Potential Impact Of Regalia® Treatments On Tree Health And Vigor

Regalia®, an extract from giant knotweed (Reynoutria sachalinensis (REYSA)), is an organic immune system response (ISR) treatment that can mitigate fungal and bacterial infections by stimulating the genetic immune response system of a plant. The mode-of-action of Regalia® is to penetrate the plant tissue and stimulate a biodynamic response to resist pathogens. The primary response to Regalia® is the production of reactive oxygen species (ROS) that disable pathogens, and a thickening of cell walls to inhibit pathogen penetration. Regalia® is an uncommon fungicide since the protection is provided by the plant itself and not directly by the agent, and because the activity is internal rather than external. This process provides protection from pathogens that get past surface protectants. Because ISR agents require plant resources to be effective, there is a risk that they can disrupt the metabolic processes of the plant, or there can be an allocation cost that could diminish the plant vigor. This study examines if the ISR activity of Regalia® presents any phytoxicity or impact to vigor in four varieties of cider apples (Malus ×domestica cvs. Dabinett, Medaille d’Or, Chisel Jersey, and Redfield). This quantitative study, based on measured metrics of plant growth during the study period, showed that Regalia, applied with Cueva or Serenade, had no effect on primary or secondary shoot length or the number of shoot leaves on any of the four test varieties.