This plant suddenly scorched after after a small amount of rain. This was the first rain since fertilizer has been applied too heavily to the base of the bush.
Flowers are turning water soaked, brown and the fuzzy sporulation of Botrytis is developing.
Lisa Jones, 2015.
Botrytis readily colonizes dead tissue as seen on this spent lilac flower.
Lisa Jones, 2015.
Cause Pseudomonas syringae pv. syringae, the bacterium that also causes bacterial blight of pear, blueberry, cherry, maple, and many other woody plants. Losses can be substantial due to this disease in nursery production. Older landscape plantings can still thrive despite high disease pressure. Bacteria overwinter on diseased twigs or as epiphytes on healthy wood. Factors that weaken or injure plants predispose them to disease.
When shoots begin to die they tip over in what is called a Shepard's crook symptom.
Jay W. Pscheidt, 2011.
Buds may fail to open in the spring and turn necrotic.
Jay W. Pscheidt, 2011.
Water-soaking is a common first symptom of bacterial blight on lilac.
Jay W. Pscheidt, 2011.
Purple cultivars get the disease too!
Jay W. Pscheidt, 2011.
Many shoot and leaves can be blighted in the garden.
Jay W. Pscheidt, 2011.
Lilac grown outside in nursery settings can have a problem with bacterial blight.
Jay W. Pscheidt, 1990's.
Leaf spots and flower blight can be seen in this image.
Note the red blotches on the top side of the leaves.
Photo by Jay W. Pscheidt, 1999.
Note the fuzzy, white growth on underside of this leaf.
Photo by Jay W. Pscheidt, 1999.
Cause Beet western yellows virus is an increasingly significant pathogen in western Oregon. The principal vector is the green peach aphid, Myzus persicae, although other aphid vectors are likely. After acquiring the virus from infected plants, aphids may retain for life the ability to transmit virus. An enormous number of crop and weed species are susceptible to the virus; thus the natural inoculum reservoir is hardly avoidable.
Oldest leaves turn yellow prematurely, typically beginning at the margins and progressing in; veins and midribs tend to remain green.
Melodie Putnam, 1992.
Cause The aster yellows phytoplasma is transmitted by several leafhoppers and has a very wide host range.
Cause A bacterium, Pseudomonas cichorii, which can survive in soil for some time after the lettuce crop is removed.
Symptoms Dark-brown, firm, necrotic spots a few millimeters in diameter occur on leaves and petioles of lettuce several layers within the lettuce head. Because outer layers of leaves are rarely affected, usually it is impossible to detect the disease without destroying the head.
Cause Physiological disorder. All varieties grown in the Pacific Northwest are susceptible to some degree, but they differ considerably. Under Oregon conditions, all California varieties are susceptible. At least five environmental conditions-all of which affect the plant's calcium uptake or distribution-reportedly favor development of the disorder. (1) High relative humidity with high temperatures, particularly nights above 65°F during head development.
Cause Unknown but believed to be physiological. Tests have not associated red rib with soil types, pH, or fertilizing practices.
Cause Lettuce mosaic virus, which is transmitted by seed and by the green peach aphid.
Symptoms In young plants, first the seedling leaves roll up on the long axis and the first true leaf is irregularly shaped and slightly lobed. Vein clearing and bronzing follow. Bronzing is caused by necrotic flecking of the leaf blade, especially along the veinlets. Symptom expression varies with variety and climatic factors.
