The Role of Naturally Occurring Defense Mechanisms in Disease Resistance

After years of research, there is greater understanding of the detection mechanism which gives plants the ability to detect when they are under attack by various micro-organisms.  It is now understood that pathogenically invading organisms generate various signal molecules as a result of their infection. These signals can be detected by the plant, leading to the production of immune responses similar to those generated by a flu shot in the human body.

Although a wide range of events can stimulate the production of the plant’s immune system, once stimulated, it follows a fairly uniform path to help the plant protect itself.  Therefore, an infection by a viral, bacterial, fungal or other disease-causing agent may elicit the same defense response.  The response is then distributed throughout the plant to help the whole plant acquire the “immunity” or some form of protection or resistance against a wide spectrum of pathogens or diseases.  Because of this observation, such self protection has been labeled Systemic Acquired Resistance, or SAR, and it is present in a wide range of different plant species.  Among other responses, SAR involves the production of the well-known plant product salicylic acid, which is closely related to the famous human pain reliever Aspirin, or methyl-salicylic acid.

With this information, agricultural companies have been able to develop a range of foliar applied products that also stimulate the SAR system in plants.  These products are typically used prophylactically to protect plants against impending or early stages of disease outbreaks.  Such protection can be significant, and in many cases, it appears to last for some time after it has been triggered.  Two products that actively stimulate a plant’s SAR mechanisms and help prevent disease infection are Kendal® and Vacciplant®.  Both contain naturally occurring small carbohydrates closely related to those produced when a disease infects a plant.  When sprayed on a crop, the plants react as if they are under disease attack and trigger their own defenses, helping provide protection to diseases such as Phytophthora, Pythium, Fusarium, Verticillium, various mildews and other infections.

Disease tolerance can also be enhanced with products containing phosphite such as the fungicide ProPhyt® and the nutritional Ele-Max® Phosphite MAX.  By providing phosphite and other foliar nutrients, these types of products improve plant health for an enhanced ability to resist infection.  They can be used alone in anticipation of a disease outbreak, and they can significantly enhance the effectiveness of other fungicides when used in tank mix combinations. Contact your Helena representative for more recommendations to help activate your crop’s defenses.

- Ian Watkinson Ph.D., Product Manager, Southern Deserts Region