With that, if you still have late blight on the potatoes in your garden, try peanuts!
Reference:Department of Agriculture and Aquaculture Canada
Potato late blight is a fungal disease originating in Mexico, which spread to Europe and North America around 1845. Late blight caused epidemics and famine in Ireland, where the population lived off the potato harvest. Potato late blight was reported in the Maritimes between 1845 and 1847.
Recently, new lineages of the disease have emerged in the Maritimes. These lines are more aggressive than previously known ones, since they infect plants earlier in the season, cause greater damage and persist during periods of dry weather.
Late blight is caused by the fungus Phytophthora infestans . Three risk factors must be present for infection to occur:
Late blight survives from season to season in infected tubers. Infected potatoes that are in storage, as well as infected tubers that do not freeze over winter in the garden or in the compost, are all new sources of infection. Infected tomatoes, tossed in the compost in late winter or early spring, could also be a source of infection if they don't freeze. The wind carries the spores of late blight to the new shoots of potatoes or tomatoes. Spores can be transported 80 km or more from a source, but it is common for them to travel 8 to 16 km.
Members of the nightshade family are susceptible to downy mildew. This family includes potatoes, tomatoes and peppers, all of which are at risk of infection with late blight. Some potato varieties are less susceptible than others, but none are immune to the disease. Recent advances in genetic engineering may soon provide us with improved varieties with a high level of resistance to downy mildew.
The development and spread of late blight is favored by cool, wet conditions or by prolonged periods of rain. Nighttime temperatures of 10 to 15 o C, and daytime temperatures of 15 to 20 o C, humidity over 90% and cumulative rainfall of 30 mm or more in the last ten days, are conditions conducive to the development and spread of late blight.
The spores land on leaves, stems or fruit, and infect the plant if it gets wet. Infection is seen in the lesions that are visible after four or five days. Infected leaves develop dark green watery spots that enlarge and turn dark brown with a pale green border. The spore-producing region, white and delicate in appearance, can be distinguished outside the lesions on the underside of the leaves. In conditions of 90% humidity, late blight spores develop in seven to ten hours. Dark lesions with white sporulation also appear on the stems, often at the base of the leaves.
Late blight spores, when washed to the ground by heavy rains, can infect tubers. The infected tissue becomes grainy, red in color and can reach 2 cm in depth. A white spore mass is sometimes seen on tubers stored in high humidity storage.
Similar symptoms appear on the leaves and stems of tomato plants. The surface of infected fruits first shows pale brown spots, then the spots enlarge and become darker and wrinkled. These spots usually occur on the top of the fruit.
Do not use your own potatoes or those from the grocery store for your seeds. Buy inspected and certified seed potatoes instead.
Seed potatoes should be inspected before planting, and any seed showing signs of rot should be discarded.
The first mildew infections often appear in early to mid-August . Avoid disease by favoring an early harvest:
Do not leave old potatoes or old tomatoes exposed in a compost bin. Remove and bury seedlings that begin to grow in the compost.
Remove the volunteers, from the previous year's potatoes, which have survived the winter.
Ensure as dry an environment as possible for the potato and tomato plants, promoting greater air circulation:
Do not use too much nitrogen fertilizer, as this fertilizer promotes leaf growth, decreases disease resistance and delays ripening.
Plant tomatoes as far away from the potatoes in your garden as possible.
Mound the potato plants well to better protect them against spores that could penetrate the soil and infect the tubers.
If you choose to use fungicides on potatoes and tomatoes, weekly applications, started early in the season, will help delay early infections and slow disease progress.
Remove infected leaves or stems daily to reduce spore production and risk of spread. This method could be effective if the weather turns dry and slows disease progression.
If you cannot control the disease, choose a dry, sunny day when you will remove all the potato plants:to do this, stand with your two feet on either side of the stems, and pull all the stems at the same time. Take care not to dig up the tubers. Place stems and leaves in tightly sealed garbage bags. The tubers can thus remain in the ground, protected from infection, until the fall. Wait at least two weeks after removing the tops to harvest.
As a replacement for Bordeaux mixture which has bad consequences on the life of the soil in the event of repeated applications (especially since copper cannot be leached and concentrations in the soil are very important), the use of horsetail manure gives interesting results.
And to continue reading here is the following according to a study over 4 years (1999 – 2002) FREDON Nord-Pas de Calais
To prevent potato late blight :
Before planting:
During cultivation
Potato varieties resistant to late blight:
– Aziza, Ballade, Bondeville, Corolle, Eden, Gasoré, Innovator, Naturella, Raja, Santé.
Medium resistant varieties
– Caesar, Santana,
Susceptible to very susceptible varieties
– Agata, Artemis, Bintje, Charlotte, Chérie, Daisy, Franceline, Russet, Shepody, Victoria
Treatments against downy mildew:
Replacing Bordeaux mixture which has bad consequences on the life of the soil in the event of repeated applications (especially since copper is not leachable and the concentrations in the soil are very high in the long run) , the use of horsetail manure gives interesting results.
