Disease Identification and Control


Ring Spot

Technical Name: Mycosphaerella Brassicicola General: Dormant over winter. Found mostly in spring crops. In spring spores are produced infecting leaves and seed pods. Can cause substantial crop yield loss. Identification: It produces characteristic dark rings/ spots Lesion margins are yellow. Crop symptoms include and leaf yellowing. Leaf drop can occur as infection progresses. Can be […]

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Leaf Spot

Technical Name: Alternaria Spp. General: Spreads via wind-borne spores produced by lesions on crop residue or weeds. Wet humid weather favours spore production. Infected seed can also introduce infection into a crop. Identification: Identified on leaves by characteristic light brown circular spots with large yellow margins. Reduces area on leaves for photosynthesis directly reducing crop […]

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Brassica Viruses

General: 3 main viruses affecting Brassicas found throughout New Zealand are Beet Western Yellows Virus Cauliflower Mosaic Virus and Turnip Mosaic Virus. Early infection with any of these viruses can cause severe crop damage. They all use Aphid as a vector to be introduced to crops. Identification: Beet Western Yellow Virus has characteristic damage by […]

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Dry Rot

Technical Name: Leptosphaeria Maculans General: Dry Rot can be very destructive causing 100% crop loss in some instances. Dry Rot over-winters in infected crop residue and spores can spread up to 1-2 km following rain. Dry Rot enters bulbs and stems through growth cracks or insect feeding wounds. Although not common infected seed can introduce […]

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Grass Rust

Grass Rust

Technical Name: Puccinia graminis General: Occurs throughout New Zealand Stem rust affects Ryegrass and Tall Fescue species. Mainly found in warm dry conditions in summer and autumn. Identification: Produces characteristic brick-red powdery spots on leaves and stems. Spores that are carried by wind or rain to other plants.

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Club Root

Club Root

Technical Name: Plasmodiophora Brassicae General: Most destructive disease of Brassicas and affects most Brassicas species. Causes galls to form on roots reducing nutrient uptake and reducing yield. Severe and uncontrolled outbreaks can completely destroy crops. Club Root can remain dormant in the soil for many years as spores. Identification: Symptoms include plants wilting in the […]

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Damping Off

Technical Name: Pythium and Fusarium spp General: Seedling Brassicas can be attacked by damping off which covers a range of fungi that cause plant death and gaps in establishing crops. Causal pathogens are Pythium and Fusarium spp. In the North Island and Rhizoctonia solani in the South Island. Early infections are known as damping off […]

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Bacterial Soft Rot

Bacterial Soft Rot

Technical Name: Erwinia carotovora General: Causes damage as a secondary invader. This means that it can cause additional damage to an original infection (e.g. dry rot) or insect/weather damage as it is a secondary invader disease. Identification: Produces a soft watery light brown/grey rot often with an unpleasant odour. Mostly soil-borne and enters the host […]

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