A.L. Antonelli Biology The apple ermine moth is an imported pest which feeds exclusively on apples. The adult moth has silver-white wings spotted with black. Larvae are gray, cream-colored, or greenish with […]
Apple: Apple maggot Categories: Apple Apple Insects Tree Fruits Last review date: 2026-09-28 06:57 Last edit date: Apple maggot tunneling Photo by: M. Bush Biology The apple maggot is potentially a serious pest of apples. Transportation of home-grown fruit from infested to non-infested areas is prohibited in Washington. The adult apple maggot is a small […]
Apple: Apple-and-thorn skeletonizer Categories: Apple Apple Insects Tree Fruits Last review date: 2026-08-29 06:40 Last edit date: Apple-and-thorn skeletonizer caterpillar feeding on leaf Photo by: A.L. Antonelli Biology The adult of the apple-and-thorn skeletonizer is a small dark-brown or reddish-brown moth. It overwinters as a pupa or an adult, with the females laying eggs in […]
Apple: Brown marmorated stink bug Categories: Apple Apple Insects Tree Fruits Last review date: 2026-09-29 06:57 Last edit date: Brown marmorated stink bug damage to apple fruit Photo by: D. Pfeiffer, Virginia Tech Biology The brown marmorated stink bug (BMSB) is an introduced pest species from Asia that is spreading quickly across the United States. […]