The word “Phytophthora” makes gardeners and gardeners shudder — just not again.! And – run to your plants: check, look around, evaluate and take action. And so it is every year, especially in regions where summer is short, with August rains.
Why is there still no means to destroy this pernicious disease of tomatoes and potatoes in order to get rid of it forever? It seems to me that late blight is like a spy and a saboteur at the same time: it can sneak up on you and hit you powerfully, it has a good ability to dodge and hide.
A little about the causative agent
Late blight is a fungal disease that causes it, Phytophthora infestans. Phytopathology, studying the pathogen, reveals an extraordinary ability to survive. For example, it lives in plants and on plants, not just in water.
The pathogen of phytophthora lives in plants and on plants, and also does not die in water
It has mycelium, like any mushroom, it spreads (grows) in the cells and intercellular fluid of the plant. It has an extraordinary mushroom – zoosporangium, zoospores are formed in it – this is the stage of the life cycle. From zoospores that begin to divide, a new mycelium grows, asexual reproduction occurs. However, phytophthora has the possibility of sexual reproduction. In this case, there are zoospores, they are at rest, unlike zoospores, which are also called vagrants. Zoospores infect plants and cause diseases. Zoospores also lead to diseases if they germinate.
As late blight can infect plants
The main place of wintering is tubers that are affected by the pathogen. He peacefully “slept” while the tubers were stored. And as soon as you put them on germination, the mycelium will immediately spread into new potato plants. So it is transmitted from one plant to another according to a scheme developed over millennia. At the same time, potato plants are infected, and only two weeks after the potato disease, the disease affects tomatoes.
Also, an infection may persist in the soil if you leave diseased plants or part of the crop in which zoospores have been preserved. Then both tomato and potato plants will be affected at the same time.
However, it happens that tomatoes begin to hurt earlier. This can happen if infected soil (with plant residues) from greenhouses gets into the open ground with seedlings.
What makes the pathogen in the plant
To live, every living organism must eat. The pathogen of phytophthora is no exception. He needs plants for this important purpose. The consequence of such feeding is a change in respiration, a change in mineral nutrition, water absorption, that is, the plant weakens and aging begins. Earlier aging, rather than aging by the age of the plant. Also, the plant can quickly “age” if there is less chlorophyll in the leaves, if photosynthesis decreases, if nutrients do not accumulate.
The disease attacks
It is believed that the seeds from the plant you have collected cannot give a full harvest. Seeds from such plants cannot be taken, they may be infected. Potato tubers cannot be taken for seeds either.
Plant feeding
It is usually said that there are weather factors that contribute to the progression of the disease. This is dew and fog, when the smallest droplets of water settle on the leaves of plants, and the humidity is high and more than + 15 ° C … + 22 ° C (59-71.6°F) heat. The most unfavorable weather conditions for plants, but the most favorable for phytophthora.
It would seem that top dressing should help plants resist the onslaught of the aggressor. However, fertilizer containing nitrogen, on the contrary, worsens their condition. Plants are severely affected and may die.
Races of Phytophthora
Phytophthora has species. They are aggressive towards plants and are at war with each other.
In gardens, as a rule, potato and tomato beds are always located side by side, because the plots are small, and it is not possible to geographically separate potato fields from tomato fields, as is done in large farms. That is, there is no spatial isolation of plantings of different cultures. If the farmer also divides his beds somehow, then there is no guarantee that the neighbor will not attach his sick plants nearby.
The first spots
It’s a kind of mix of racing in the rain and high humidity. Then an epidemic begins, which has its own name for plants – an epidemic. This is a massive progression of the disease in a certain area. Another race can be dominant or main, sometimes one race displaces another.
It is important that plants find it difficult to survive in the fight against various aggressors. There are varieties of tomatoes more resistant to phytophthora, there are less resistant. Even very resistant varieties of plants can be damaged during mass destruction. First, more susceptible ones are affected, and then pathogenic microorganisms can move to more stable ones.
Some of the fruits ripened before the invasion of phytophthora
If you grow only stable varieties, the aggressiveness of the pathogen will decrease. It is hoped that breeders will breed varieties for which late blight will not be a problem, because work is underway to select for resistance to diseases. But this is a matter of the near future.
Fast-growing varieties of tomatoes
They yield crops before the time of the phytophthora attack. There are varieties with some resistance – they may not suffer from phytophthora in quiet years, but during epiphytotic they also become infected.
How to adjust to the habits of Phytophthora
The weather is often unpredictable, we cannot understand its plans.
Phytophthora destroyed the fruits
We cannot predict what precipitation will be in our area and how long it will be. Therefore, the main strategy is prevention. If the weather is like this, then you can anticipate the attack of phytophthora; plant treatment should be carried out ahead of time, without waiting for the first spots on the leaves to appear. It is necessary to start with systemic contact preparations, in this case fungicides are well suited. A contact fungicide will be ineffective, as it is washed off by rain.
In confidence
In the struggle for the harvest, farmers are trying different drugs, including medical ones. It is unlikely that agronomists will advise them, but after all, gardeners are allowed on the site everything that is not prohibited by law. Therefore, as a preventive measure, they try to fight with any acceptable means: serum, bacterial preparations…
The list of effective remedies can also be borrowed in the comments, based on the experience of fighting phytophthora by other gardeners.