7/2/2013 - By Matthew Shultz

This month I want to focus on a fungal disease that can infect a wide range of host plants: Botrysphaeria. Botrysphaeria is not host specific and attacks many plant types. This pathogen is very opportunistic and will usually only attack stressed or weak host plants. Plants that are environmentally stressed from drought, temperature stresses, or excessive irrigation are most susceptible.

The disease first appears on a few branches of infected plants in mid spring, these infection sites usually cause the leaves to wilt and can often be mistaken for lack of irrigation. Some growers water these plants even heavier which only helps to compound the problem, and never really helps the plants as lack of water isn’t the problem.

This initial infection is caused by spore fruiting bodies that overwinter on plant debris. As the disease progresses the wilting symptoms will usually subside, but this now means that the pathogen has moved into the vascular system of the plant and will soon begin infecting the entire host plant. Plants infected to this degree should have dead wood and branches trimmed out to help prevent further spread.

Often a canker will form at the infection site that looks like a black to gray water soaked spot on the branch or trunk. Make trimming cuts 6-12 inches below this canker. Another good diagnostic indicator for this disease is to peel back the bark from the infected plant material. The tender wood underneath will show signs of reddish to orange to brown streaking which helps when identifying this pathogen. Always have pathology tests done before applying fungicides.

Control of Botrysphaeria is easily achievable with a solid spray program, as this pathogen is opportunistic. Rotations including Pageant, Protect DF, and tebuconazole are very effective when used in a preventative manner. However like most fungal diseases, once the symptoms have appeared the disease is usually there to stay for at least the growing season, so prevention is key!

Plants that are already showing severe canker formation and oozing should be removed and disposed of. For more information on controlling this disease or any other pests that might be causing you headaches please contact your Harrells technical service rep!