Apple: Anthracnose and Bull’s-eye rot categories: Apple Apple Diseases Tree Fruits last review date: 2026-01-30 11:28 Apple anthracnose in early springPhoto 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 from this fungal group: […]
Apple: Bitter pit categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-02 02:15 Apple bitter pitPhoto 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 brown. The spots may […]
Apple: Burrknot categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-02 02:42 Apple burrknotPhoto 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 normal roots. Several apple […]
Apple: Crown and collar rot categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-04 01:06 Apple crown and collar rotPhoto 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 tissues and plant debris, […]
Apple: Crown gall categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-04 03:55 Large gall on crownPhoto 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 stems. Older galls are […]
Apple: Cytospora canker categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-04 04:25 Cytospora canker spore tendrils on apple twigPhoto 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 are small but enlarge […]
Apple: Fire blight categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-04 04:38 Fire blight infected leavesPhoto 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, appearing scorched. Canker can […]
Apple: Fruit russeting categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-04 04:49 Severe russetingPhoto 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 mildew infections, and some […]
Apple: Nectria canker (European canker) categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-06 02:44 Mature European canker on branchPhoto 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 through leaf scars and […]
Apple: Nectria twig blight (Coral spot) categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-10 09:44 Nectria twig blightPhoto 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 small branches. Cankers are […]
Apple: Perennial canker (Bull’s-eye rot) categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-10 10:09 Apple bull’s eye rotPhoto 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 a sunken canker surrounded […]
Apple: Phytophthora fruit rot categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-10 10:24 Phytophthora fruit rotPhoto 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 or when overhead watering […]
Apple: Powdery mildew categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-10 10:52 Powdery mildew on apple foliagePhoto 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 terminal may become covered […]
Apple: Scab categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-10 11:24 Apple scab on fruitPhoto 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, pale, chlorotic, water-soaked spots […]
Apple: Virus diseases categories: Apple Apple Diseases Tree Fruits last review date: 2026-02-10 11:56 Apple mosaic virus foliar symptomsPhoto 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 common virus problems is […]