Hydroponic cucumbers. Photos by Anna Testen.

Oct 26, 2024
Refreshing your disease management plan

Whether you have struggled with diseases in the past or diseases are the bane of your crops, now is a good time to develop or revisit plans for managing diseases in your operation. Planning for diseases will help to make effective management decisions, prioritize resources and help reduce and even prevent disease losses. 

When developing or refreshing your operation’s disease management protocols, it is important to correctly identify and prioritize diseases and maintain good records to help with future oversight and strategy. 

Know thy enemy

Disease management hinges on accurate diagnosis of the pathogens plaguing your crops. Misdiagnosis leads to the selection of ineffective management strategies. An example is misdiagnosing a viral or bacterial disease as a fungal disease and spraying a fungicide, wasting time and resources as the fungicide will have no impact on those pathogens. 

Diagnostic resources are available online from university Extension websites and in print, including disease compendia for individual crops. Additionally, local plant disease diagnostic clinics, Extension educators or plant pathologists can help with malady diagnosis. 

Regular scouting is needed to ensure that any condition is identified in a timely manner. However, infections caused by viruses or soilborne pathogens can be somewhat hidden in nature as they can be difficult to observe. 

Symptoms of some viral diseases can be subtle and confused for nutrient deficiencies. If you suspect a viral disease, contact your local plant disease diagnostic clinic for testing options. 

ASD high tunnel. Photos by Anna Testen.
ASD high tunnel. Photos by Anna Testen.

Soilborne diseases can also cause symptoms similar to nutrient deficiencies, such as stunting and yellowing. Check roots and stems during the growing season and at season’s end for disease symptoms.

When directing management efforts towards specific disease priorities, growers can save time and resources. Strategies for aggressive, fast-acting pathogens need to be in place to prevent and reduce losses.

Phytophthora blight in cucumbers. Photo by Anna Testen.
Phytophthora blight in cucumbers. Photo by Anna Testen.

Examples of aggressive pathogens are Phytophthora infestans, which causes late blight in potatoes and tomatoes, and Phytophthora capsici, which causes blight of cucurbits and pepper. Diseases that directly affect the consumers’ end product, such as green bean anthracnose, should be prioritized. 

Some diseases can be annoying but do not affect yield or produce quality in a meaningful way. Other infections may occur rarely in your area due to climate or regional disease differences, making that condition a low priority in terms of management resources. Ideally, growers should still implement a mitigation plan for lower priority diseases that don’t affect your bottom line in a meaningful way.

Mix it up 

Decisions that impact diseases occur at every step of crop production — from variety selection to final harvest and storage. There are many disease management tactics available to growers, and the most important thing to remember is to combine multiple tactics when building a disease management “toolbox” for your operation. 

Sclerotinia in cabbage. Photo by Anna Testen.
Sclerotinia in cabbage. Photo by Anna Testen.

When considering resources to use, it helps to consider the integrated pest management (IPM) pyramid (Fig. 1). Prevention should be an even more important part of your production, more so than disease management. These strategies include selecting resistant varieties when available, sanitation and use of clean seeds, propagules or transplants. 

Cultural tactics that reduce pathogen establishment or eliminate existing populations should then be considered. These methods include appropriate site selection, environmental management, vector management, crop rotation and balanced fertility and irrigation. 

Fusarium wilt on tomatoes. Photo by Anna Testen.
Fusarium wilt on tomatoes. Photo by Anna Testen.

Physical and mechanical methods of disease management include use of protected culture, mulching, tillage, solarization and soil steaming. Use of biologicals is growing, and biological options are likely available to help with priority diseases in your operation. With biologicals, it is important to get ahead of the pathogen, so apply biologicals early and often. Success is often dependent on the environment and the level of disease already present, so results may be variable. Synthetic pesticides play an important role in disease management but should not be relied on as the sole tactic. 

Late blight on tomato. Photo by Anna Testen.
Late blight on tomato. Photo by Anna Testen.

Remember to stack the different tactics you use to ensure better disease management. Talk with growers, Extension educators and university and government researchers to find out about new disease management options for your crops. 

Some newer resources management, including anaerobic soil disinfestation, have shown to be effective in vegetable production. Trialing a new management tactic in a portion of your crop can provide valuable insights to new management options.

Document your past successes and failures

It is important to keep track of disease management tactics used in your operation and whether they are effective. Diseases never occur singly, so it can sometimes be hard to keep track of how successful management tactics have been for a specific disease. 

Photo by Anna Testen.
Photo by Anna Testen

Pesticide applications are easy to record, and the impacts are usually easy to see. It can be difficult to document the impacts of broader disease management strategies, such as crop rotations, variety selection and sanitation. However, keeping good records of disease management practices along with annual observations will help identify practices that are reducing infections.

Whether you are a new or experienced grower, it is important to refresh your disease management plans to stay on top of your existing disease issues and be prepared for new and emerging diseases.

Written by Anna Testen

Anna Testen
Anna Testen

Testen is a research plant pathologist with USDA-ARS in Wooster, Ohio, focused on developing disease management strategies for controlled environment agriculture specialty crops. She has worked on vegetable, fruit and ornamental disease management projects in the U.S., Ecuador, Bolivia, Tanzania and Ethiopia. For questions, please email the author at [email protected].

 

 




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