Fungal diseases can take many forms. Some symptoms are subtle and barely noticeable, while other symptoms may stand out like a bright beacon. The latter is true of orange rust of blackberries. Continue reading to learn more about the symptoms of blackberries with orange rust, as well as blackberry orange rust treatment options.
About Blackberries with Orange Rust
Blackberry orange rust is a systemic fungal disease that can be caused by two fungal pathogens, Arthuriomyces peckianus and Gymnoconia nitens. These pathogens can be distinguished by their spore shape and life cycle; however, they both infect blackberry plants the same way and cause the same symptoms and damage.
As a systemic disease, once a plant is infected, the infection is present throughout the entire plant for the rest of the plant’s life. Even when symptoms may appear to go away, the plant is still infected and can still spread the disease. The disease is most commonly spread by released spores that are carried on wind or water, but can also be spread in the grafting process or by dirty tools.
Initial symptoms of orange rust of blackberries are yellow or discolored new growth; spindly, wilted or sickly appearance of whole plant; and stunted, twisted or deformed foliage and canes. Waxy blisters may form on the margins and underside of foliage. These blisters eventually turn a bright, shiny orange color as the disease progresses.
The orange pustules then release thousands of fungal spores which can infect other blackberry plants. Infected leaves may wilt and drop, spreading the disease in to the soil below. Orange rust of blackberries is most infectious when temperatures are cool, wet, with high humidity.
Blackberry Orange Rust Treatment
While orange rust infects blackberries and purple raspberries, it does not infect red raspberry plants. It also rarely results in the death of infected plants; however, it does severely inhibit the fruit production of infected plants. Plants may produce some fruit at first, but eventually they stop producing all flowers and fruit. Because of this, orange rust is considered the most severe fungal disease of black and purple brambles.
Once a plant is infected with orange rust, there is no cure but to dig up and destroy infected plants. It is recommended that no black or purple brambles be planted in the same site for at least four years.
Preventative fungal sprays can be used on new plants and the soil around them. Proper sanitation of tools and garden beds can also help in controlling blackberry orange rust. While blackberry orange rust treatments are limited, certain varieties have shown resistance to the disease. For resistant varieties try:
- Ebony King