Pathogen: fungus Oidium erysiphoides Fr.
This disease severely weakens the plants, the tomatoes cease to cling, prematurely die. The yield loss level can reach 50%. In this case, powdery mildew affects not only solanaceous, but also other vegetable crops, as well as garden flowers, shrubs and even trees.
Tomato powdery mildew is a fungal disease that is easily recognizable on the characteristic gray-white plague, which looks like dew droplets (hence the name). In addition, stains can also hide the stalks and fruit of the plant. But basically the infection is located closer to the soil, where moisture is higher. Its development of mildew begins with the first summer heat at temperature of 15С and above, as well as at low humidity, or poor watering.
After infestation on the outer side of the leaves, mainly on the top of the plant, yellow and light green spots of round shape begin to appear, and on the back of the fungus layer. As the disease progresses, the spots grow, and the fungal inflammation becomes noticeable on the front side of the leaf.
If, at the first stage, no action was taken to remove powdery mildew from the crop, then very soon the disease spreads to the lower tiers of the plant and begins sporulation. The affected areas of tomato gradually dry up and die. When aggressive development of the disease, the plant can throw leaves and die.
The spores of the fungus are spread by airflows, and at long distances, also in direct contact with diseased plants and with splashes of water (for example, during irrigation). Infected tomatoes with powdery mildew contribute to sharp fluctuations in temperature and high humidity of air. Less tendency to disease in plants appears due to the excessive amount of introduced nitrogen fertilizers.
For the prevention of powdery mildew of tomatoes, the following methods are used: