Many factors come into play when planning to grow blueberries. The following factors must be taken into consideration:
- purchasing plants from a reliable source
- planting recommended cultivars
- planting correctly on raised beds in the full sun
- controlling weeds
- pruning correctly
These steps are extremely important for growing plants and can also help prevent pest problems. Disease can be among one of the biggest problems when growing this plant. Below are three common diseases that affect blueberries, as well as management information.
Mummy berry has been a problem for years, but in recent years there have been an increasing number of calls about the disease. Growers may notice the disease when little stems near the bloom or fruit start to wilt and die. There are other blights that cause the small stems to die, but when the developing fruit starts to shrivel up and harden, mummy berry is the cause. This disease overwinters on the ground where infected berries fell from the year before.
Mummy berry is commonly spread from one farm to another with shared harvesting equipment, but it can be common in home plantings as well. The disease is spread from the infected fruit to the plant through the bloom. The disease likes low, wet areas, so choosing the right planting site and using raised beds will help prevent.
Raking out/removing infected fruit is beneficial but can be time consuming on a large scale. Adding mulch and covering the infected fruit can also help. Fungicides can be used early in the spring as well. Spraying fungicide a few times while the plant is blooming can help.
Phytophthora Root Rot
Phytophthora root rot can be a serious problem in low lying areas. Years ago, it was common to plant rabbiteye plants at ground level and plant southern highbush on mounds, as southern highbush are very susceptible to phytophthora root rot. Now, this disease is common.
Before planting any blueberry plants, build a mound for the new plant and stay away from low areas. The disease will attack the roots, but the first symptom will be yellowing leaves. The leaves will eventually drop from the plant and the stems will begin to die as well. Improving drainage or planting in another location may be the best way to manage the disease.
Botryosphaeria Stem Blight
Botryosphaeria stem blight is the number one problem seen on blueberry farms as well as home plantings. Dark brown to black branches that will eventually girdle the stem and cause dieback. When cutting into the infected stem, brown discoloration inside the stem will be visible.
Blueberry is an easy plant to root, but do not take cuttings from infected plants. The death rate for young infected plants is high, and planting disease free plants is extremely important. Older plants do suffer and the growth rate is reduced, but mortality is not as bad. The disease enters the plant through wounds from mechanical harvesters or pruning. Take care not to spread the disease from one plant to another when pruning. It takes time, but it is important to clean pruners as often as possible with a 10% bleach solution or by using rubbing alcohol.
This disease is not active in cold weather, so pruning diseased branches in the winter is highly recommended. This disease is also stress related so make sure plants are planted correctly in the proper place, with irrigation, mulch, and manageable weeds. Fungicides are mostly ineffective in managing this disease, but some fungicides have helped when sprayed directly after pruning.
Sometimes descriptions are not helpful in diagnosing a plant disease. Extension has plant pathology labs in Birmingham, Auburn, and Mobile. Send samples of plant tissues to get professional help diagnosing the disease. Depending on the tests that are conducted, it may cost between $15 and $30. For help sending samples or answering questions—about these or any other pests associated with blueberries—contact your county Extension office.