Boysenberries are a fiber and vitamin C rich, vining hybrid mixture of raspberries, blackberries, and loganberries. Hardy in zones 5-9, boysenberries are eaten fresh or made into preserves. When growing boysenberries, well-draining, sandy soil and proper watering are essential to prevent many common fungal diseases. In fact, boysenberry plants are so susceptible to a number of fungal conditions that many gardeners have become reluctant to even try growing them. In this article, we will take a closer look at common boysenberry pests and diseases.
About Boysenberry Problems
Once a popular garden plant, boysenberries are seldom grown in home gardens today because of their susceptibility to fungal diseases and certain insect pests. However, fungal diseases can happen to any plant.
Fungal problems with boysenberries can be prevented with proper sanitation and irrigation practices. Providing plants with adequate air circulation is one such practice. Giving plants a little extra space of their own and pruning out crowded old canes can increase air circulation for plants. It is also important to clean up garden debris and weeds, which may harbor fungal spores around boysenberry plants.
Proper irrigation practices basically means always watering plants directly at their root zone, rather than overhead watering. Overhead watering can cause wet spots on foliage which fungal spores can easily adhere to. Overhead watering also creates more opportunities for soil borne pathogens to splash back up onto plant tissues. A light, gentle trickle directly at the root zone is always best.
It is also recommended that you not plant boysenberries in a site which housed tomatoes, eggplants, or potatoes in the last 3-5 years, as these plants may have left harmful disease pathogens in the soil.
Common Boysenberry Pests and Diseases
Below are some common boysenberry issues:
Anthracnose – Also called cane dieback, anthracnose is caused by the fungal pathogen Elsinoe veneta. Symptoms may first be noticed in spring to early summer as small purple spots on new shoots or spots with purple margins. Spots will grow larger, take on a more oval shape, and turn gray as the disease progresses. Eventually, infected canes will die back. Using fungal dormant sprays can help prevent this disease.
Cane and Leaf Rust – Caused by the fungus Kuehneola uredinis, cane and leaf rust symptoms will first appear as small, yellow pustules on the canes and foliage of boysenberry plants and their relatives. As the disease progresses, foliage will become heavily spotted and the canes will crack and dry out. Foliage may also dry out and become brittle. Cane and leaf rust is not a systemic disease, so it only affects the canes and foliage not blooms or fruit. Infected canes and foliage should be pruned out and destroyed.
Crown Gall – Caused by an agrobacterium, crown gall is a bacterial disease common in boysenberry plants. Symptoms are large, wart-like galls on the roots and base of canes. If these appear, infected plants should be dug up and destroyed immediately.
Dryberry Disease – There are actually two diseases commonly known as dryberry disease in boysenberries. The first is common downy mildew, caused by the fungus Peronospera sparsa. The second is also a fungal disease caused by the pathogen Rhizoctonia rubi. Both diseases cause berries to suddenly shrivel up and dry out. Unripened berries will become dry and crumble. Canes may also display necrotic spots. Infected plants should be dug up and destroyed.
Orange Rust – Orange rust can be caused by two separate fungal pathogens Gymnoconia peckiana or Kunkelia nitens. At first, small yellow spots may appear on both sides of boysenberry foliage. The spots on the undersides of the foliage will grow to form irregularly shaped pustules. When conditions are right, these pustules will burst open releasing orange spores. Orange rust is a systemic disease that does infect the entire plant, though symptoms only appear on the foliage. Infected plants will not produce harvestable fruit. Plants with orange rust should be dug up and destroyed.
Septoria Cane and Leaf Spot – Caused by the fungus Mycosphaerella rubi, septoria cane and leaf spot is very similar to anthracnose of boysenberry. Symptoms are spots with light brown to tan centers. Tiny black spots may also appear in the larger brown to tan spots. Copper fungicides may help control this disease.
Some common insect problems with boysenberries are: