To grow tomatoes, it is necessary to make a lot of efforts from the very beginning: to choose the right seeds, to grow out seedlings from them, plant seedlings in the ground, water and feed the plants. And one day, when, it would seem, it remains only to harvest, you suddenly find that the tomato bushes began to dry, and the immature fruits themselves have turned black. How does this happen? Why do blackened green tomatoes in the open ground and in the greenhouse, at what temperature does this occur?
There may be several reasons for this. This may be gray or vertex rot , which occurs when a deficiency of some minerals, in particular, calcium. In addition, tomatoes turn black on the bushes because of the increased acidity of the soil. You may have "overfed" plants with fertilizers containing nitrogen. But most often tomatoes turn black when infected with phytophthora - a fungal disease that spreads to some vegetables, including potatoes.
Especially quickly, late blight develops in rainy, wet weather. In the beginning, the disease appears on the tomato leaves: the upper part is covered with brown spots, and the lower one - with a gray bloom. Gradually, the leaves of the tomato turn black, and then the green fruits begin to darken. Sometimes it may seem that the phytophthora has not struck fruit, but as they mature, brown spots appear on them, the tomato rotates from within and is no longer usable.
The disease begins to spread especially quickly in July-August, when fogs appear, abundant dew fall out, the difference between daytime and night temperatures increases.
Measures to prevent late blight
Prevention of phytophthora should be done long before it appeared in your garden. First of all, it is necessary to observe a crop rotation in your area: in no case should you plant tomatoes after potatoes or near it. In addition, it is important to comply with the optimal density of planting a tomato, weed regularly weed, remove all diseased or fading leaves.
It is equally important in order to prevent diseases of a tomato in time to go in and tie hives of tall varieties. In this case, from the soil to the lower leaves of the plant should be no less than fifteen centimeters. In the thinned crone, there will be enough air, which will prevent the occurrence of fungal diseases.
You can also carry out chemical preventive maintenance of late blight tomato: after flowering, treat tomato bushes with Acrobat, Metaxyl or Zaslon solutions. Then, as the bushes grow tomato, they must be treated with a solution of any of the fungicides, which includes copper.
Widely known is the popular way - to pierce the stem of a tomato with copper wire at a height of about 15 cm from the ground. Nutrients will go up the stalk and carry copper ions, which serve as an obstacle to the development of fungal diseases.
What if the tomatoes turn black?
If, despite all the preventive measures, the leaves still dry on the tomatoes, and the tips of the fruits turn black from below, so you need to urgently begin the struggle for the safety of the crop. To do this, choose one of the overcast days and spray the tomato bushes with a solution of calcium chloride or simply with a warm saline solution. On the tomato salt film is formed, which will protect a healthy
After it has rained, sprinkle diseased plants with 1% solution of Bordeaux fluids, which does not penetrate into the plants themselves, and therefore into the human body will not fall.
There are many folk ways to combat late blight. You can treat tomato bushes with garlic infusion, a mixture of yogurt or curdled milk with water.
Cut and destroy completely damaged tomato bushes, and cut the fruits green. Before placing such tomatoes on maturation, they must be treated with hot water at a temperature of up to 70 ° C.