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Things to watch for during AprilFrom our experience of samples we have received during April in previous years in the OSU Plant Clinic, this page will highlight some problems that may occur this month. Viral disordersSymptoms of Fall infection of Barley Yellow Dwarf Virus (BYDV) on fescue, rye, wheat and many other cultivated and wild grasses may first appear in the spring as yellowish leaf tips (reddish in oats). BYDV is transmitted by several species of aphid. Click on the image for more information
Later in the month Blueberry Shock Ilarvirus (BSIV) may become apparent if flowers and young shoots suddenly die when the flowers are about to open. Entire bushes or parts of branches may show symptoms as a shock reaction to this viral infection transmitted in pollen by bees and other pollinators. NEW UPDATEThe warm weather this last weekend (4/12/08) brought on a lot of symptoms of blueberry shock. The symptoms we are seeing are dead buds on green stems. The bacterial problem Pseudomonas syringae can look similar but for those usually we see dead buds on dead shoot tips. Click on the images for more information
Bacterial disorders Damage caused by species of Pseudomonas including Pseudomonas syringae, on woody ornamentals are typically seen at this time of year particularly in variable weather conditions and are especially favored by frosty mornings followed by moist or wet conditions. These bacteria overwinter in diseased twigs or as epiphytes on healthy wood. Tissues that have suffered injury from pruning, frost, unsuitable soil pH, poor nutrition, or infection by other pathogens, are predisposed to Pseudomonas diseases and exhibit a variety of symptoms. Click on images for more information Fungal disordersOften at this time of year, nearly half of the fungal diseases we receive on samples of woody ornamentals are due to species of Phytophthora. Symptoms may occur both above and below ground including root rot, branch dieback, stem canker and are associated with poor drainage. Jay Pscheidt discusses symptoms, detection and management of Phytophthora diseases in his PNW Plant Disease Management Handbook article. Click on image for more information UPDATEMany apothecia of Blueberry Mummyberry were found 4/7/2008. Some looked a bit old though none were found the previous Monday. This indicates they started coming out about during the first week of April with a big flush the first weekend. The primary symptoms of this disease could be expected to show up later this month as the plants begin to flower. Abiotic disordersSudden low temperatures during spring can injure new growth on plants, or young plants that have not fully hardened off. An excellent discussion of Winter Injury in Landscape Plants can be found in the PNW Plant Disease Management Handbook. Click on images for more information |
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August 28, 2008
