Blueberry shrubs (Vaccinium spp.) can fall prey to various insects and diseases that may cause serious damage or even death. They are generally hardy in U.S. Department of Agriculture plant hardiness zones 3 to 9, although this varies by variety. Red, splitting leaves in the spring can be caused by a disease or exposure to chemicals. The shrubs can survive one of these but will not survive the other.
This Fungi is not Funny
Phytophthora root rot can cause blueberry shrub leaves to turn red and split in the spring. The fungi that cause it spread more prolifically during the early spring and in late fall when the weather is cool and rainy. The symptoms, however, do not usually occur until the shrub is stressed from lack of water. Additional symptoms are dull green, purple or yellow leaves and leaf wilting. Bark on the base of the stems at the soil line is darker, appearing wet or waterlogged. If the bark is scraped away, the wood below will be reddish-brown. The roots turn black or brown.
Will it Ever Leave?
There is nothing to be done for blueberry shrubs with phytophthora root rot. As the disease progresses, surviving branches and leaves will be stunted, the shrub will drop its leaves, branches and canes will die back and eventually the whole shrub will die. It may die quickly or last for a few years. The fungus will continue to live on in the soil, even after the blueberry shrub has died and been removed. Do not plant a new blueberry shrub or any other type of plant in the same spot if it is susceptible to phytophthora root rot.
Watch Where You’re Spraying That
Herbicides can cause serious damage to blueberry shrubs. In addition to red and splitting leaves in the spring, the leaves may curl, have dead spots and become elongated or strap-shaped and new growth on the entire shrub may be stunted. Branches and canes may die, blooming may be delayed and witch’s broom may occur, which is an odd grouping of deformed twigs at the ends of branches. Herbicides containing glyphosate, dicamba or 2,4-D are a few of the many herbicides that can cause this damage. The damage may become evident immediately after exposure but may not appear until the spring following a fall herbicide application.
A Little TLC will Make it Better
Blueberry shrubs will usually survive herbicide exposure, although the red, splitting leaves and other symptoms may be present for several years. Supplemental water and fertilizer will help the shrub recover. Give mature blueberry shrubs 4 to 6 gallons of water each day, as long as the soil drains quickly, and 8 gallons when they have berries. Reduce the frequency of watering if the soil stays too wet for too long. The soil should be moist, not muddy. Spreading a 2- to 3-inch layer of mulch around the shrub will help keep the soil moist. Fertilize the shrub in early spring and late spring with 10-10-10 or 7-7-7 fertilizer that contains potassium sulfate or ammonium sulfate. Sprinkle 1/4 cup of fertilizer around the shrub if it seems to be growing quickly or up to 1 1/2 cups if it is growing slowly.
- University of Illinois Extension: Small Fruit -- Blueberry
- Floridata: Vaccinium Ashei
- Virginia Cooperative Extension: Specialty Crop Profile -- Blueberries
- Missouri Botanical Garden: Phytophthora Root Rot of Trees and Shrubs
- The Ohio State University Extension: Organic Small Fruit Disease Management Guidelines
- Missouri Botanical Garden: Herbicide Damage to Plants
- University of Nebraska, Lincoln: Effects of Glyphosate on Highbush Blueberry
- University of Connecticut Soil Nutrient Analysis Laboratory: Suggested Fertilizer Practices for Blueberries
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