Swede crops, known for their hardiness once established, are not immune to fungal diseases. After I have got over the hurdle of getting the swede crop germinated and past the rough leaf stage I then need to watch for fungal diseases in the crop.
I find it easier to address problems if I know what to look out for, so I have compiled a list of some of the most common fungal diseases in UK swede crops, I have also provided the name of a chemical treatment, and when it should be applied.
Chemicals are constantly being withdrawn from use, so if you need one which is not available in your area, perhaps you can find another.
Clubroot (Plasmodiophora brassicae)
Description: Clubroot causes swelling and distortion of roots, leading to stunted growth. It thrives in acidic, moist soils.
Treatment: Adjust soil pH to 7.0 or above with lime. While no specific fungicides are recommended, soil fumigants and biological controls may be utilised.
Timing: Soil pH adjustment should occur before planting.
Powdery Mildew (Erysiphe cruciferarum)
Description: Manifests as white, powdery spots on leaves, reducing photosynthesis and potentially stunting growth.
Treatment: Use sulfur-based fungicides or systemic options like myclobutanil.
Timing: Apply at the first sign of infection, following label intervals.
Downy Mildew (Hyaloperonospora brassicae)
Description: Features yellow patches on upper leaf surfaces and fluffy, white to grey mould underneath.
Treatment: Metalaxyl or mefenoxam-based fungicides are effective.
Timing: Apply preventatively or at the first disease sign, following label directions.
White Leaf Spot (Pseudocercosporella capsellae)
Description: Causes small, circular, white spots on leaves, leading to tissue death in severe cases.
Treatment: Chlorothalonil or mancozeb can manage this disease.
Timing: Apply during cool, wet weather when disease development is likely.
Ring Spot (Mycosphaerella brassicicola)
Description: Grey or pale spots with dark borders appear on leaves, defoliating plants in severe infections.
Treatment: Fungicides like azoxystrobin or pyraclostrobin are recommended.
Timing: First signs of disease usually trigger application, especially under wet conditions.
Light Leaf Spot (Pyrenopeziza brassicae)
Description: Small, pale spots with darker borders weaken the plant.
Treatment: Prothioconazole or tebuconazole are effective treatments.
Timing: Target early disease phases from autumn to spring.
Blackleg (Leptosphaeria maculans)
Description: Dark lesions on stems lead to lodging and stem breakage, particularly harmful to young plants.
Treatment: Use fluxapyroxad or pyraclostrobin, and treat seeds with fungicide before planting.
Timing: Apply fungicide to seeds before planting and to foliage at the first disease sign on seedlings or young plants.
I have provided a brief overview of the key fungal threats to swede crops in the UK and how to combat them effectively. Remember, fungicide application should be part of an integrated pest management strategy, including using resistant varieties and good crop rotations, to ensure the health and productivity of your swede crops. I will add specific images as they appear.
