Saturday, May 21, 2005
East facing wall with 1 foot overhang-to hard on HydrangeasWell this wall isn't going to cut it for the "Endless Summer" hydrangeas, as soon as the weather hit above 90 degrees, they are wilting...water is wicking away faster than the roots can absorb water. To help them get by, I make sure they are covered by 12 noon until 2pm when the overhang creates shade. I am drowning them in the morning, midday, and evening to keep them hydrated as possible, even the northwall hydrangea is wilting a little in full shade with two bushes around it to decrease wind. They are not acting like they are overwatered, although I am watching to see if there is any fungus developing on them from all the watering and humidity...
Anthracnose occurs sporadically in landscape and field plantings of bigleaf hydrangea. The causal fungus Colletotrichum gloeosporioides can attack both the leaves and the blooms of hydrangea. Hot, wet weather conditions appear to favor disease development. Heavily fertilized hydrangea may be most sensitive to attack by C. gloeosporioides.
At first, the brown spots are circular or slightly irregular in shape and somewhat sunken on fleshy leaves of hydrangea. The center of these spots may reach 1 inch or more in diameter and turn light brown to tan in color. Alternating dark and slightly lighter rings of dead tissue often give the spots a bull's-eye or a target-spot appearance (figure 3). When larger spots border midvein or other major veins in the leaf, they become distinctly more angular in shape. Under ideal conditions for disease development, large, dark brown, irregular blotches may spread across the leaves and flower petals (figure 4). Unlike Cercospora leaf spot, symptoms of anthracnose may appear almost simultaneously on leaves and blooms in the lower and upper region of the plant canopy.
The causal fungus C. gloeosporioides, which has a broad host range that includes a wide variety of commonly grown woody shrubs and trees, overwinters in fallen diseased leaves and other plant debris. Following several days of wet, overcast weather, masses of spores ooze from fruiting bodies (acervuli) embedded in leaf debris. These spores are spread to the leaves and bloom clusters primarily by splashing water. Penetration and colonization of host tissues occur most rapidly at temperatures of 75 to 90 degrees F. Frequent showers, dew, and prolonged periods of heavy fog increase the rate of infection and accelerate the appearance of symptoms. Diseased plants are the main source of anthracnose in landscape plantings of hydrangea.
Few options are available for controlling anthracnose on hydrangea. Taking cuttings from symptom-free plants will greatly reduce the risk of disease spread in container stock. Collecting fallen disease leaves and removing blighted blooms are also suggested. Since this disease appears to be more prevalent in large container or field plantings of intensively managed hydrangea, damaging outbreaks of this disease in residential landscapes are unlikely. Protective fungicide treatments, when applied at 10- to 14-day intervals during the summer, will protect vulnerable hydrangea from anthracnose.
Daconil Weather Stik 1.4 t. 1-3/8 pt. Apply when symptoms first appear on lower leaves and repeat every 10 to 14 days as needed. Use at shorter interval when disease is severe.
Daconil 2787 4F 2 t. 2 pt.
3336 50W 1 T 12-16 oz. Apply at first sign of disease on leaves and repeat every 10 to 14 days as needed. Use higher rate at shorter interval when disease is severe.
3336 4.5F --- 10-20 fl. oz.
Halt 50W 1 T ---
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