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Things to watch for during JuneFrom our experience of samples we have received during June in previous years in the OSU Plant Clinic, this page will highlight some problems that may occur this month. Abiotic disorders If June turns out to be hot, high temperatures may cause scorching of leaves due to sunburn, or sunscald. Symptoms show subsequently as stunted new growth, burned or brown lesions on foliage, necrotic areas on fruit and flowers. Click on images for more information
Bacterial disorders Cucurbits, including squash and cucumbers, often show symptoms of angular leaf spot caused by the bacterium Pseudomonas syringae pv. lachrymans. Irregularly shaped spots bounded by the veins occur on leaves. Stems and fruit may also be affected. This bacterium overwinters in diseased plant material and on seed and is then spread by rain, sprinker irrigation, as well as on hands and clothing. Click on images for more information
Viral disorders Look for recovery in blueberry already affected by Blueberry Shock Ilarvirus (BSIV). Bushes should produce new leaves and appear relatively normal as the season progresses, although they will not produce much fruit. If recovery does not happen then, although uncommon, Blueberry Scorch Virus (BBScV) may be present, with tip dieback and flower blight starting in a few branches and spreading to the entire bush over 1 - 3 years. Plant material should be tested to confirm the virus. Click on images for more information
We continue to see symptoms of Fall infection of Barley Yellow Dwarf Virus (BYDV) on grasses for seed as well as other cultivated and wild grasses with yellowing leaf tips (reddish in oats). BYDV is transmitted by several species of aphid. Click on image for more information
Fungal disordersWith warm and humid conditions promised for the early part of this month, watch out for powdery mildew which can affect a wide range of food and ornamental plants. Starting as small colonies on the undersides of leaves, these can rapidly spread in the right conditions. Click on images for more information
As with samples from April and May, the majority 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
see also "The Plant Clinic Year"
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June 1, 2009
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