Manitoba Agriculture, Food and Rural Initiatives (MAFRI) advises that last week the fungal disease ‘late blight’ was discovered on tomato seedlings at several retail locations in Winnipeg and Brandon, raising concerns in Manitoba’s potato industry.
This fungus is a serious disease issue for vegetables and weeds in the nightshade family that includes tomatoes and potatoes.
The retail outlets involved have stopped selling the tomato plants. In order to identify the source of the infestation, plant suppliers have also been notified and action has been taken to prevent further distribution of infected plants.
Some infected tomato plants will have been purchased by the public and planted in local gardens. Under favourable conditions, the spores on infected plants can be carried to nearby fields primarily by wind and infect other plants like potatoes. Manitoba has a significant potato industry and the spread of this blight could jeopardize the quality and market value of this year’s crop.
The blight does not create any human health issues. All above-ground parts of the tomato plant (leaves, stems and fruits) can be infected by the fungus. Late blight manifests as lesions and grey-green areas on leaves. With high humidity, white mildew will be evident on the underside of leaves. In severe cases, complete and rapid blighting of foliage can occur. As tomato plants mature, blemishes appear on the fruit making them unattractive to consumers.
Home gardeners should inspect their tomatoes and potatoes immediately. If late blight is present, destruction by uprooting and bagging infected plants is the best option to prevent further spread to healthy plants. Pictures of tomato plants with late blight can be found online.
Commercial potato growers should apply protectant fungicide on their crops as soon as possible and then scouting their fields. It is also important that commercial growers check their own home-garden plots for infection on tomato and other plants in the nightshade family.
For more information contact, MAFRI’s Crops Knowledge Centre at 204-745-5630.
