We may be a few months out from planting brambles, but it is never too early to discover what common bramble disease symptoms you need to watch out for! To protect your crop, early detection of plant diseases is crucial.
You might be thinking, what is a bramble? Brambles are bush-like plants with arching canes in the Rubus family of plants. The Rubus family includes blackberries and raspberries (including red, black, and yellow). Bramble roots are perennial, and bramble canes are biennial.
What is a pathogen?
A pathogen is an organism causing disease to its host. Bacteria, viruses, nematodes, and fungi are pathogens that can cause plant diseases. Pathogens enter their host and seize the plant’s energy for their use. Pathogens can enter a plant in various ways, including wounds or natural openings, penetrating plant tissue, mechanical damage, or insect transmission.
What is a disease cycle?
A disease cycle is a series of events involved in disease development. In most disease cycles, the basic steps are inoculum production, the spread of inoculum to a susceptible host, penetration of inoculum into a host, infection, secondary cycles, and pathogen survival between host plants.
Why is identification vital?
Identifying pathogens is the first step in controlling plant diseases and producing quality crops. Proper identification is necessary to implement effective management strategies.
COMMON BRAMBLE DISEASES
Cane Blight
The fungus Leptosphaeria coniothyrium causes Cane Blight. Black raspberries are more susceptible to cane blight than other brambles.
Photos courtesy of Department of Plant Pathology, Ohio State University Extension
Symptoms
Cane blight is a weak pathogen that cannot break through the epidermis alone. Cane blight is always associated with a pruning cut, wound, or insect damage. Overwintered canes will show symptoms in early spring, including failure of buds to break, wilting of laterals, or death of floricanes. Symptoms usually occur as the fruit begins to ripen. Dark brown cankers appear around the weak and wilted growth. Canes are weak at the infection site and will often break if bent.
Disease Cycle
The fungus overwinters on dead canes. Old stubs may harbor the disease and produce spores for several years. Insects, water, and wind spread spores.
Spur Blight
The fungus Didymella applanata causes Spur Blight. Purple and red raspberries are more susceptible to damage from spur blight than other brambles. Research shows that blackberries may have immunity against this disease.
Photos courtesy of Department of Plant Pathology, Ohio State University Extension
Symptoms
In late spring or early summer, brown, blue, or purple spots or bands appear on new primocanes and leaf petioles, usually on the lower half of the plant. These lesions enlarge until the cane is girdled. As the disease develops, canes may crack and split lengthwise. Fruiting structures are often visible under the bark. Leaf symptoms appear as brown, V-shaped areas with yellow margins with a wide area at the leaf edge. Damage from winter injury may increase. The yield may reduce due to the withering of infected laterals and eventual death.
Disease Cycle
The disease overwinters in infected canes and will release spores during wet periods from early spring through late summer.
Anthracnose
The fungus Elsinoe veneta causes Anthracnose. Purple and black raspberries are more susceptible to anthracnose than red raspberries. Young growth is most vulnerable to infection.
Photos courtesy of Department of Plant Pathology, Ohio State University Extension
Symptoms
Most often, Anthracnose symptoms are found on canes but can also occur on leaves, petioles, flower buds, and fruit. In the spring, reddish-purple spots appear on young canes. As the disease progresses, the spots enlarge, and the centers become sunken. The typical "gray bark" symptom can be observed in late summer or early fall. Canes infected by anthracnose are more susceptible to winter injury and eventually may die. Cankered canes also might produce abnormal fruiting branches with malformed fruit, especially in seasons of drought. In severe cases, infected fruit is dry and seedy.
Disease Cycle
The fungus overwinters on infected canes from the previous season. Fungal growth found in the gray bark lesions will travel to the plant's crown by rain. New shoots will become infected as they emerge from diseased, old canes. More spores are produced in rainy periods in late spring and wind-carried to other bramble plants.
Phytophthora Root Rot
Phytophthora Root Rot can be caused by several soilborne fungi species belonging to the genus Phytophthora.
Photos courtesy of Department of Plant Pathology, Ohio State University Extension
Symptoms
Once infected, leaves will be prematurely yellow and may appear scorched. Canes will have stunted, weak lateral shoots. As temperatures increase, the fruiting canes wilt and die. The root system of affected canes will have a red-brown color under the epidermis and lack fibrous roots. Often, lesions are visible on infected roots.
Disease Cycle
This disease requires saturated soil conditions for infection. Phytophthora spores travel by swimming through free water or are carried to other plants by splashing water. Once the fungus is present, the pathogen will remain in the soil for several years. Spores may be produced multiple times throughout the season, resulting in the rapid spread of the disease.
Botrytis
The fungal pathogen Botrytis cinerea causes gray mold.
Symptoms
Botrytis is mainly a fruit disease infecting flowers and developing fruit. Open flowers can become infected, especially after frost damage. The flowers become dark and shriveled. Discoloration may range from gray to brown. When moisture is present, fuzzy gray fungal growth can appear on the flowers and the stems. Near ripening, gray mold symptoms typically develop, and the berry will develop a watery rot on drupelets, which will then become covered with fungal growth. Botrytis may also infect foliage and cause cane blight and leaf spotting.
Disease Cycle
Thrives in cool temps between 65 to 75 degrees, wet weather, and when extended moisture occurs right before harvest. This fungus can survive on living and dead plant tissue and overwinters on plant debris and stems. Most infections occur during flowering, and the fungus frequently remains dormant until the berry ripens.
Orange Rust
Orange rust is a fungal disease that impacts black raspberries, blackberries, and occasionally purple raspberries; it is not known to infect red raspberries. Orange rust on blackberries and orange rust on black raspberries are not the same. They are considered two forms caused by two separate but similar fungi. Arthuriomyces peckianus mainly infects black raspberries and has a long cycle. Gymnoconia nitens mainly infects blackberries and has a short cycle.
A. Orange rust symptoms on thornless blackberry. Image courtesy of Erik Draper, OSU Extension, Geauga County.
B. Waxy pustules full of brightly colored orange spores (aeciospores) on leaves of thornless blackberry.
C. Orange rust spores on the underside of a wild black raspberry leaf. Note the powder-like appearance.
Symptoms
Symptoms begin to appear when new shoots start growing. New leaves are deformed, stunted, and have a yellowish or pale green color. Early growth on heavily infected plants is typically weak and spindly. Waxy blisters on the undersides of the leaves will form and turn bright orange and powdery. Infected plants may appear bushy because one bud produces many short, upright shoots.
Disease Cycle
These fungi favor cool, wet conditions, and disease development drastically lowers in temperatures above 80°F. The fungus is systemic and overwinters on canes and roots infected the previous season. The disease is a two-stage infection. Infected plants form the orange pustules of spores. These spores are released in late spring/early summer, infecting older leaves on new plants but staying localized for a few weeks. In late summer/early fall, a second type of spore is produced on the newly infected leaves that will infect buds and growth at the base of new canes. The fruiting bodies that produce these spores are not visible. Newly infected plants generally will not show symptoms that year.
Late Leaf (Yellow) Rust
The fungus Pucciniastrum americanum is believed to be responsible for late leaf rust. Late leaf rust infects red and purple raspberries, not black or blackberries. Some spruce species can act as an alternative host but are not believed necessary for infection. This disease is often confused with Orange Rust, a serious disease infecting blackberries and black raspberries.
Photos courtesy of Department of Plant Pathology, Ohio State University Extension
Symptoms
Late leaf rust can affect leaves, canes, and fruit. As symptoms on fruit do not develop until later in the season, the disease often goes unnoticed on floricanes. Symptoms typically first appear in late July or early August as yellow masses of spores on the underside of leaves; small chlorotic or yellow areas may also be apparent. Unless it’s severe, foliar infections may be difficult to see. Infected leaves may drop prematurely. Infections on berries are often limited to single drupelets, making the fruit unmarketable.
Disease Cycle
This disease requires high humidity for infection. Spores can travel by wind but may also spread to uninfected plantings by machinery or people.
Reminder
Nourse Farms is here to help your plants survive and thrive! Call us at 413-665-2658 or email us at info@noursefarms.com if you have any questions.