As the harvest season ends, many growers face an invisible, silent, but significant threat: the survival of diseases in the crop during wintertime. These diseases, for example Fusarium spp, can lurk in the soil or plant debris, ready to strike when conditions are favourable at the start of the new season. Understanding how these pathogens survive the winter, the types of diseases involved, and the impacts on future crop cycles is crucial for effective management and prevention.
Overwinter on debris: How does it work?
Diseases often reside on plant debris left in the field after harvest. This debris can include fallen leaves, stems, and other organic material that has not been properly disposed of or managed. Pathogens such as fungi, bacteria, and viruses can survive the harsh winter months in this material.
Many diseases produce resistant spores or structures, like sclerotia or oospores, which can withstand freezing temperatures and remain viable for extended periods. These structures can germinate and infect new plants when the weather warms up, leading to outbreaks in the next growing season. The cycle continues unless the debris is effectively managed.
Types of Diseases
Several common diseases are known to overwinter on debris, including:
-
Fungal diseases: Examples include Fusarium, Phytophthora, and Botrytis. These fungi can cause root rot, blight, and other issues that affect plant health.
-
Bacterial diseases: Bacteria like Erwinia and Pseudomonas can survive on decaying plant matter and lead to issues such as soft rot and bacterial wilt.
-
Viral diseases: Certain viruses can persist in debris or infected plant tissues, ready to infect new crops once conditions become favourable.
Understanding the specific pathogens that can overwinter in your region is vital for tailoring management strategies.
Impact on the next crop cycle
The presence of overwintering diseases can severely impact the next crop cycle and infected debris can lead to:
-
Reduced crop yields: Crops may suffer from stunted growth, lower quality, or complete dying-off of the plant if they become infected early in the season.
-
Increased pest pressure: Some diseases can attract pests, creating a compounded problem as insects carry the pathogens to healthy plants.
-
Economic losses: Growers may face higher costs related to treatment and lower market prices due to decreased crop quality and yield.
Early detection and management of these diseases are crucial to mitigate their impact on future harvests.
Importance of early control
Implementing early control measures is essential for managing overwintering diseases. By prioritizing early intervention, growers can significantly decrease the chances of disease outbreaks in the following season. Some of these practices include crop rotation, proper sanitation, soil management, and the use of biological control agents that are effective at targeting diseases in colder temperatures. The early application of biocontrol agents is crucial to build a robust IPM program. Most biocontrol agents work best when applied preventively at the start of the season.
One of these agents is Koppert’s seed treatment Cerall (Pseudomonas chlororaphis strain MA342) which is a liquid formulation that is ready to use and can be applied directly with regular liquid seed treatment equipment. This bio-fungicide is a biological seed treatment to control seed-borne fungal diseases in cereals, including winter wheat, summer wheat, spelt, rye, and triticale. It supports the growth and development of young cereal plants up to the five-leaf stage and is suitable for organic and conventional cultivation. With an increasingly narrow range of products, Cerall is the future-proof solution against seed-borne diseases such as Fusarium spp., Tilletia caries (common wheat bunt, stinking smut), Microdochium nivale (foot rot, head blight) and Parastagonospora (a.k.a. Septoria) nodorum (glume blotch, or leaf spot disease).
Two other great examples of biocontrol agents key to early control are Trianum and V10. Trianum, Trichoderma harzianum T22, colonizes the root system of plants and thus protects numerous crops against soil pathogens such as Fusarium, Pythium, and Rhizoctonia. Experience in the field has shown that Trianum-P reduces the fungal inoculum of Stemphylium in pear during the pear vegetative growth by at least 50% and reduces the fungal overwintering inoculum with 80% to 90%. V10 is a natural crop protection agent with the active ingredient Pepino mosaic virus (VX1 and VC1). V10 is used preventatively and applied to young plants to prevent the emergence of the virulent Pepino mosaic virus (PepMV) in tomatoes. Growers have reported up to 85% protection of greenhouse tomatoes using V10.
Role of weather and impact of milder winters
Weather plays a critical role in the survival and spread of overwintering diseases. Milder winters, which are becoming more common due to climate change, can exacerbate the problem. Warmer temperatures may allow pathogens to survive and remain active for longer periods, leading to earlier and more severe outbreaks in the spring. In addition, changes in precipitation patterns can influence soil moisture levels, impacting the viability of certain pathogens. Increased humidity and wet conditions can create a conducive environment for fungal spores to germinate and spread.
Diseases pose a significant threat to crop health and agricultural productivity. By understanding where and how these diseases survive, the types of pathogens involved, their impact on future crops, and the importance of early control measures, growers can take proactive steps to protect their plants. Biological control agents are an important building block for an Integrated Pest Management (IPM) program. Additionally, recognizing the influence of weather patterns, particularly milder winters, can help in adapting management strategies to ensure resilience in the face of changing environmental conditions.