The RAIF reports that recent rainfall in the Andalusian community is likely to promote disease development in many crops. Below is a list of the most common diseases affecting Andalusian greenhouses, the ideal conditions for their growth or spread, their symptoms, and recommendations to prevent or minimize their impact on plants.
Botrytis (Botrytis cinerea) is a saprophytic fungus that causes significant damage to many crops, including berries and vegetables. It thrives when days are short, light is limited, and temperatures are around 15-20°C. The fungus requires dead organic matter to initiate infection of live plant tissues. The most common symptom is grey-brown lesions, which can appear on leaves, stems, fruits, flowers, and pruning wounds in some crops. To prevent infection, keep humidity low, ensure good ventilation, prune to improve airflow, avoid high planting densities, and maintain good hygiene by promptly removing infected parts. Limiting nitrogen fertilization can also help, as excessive vigor promotes infection. If necessary, use authorized preventative or curative fungicides, rotating active substances to prevent resistance.
Cucurbit downy mildew (Pseudoperonospora cubensis) affects both protected and outdoor crops, with greenhouses providing ideal conditions for its development. It thrives in mild temperatures (15-25°C) and very high humidity (80-90%), requiring free water on leaves for infection. Temperatures below 5°C or above 35°C inhibit its growth. The spores are easily dispersed by wind, drafts, splashing water, and runoff, especially after heavy rain or sprinkler irrigation. Warm, moist winds carry spores over long distances, allowing the disease to spread from a focal point across large areas through successive contamination. To control it, use resistant or tolerant varieties, ensure ample spacing to improve air circulation, avoid excessive nitrogen, and keep the area clean by removing infected debris. Do not plant susceptible crops together. Regular pruning, especially removing dead or infected leaves, helps reduce inoculum and improve airflow. Adequate air circulation can be achieved by orienting plots with the prevailing wind or installing ventilation systems in greenhouses. If needed, apply approved preventive (contact) or curative (systemic) fungicides, ensuring rotation of active ingredients.
Neck and root rot (Phytophthora spp.) affects a wide range of horticultural crops, including strawberries and citrus, with symptoms varying by host. The disease thrives in high soil moisture and temperatures between 15 and 26°C. The fungus can be transmitted through irrigation water. In seedlings, it causes complete plant death (seedling drop or damping-off), while in mature plants, root and collar rot are common. To manage it, avoid prolonged waterlogging, cultivate on raised beds, and ensure good soil drainage. Adjust irrigation to prevent wetting the trunk, keeping emitters separate from the plant's neck, and maintain short, frequent watering cycles to prevent drought. Thoroughly disinfect machinery, tools, and footwear before moving between plots. Use resistant varieties and rootstocks when possible. Remove and destroy diseased plant debris, including leaves and roots, to prevent spread. Keep organic matter away from the trunk base, avoid wounding the trunk or roots during handling, and apply authorized fungicides, such as cupric compounds or Fosetyl-Al, particularly after rain. Soil disinfection by solarization or biofumigation can be performed during sowing or transplanting.
Source: juntadeandalucia.es
