Late blight, destructive of yield!

What is mildew?

Potato downy mildew is a fungal disease caused by a fungus, phytophtora infestans. A fungal disease, or fungal disease, is a disease caused to a plant by a fungus.

This disease was responsible for the Irish famine from 1845 to 1852. A disaster with a very important demographic and social balance sheet that illustrates the ability of late blight to spread very quickly and cause a very significant loss of yield.

What are the signs of the development of late blight?

The leaves are affected on the upper and lower surfaces. They have brown spots of oily appearance. On the underside of the leaves, white felting is often visible, corresponding to the fruiting bodies of the fungus. When the disease is sufficiently developed, it can cause the destruction of foliage. Brown spots can often be seen on stems and bouquets as well.

Favorable condition for its development: 

Downy mildew develops in a humid environment (humidity greater than 90%) and when temperatures are high enough (10 to 25 ° C).

Periods of fog and stormy rain therefore present a high risk. Similarly, it will be necessary to reason the watering, another factor favorable to the development of mildew on the plot. 

Late blight is a "focus" disease. After the first plants are reached, if the climatic conditions are favorable and the disease is not treated in time, late blight will spread, like wildfire. That is why the first thing to do is to monitor your plants when the conditions for the development of the disease are favorable.

How to fight against late blight?

In prevention, the farmer will be able to choose varieties that are not very sensitive to late blight such as Passion or Désirée. He will ensure that an average humidity level is maintained on the potato plot. The plants will be sown spaced apart, weeding regularly to counter the development of weeds. Watering, if necessary, will preferably be carried out in the morning. In general, crop rotation will be preferred as well as waste destruction.   

For pest control, several fungicides can be applied to crops, both preventively and curatively. It is recommended to alternate families of chemicals, so as not to encourage the development of resistant strains of late blight.  

Cymoxanil-based penetrating products or sodium bicarbonate can be used to combat late blight.