Phytophthora - treatment and prevention

Phytophthora is not only one of the most common but also the most dangerous diseases on our favorite tomatoes and potatoes. It appears imperceptibly and spreads surprisingly quickly through the beds. And it is dangerous not only in the middle of the wet summer. It is worth losing vigilance, and phytophthora will lose such a long-awaited harvest in a matter of days. Phytophthora prevention and control require a systematic approach. And the right choice of crop protection products that will not lead to the accumulation of toxins in fruits and tubers. After all, while saving vegetables, it is important not to lose their environmental friendliness and nutritional value.

As soon as the long-awaited warmth comes, the time of relentless fight against diseases begins. And among the threats to the future harvest, which is so unfortunate to lose after all the efforts made, there is none more insidious and difficult to recognize in the early stages of the disease than phytophthora.

Life cycle and appearance of late blight

Phytophthora species are destructive organisms. They belong to oomycetes and therefore, strictly speaking, are not fungi. They develop well at a soil temperature of +15 to +23°C and a moisture level above the optimum for crop growth.

Phytophthora overwinters in roots, infected tubers and bulbs or in the soil at various stages: in the form of oospores (overwintering reproduction spores), sporangia (special structures that can either germinate directly or produce zoospores), chlamydospores (thick-walled mycelial cells resistant to desiccation) or mycelium.

Zoospores are spores with flagella that allow them to move through water. Zoospores are formed from overwintering structures that infect the host plant. The infection usually spreads from the root to the root neck. In addition, direct infection of the root neck is possible. The pathogen germinates into the stem and surface of the plant, and new sporangiophores (structures containing sporangia, a type of spore) are formed with sporangia protruding through stomata. Secondary infection occurs through the germination of sporangia, or through zoospores produced in sporangia. For germination on the above-ground parts of plants, the leaf must be moist.

Dispersal by wind and rain causes the pathogen to return to the soil from infected plants. Spread in the soil occurs through water, as zoospores can easily move through water. This explains the fact that the disease spreads faster if the water content of the soil or substrate is higher than normal or optimal for crop growth.

Phytophthora is easily recognized by the fruits, but then the disease is already in the late stages. Phytophthora begins almost imperceptibly. And always from the lower leaves. The first signs do not look suspicious: the leaves turn yellow, dry up, and look little different from greens affected by the sun or strong night chills. And while it is not suspected, phytophthora develops quickly and destroys the plant. Dark brown spots begin to grow strongly on the leaves and stems, and spots of whitish "moldy" fluffy coating appear on the back of the leaves.

The disease becomes obvious with the appearance of grayish or dark, unevenly hardening and deformed marks on tubers and fruits. After dissection of the skin, a brownish-red shade of the affected tissues is visible inside. Even those fruits and tubers that do not have marks on them will quickly be lost after collection to the effects of phytophthora bacterial rots, which spread amazingly quickly.

Phytophthora spores infect plants through stomata, reaching them with water droplets. But once it gets into the body of a plant, a cycle is established: the spores infect the soil, get into new plants, from which they get into the soil again, and everything repeats. It is not easy to break this vicious circle of infections.

It is believed that the phytophthora "season" begins in the second third of summer, but it can become active at any time - as soon as a favorable combination of high humidity, abundance of dew, daily temperature changes, stable heat without extreme heat is established. Moreover, two consecutive rainy days are enough to start spreading.

The ease of reproduction and preservation of phytophthora pathogens is the key to understanding its "success". Infected material may look indistinguishable from healthy material. Spores overwinter perfectly on tubers, tops, fruits and even seeds. They are stored in the remains of plants that were not removed from the soil or put in compost and actively penetrate the soil itself. During the season, pathogens easily spread from affected plants to neighboring areas and plants, are carried with shoes, tools, and equipment. Phytophthora spores can be carried several kilometers through the air.

Phytophthora is considered a disease mainly of nightshades. In addition to the beloved potatoes and tomatoes, which suffer more often and more than others, late blight is also found on peppers and eggplants, less often on garden strawberries, raspberries, apples, citrus fruits, indoor plants, buckwheat and even castor. Phytophthora does not harm plants either in open ground, or in greenhouses, or in pots

Means for fighting phytophthora in the garden

In the battle with phytophthora, it is different products and a comprehensive approach are the best helpers.

Since the disease is very difficult to recognize at the beginning of infection, frequent and careful inspection of plants and leaves is very important. As well as proper care and compliance with the rules of agricultural technology.

Several simple measures can be used to prevent the development of phytophthora:

• protect plants from high humidity by carefully watering under the roots, mulching the soil, weeding and removing leaves below the fruits;
• choose resistant varieties and hybrids;
• treat seeds before sowing;
• carry out preventive spraying;
• do not rush to plant seedlings, waiting for any threats of frost and sudden temperature changes to pass;
• avoid dense planting;
• control the quality and composition of fertilizers, eliminating the risk of nitrogen overdose and overfeeding;
• control the ripening of fruits, collecting fruits of technical or incomplete maturity;
• observe crop rotation, not planting nightshades one after the other in the same place without a safe break;
• cultivate and improve the soil;
• destroy diseased plants, old leaves, tops and damaged fruits immediately (and do not use them in composting).

But one caution is indispensable. Without phytophthora control measures, more than 60% of the crop can be lost. Phytophthora damage is irreversible, but you should not think that fighting it is useless. Simply, the task is not to save the damaged fruits, but to stop the disease and its spread. To reduce damage and the risk of phytophthora spreading, preventive, protective and eradication measures will have to be taken at the same time.

Fungicides of a narrow or wide spectrum of action are used to treat phytophthora. Phytophthora is unique in its ability to adapt very quickly to the means. Old preparations containing copper, Bordeaux liquid and conventional fungicides quickly lose their effectiveness without alternation. And very rarely do they "cover" all three tasks - prevention and treatment, protection and combat - at the same time. The key to the effectiveness of fungicides is strict adherence to the instructions for use.

Therefore, we recommend a systematic approach, starting from the soil, to suppress the pathogens of late blight.
For this, it is necessary to take the preparation Sporomax™ T at the rate of 10-20 g/5-10 l of water per 1 acre, treat the soil and earn (cultivation, milling, digging, etc.).
During the growing season, preventive treatments are carried out with biological fungicides Sporomax™ B and Sporomax™ T in a dosage of 10 g/10 l of water. Starting with seedlings, you can carry out treatments once every 10-14 days.

Bacteria and fungi in the composition of these drugs actively suppress the development of pathogens due to competition for nutrients and direct parasitism on the pathogens themselves. Thanks to this, the phytosanitary condition of the soil and plants improves. Due to the biological basis of Sporamax biofungicides, phytophthora pathogens do not have the factor of developing immunity to the drugs.

For vegetation treatments, we recommend adding Izomax™ 2ml/10l adjuvant to the tank mixture, which will allow the working solution to get into the most difficult places and evenly cover the plants.

If the disease has developed, we recommend treating with chemicals according to the instructions and repeating Sporomax™ B and Sporomax™ T treatment 15-20 days after chemistry.

We wish you good harvest!