Arkansas Fruit, Vegetable and Nut Update

Managing Diseases in Blackberry – Building a Fungicide Spray Schedule

by Aaron Cato - March 28, 2023

Blackberry is often thought of as a resilient plant that will grow and produce fruit anywhere. Sometimes that distinction leads to the thought that blackberries require very few inputs to grow. What we know is that blackberry can be challenging to grow commercially, and you need to protect plants to assure that you will have good quality fruit to sell in the summer. Disease management is an important aspect of blackberry production, and one that growers need to focus on each year.

Without good disease management, growers should expect lower overall yields, decreased fruit quality and a heightened risk of losing plants. Proper management of blackberry diseases require a concerted effort towards cultural control tactics as well as a fungicide spray program. Outlined below is a framework for disease management that you can use in your blackberry operations. All of this information is also explained at length on our recently posted YouTube video here:

Cultural Control Tactics

Maximizing cultural control tactics will be key in preventing serious disease issues. The following cultural control tactics should be employed every year:

Manage weeds to help increase airflow between rows of blackberries and at the base of plants.
Clean up field edges and hedgerows to maximize airflow into plantings and remove all nearby wild blackberries where possible.
Avoid excess nitrogen to minimize excessive foliage and maximize airflow through canes.
Remove all harvested floricanes (second-year canes) immediately after harvest is finished and burn them outside of the planting. This will lower disease inoculum within plantings significantly.
Remove all damaged or galled canes. Prioritize keeping healthy canes when pruning, as damaged or galled canes will have reduced yield and will increase risk of damage from insects and disease.

Preventative Fungicide Spray Program

In addition to these cultural practices, a preventative fungicide spray program is necessary to lower the amount of disease inoculum present and protect susceptible fruit and canes from infection by pathogens. This spray program should begin with a lime sulfur/Sulforix™ application at the delayed dormant timing and continue until just before blackberries go dormant in the Fall. Selection of fungicides to spray every 10-14 days should be made based on the following factors:

What growth stage are you currently at? Knowing the growth stage tells you which disease you should be trying to prevent and which fungicide mode of action (MOA) you should utilize.
What diseases do you typically deal with? Field history tells a lot about how you should fashion your spray schedule. This is especially important if you currently have anthracnose issues.
Which fungicide did you last spray? It is incredibly important to rotate effective MOA to prevent resistance issues and maximize fungicide efficacy.
Is harvest occurring? Be sure to read fungicide labels and be aware of their preharvest intervals.
Be aware of the maximum use rate for all products you plan to spray. This information is provided on the fungicide label, but I also have provided it in Figure 1 for many products.

Example spray program for commercial blackberry production in Arkansas.

Figure 1. Example spray program for commercial blackberry production in Arkansas. Watch the following YouTube video for more information on how this schedule was built to prevent each disease: https://youtu.be/cDVmcC2aZ7E