Managing Microbial Plant Diseases: Expert Answers to Common Questions

The Top Five Questions Growers Have About Bacterial and Fungal Plant Diseases

Unmanaged bacterial and fungal diseases can lead to unhealthy crops, severe crop loss, or unmarketable yield. It is important to understand proper management techniques to limit disease incidence and severity in your field, maximizing crop production and potential.

In this blog article, we address the top five questions most growers have about how microbial-based crop diseases occur and review options for reducing disease incidence in current and future cropping seasons.

Question #2: Will my crops have the same disease next year?

Many disease-causing pathogens remain alive in the soil and plant tissue left behind from the previous growing season until conditions are favorable to infect new plants. This phenomenon is called overwintering. If you ended the season with high disease pressure, it is likely that there will be disease pressure in the following season, and you need to develop a treatment program to limit disease and preserve crop health.

Question #3: What common pathogens overwinter?

Several species of plant pathogens overwinter in association with infected plant tissue. Some examples of common pathogens that can survive and infect new crops include bacterial pathogens, which lead to diseases such as:

• blight (Xanthomonas campestris),
• soft rot (Erwinia carotovora and others),
• bacterial spot (Pseudomonas syringae),
• crown gall (Rhizobium radiobacter previously Agrobacterium tumefaciens),
• and many others.

Fungal pathogens also overwinter in infected tissue and include diseases such as

• rusts (Pucciniales spp.),
• smuts (Ustilago esculenta),
• downy mildew (Peronospora manscurica),
• powdery mildew (Erysiphe, Microsphaera, Phyllactinia, Podosphaera, Sphaerotheca, and Uncinula),
• brown rot (Phytophthora spp.),
• soft rot (Phythium spp. and Fusarium spp.),
• fusarium wilt (Fusarium spp.),
• verticillium wilts (Verticillium spp.),
• molds,
• and cankers among others.

It is important to remember that some diseases can be caused by a variety of pathogens, and the disease name is simply a description of the visible symptoms produced by the infection. Due to the extensive variety of pathogens that can overwinter, it is wise to be proactive in treatment and prevention practices against a broad spectrum of bacterial and fungal pathogens.

Question #4: What can I do to prevent future diseases if so many pathogens overwinter?

1. Consider crop rotation. Many pathogens are host-specific and will only infect certain varieties of crops. Crop rotation may not be possible in specific growing operations, so consider the following points.
2. Choose resistant varieties when possible. Some crops have been bred for improved resistance against specific pathogens.
3. Completely remove all infected plant material at the end of the season. If possible, remove infected material throughout the season and pull plants with major infections to prevent further outbreak and overwintering in the soil.
4. Spray or treat fields with effective products throughout the season to prevent major infections and limit the overwintering population.

Question #5: What are some effective products that I can use to treat my crops?

Kemin has a full portfolio, including pesticides that aid in pest and pathogen reduction. Proper use throughout the growing season should help to limit overwintering pathogen populations. The two Kemin products listed below should specifically improve crop health.

The use of PathoCURB through the growing season should reduce microbial disease incidence and an application prior to crop removal, which will limit overwintering populations. Providing your crops with our Valena fertilizer will jump-start healthy plant growth. Healthy plants are generally less susceptible to disease than plants that are not provided with proper nutrients^2,3.  

References:

1. Francl, L.J.  2001. The Disease Triangle: A plant pathological paradigm revisited.
The Plant Health Instructor. DOI: 10.1094/PHI-T-2001-0517-01

2. Tripathi R, Tewari R, Singh KP, Keswani C, Minkina T, Srivastava AK, De Corato U, Sansinenea E. Plant mineral nutrition and disease resistance: A significant linkage for sustainable crop protection. Front Plant Sci. 2022 Oct 20;13:883970. doi: 10.3389/fpls.2022.883970. PMID: 36340341; PMCID: PMC9631425.

3. Allen J. Plant diseases & sustainably healthy plants. University of Connecticut, College of Agriculture, Health and Natural Resources, Extension News. 2014 Jul2. https://news.extension.uconn.edu/2014/07/02/plant-diseases-sustainably-healthy-plants/#:~:text=Healthy%2C%20vigorously%20growing%20plants%20are,leaves%20to%20keep%20them%20dry.

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