By The Certis Team
Fire blight can be extremely destructive to apple and pear orchards if left unchecked, and it is a disease that is multi-faceted and difficult to fully control. Growers should be aware that fire blight spreads easily, and there is not a clear-cut treatment for complete control, so you must put preventive measures in place to stop the disease before it takes over your orchards.
Integrated pest management (IPM) can be implemented in apple and pear orchards to curtail the onset and spread of fire blight through methods such as proper sanitation, tree care practices, and biological products to help prevent and control the spread of disease.
Let’s uncover IPM best practices to diminish fire blight in orchards.
1. Prep Your Orchards
The first step to managing fire blight is largely preventive: the selection of your cultivars. Some cultivars are moderately resistant, so if possible, choose varieties of this type, and you can already improve your chances of having disease-free trees. However, cultivar choices are limited and may be more susceptible to the disease due to existing cultural traits in some pear and apple varieties.
Whether or not you have resistant cultivars in your orchards, it’s still important to take other preventive measures throughout the off season and during the growth of trees and blossom.
Sanitation is imperative to decrease the spread of fire blight disease in susceptible trees. Frequently check trees for overwintering or “holdover” cankers along with blighted twigs and prune as necessary to remove inoculum during the winter before the growing season. If cankers are not removed during the dormant winter season, the bacteria will become active and ready to spread and create new infections in the spring.
Remember: even if you have no history of cankers in your orchards, look for them and remove with sanitary care – fire blight can easily sneak in and spread rapidly.
2. Carefully Inspect and Prune
When it’s time for growing season, keep a keen eye out for signs and symptoms of the fire blight disease cycle, like shoot infections, water-soaked twigs and blossoms, discoloration, and eventually bacterial ooze.While pruning in winter is important to prevent the onset of spring diseases, it is also critical as trees grow, as fire blight can spread rapidly once activated in an infected tree.
To remove blighted parts of trees:
- For twigs, cut into dry, healthy tissue 4 inches or more below visibly dead wood.
- For cankers, remove dead tissue of trunks or large branches until you see only healthy tissue.
- Take any infected plant tissue completely out of the orchard to burn or place into the trash so that it does not re-infect any nearby trees.
During spring and summer, disease can spread even more rapidly, so practice proper sanitation practices so that fire blight does not infect healthy tissue. If you must cut to remove diseased parts of trees, cut dry wood 12-15 inches below the diseased portion and sanitize tools between each cut in a 10% bleach solution combined with a few drops of liquid dish soap.
3. Apply Effective Biological Products
If you’re an organic or conventional grower, IPM programs can greatly increase the health of your trees and help prevent the onset and spread of fire blight in apple and pear orchards.
Keep in mind that fire blight follows a very specific disease cycle with multiple factors that can increase the severity of the disease, so you should follow prevention methods all year.
During Winter:
- Follow sanitary canker removal practices and apply a dry copper fungicide to treat during dormant periods.
Before Bloom:
- Select products that are natural predators to fight bacteria and fungi to maintain healthy trees.
- Choose a biological plant activator and spray before bloom at tight cluster when the tissue is green. This will activate the defense mechanisms in the tree to fight bacteria as they grow. Alternatively, you can apply a blossom protectant, but activators actually resist infection and development of disease rather than adding a protective cover that could be permeated.
- Apply bactericides with varying modes of action to fight diseases from multiple angles. For example, a copper fungicide can coat and protect the plant tissue and disrupt bacteria on the plant surface, while multi-action liquid bactericides break up the bacteria structure so that it can’t multiply and spread.
Throughout Fruit Growth:
- Continue applying insecticides and fungicides as needed and according to label instructions to prevent and control any fire blight outbreaks. Spring to harvest is the best time for liquid coppers.
- To help break or disrupt the disease cycle, choose a targeted bactericide that specifically attacks Erwinia amylovora on apples and pears to destroy bacteria cells so that they cannot spread and infect.
Of course, there are events you can’t prevent or plan for, like environmental trauma such as hailstorms or other severe weather. If (and when) trauma blight occurs in your orchard, you can be ready to treat immediately with a gentle copper fungicide to sustain trees after exposure to Erwinia amylovora, the bacterium that causes fire blight.
Biological products are a great choice for IPM programs because they help to manage chemical resistance, are non-harmful to beneficial organisms and the environment, and can typically be great tank-mix partners with other products.
If you’re looking for a broad portfolio of solutions to control the bacteria that causes fire blight in both organic and conventional orchards ideal for IPM programs, we can help you fight the blight.
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