November 8, 2023
Rose cultivation poses unique challenges, with Downy Mildew and Botrytis diseases standing out as prominent adversaries. Growers are well aware that the occurrence of these diseases can be correlated with the prevailing weather conditions and the microclimate within the greenhouse. The interplay between these diseases and the climate is a multifaceted relationship significantly influenced by the rose varieties being cultivated. This intricate dynamic can be aptly illustrated by the concept of the disease triangle.
The disease triangle succinctly encapsulates the critical components of disease occurrence: the presence of a susceptible host, a conducive environment, and the existence of the pathogen. When these three elements converge, it creates an environment conducive to disease development. Consequently, the adoption of holistic disease management strategies becomes imperative, with a primary goal of mitigating these factors and creating conditions that are inhospitable to the onset of a disease outbreak within the crop. As growers prepare for the impending rainy season, strategies to combat Downy Mildew and Botrytis should be at the forefront of their priorities.
Key Insights into Downy Mildew
Downy Mildew, scientifically known as Pseudoperonospora sparsa, is readily identifiable through the emergence of violet and brown patches on the rose leaves. These affected leaves eventually yellow and fall from the plant. Upon closer inspection, a greyish mold is often observed on the undersides of these leaves. This insidious disease thrives under conditions characterized by high humidity and low temperatures, making it particularly prevalent in unheated crops, such as those cultivated in plastic tunnels and greenhouses, where nighttime temperatures can sharply decline.
Key Insights into Botrytis
Botrytis, colloquially referred to as ‘grey mold,’ derives its name from the characteristic appearance of grey powder that forms on the leaves, flowers, fruit, or stems of infected roses. This destructive fungus penetrates plant cells through a pollen tube, leading to their demise, and subsequently consumes the contents of these deceased cells. The result is the formation of grey-brown spots on leaves, stems, fruits, and flowers, which progressively enlarge, culminating in the development of the distinctive “weft.”
Koppert’s innovative product, “NoPath,” harnesses the power of essential oils and is instrumental in the prophylactic management of Downy Mildew through the induction of ISR (Induced Systemic Resistance). To trigger ISR, NoPath is administered to the crop through root zone drenching. The Koppert team underscores the profound benefits, stating, “Overall, when crops are treated prophylactically with NoPath, growers experience reduced disease pressure, thereby diminishing the need for corrective chemical fungicide applications.”
These proactive strategies represent a significant leap forward in the efforts of rose growers to protect their crops from the detrimental impacts of Downy Mildew and Botrytis. As the rainy season approaches, these comprehensive approaches are poised to be instrumental in fortifying the resilience of rose cultivation.