Phytophthora on tomatoes

The outbreak of this infection always begins unexpectedly. And it is important for us to meet it fully armed so as not to lose the harvest.

What does phytophthora look like on tomatoes

As the famous song says, you will recognize it from a thousand. At some point, all parts of the plant become covered with brown spots without clear boundaries and shapes. They cover the bushes like a fire. In wet weather, the leaves get wet, on fine days they dry up.

The disease, as a rule, begins with the lower leaves, then rises up the plant and eventually affects the fruits – the tomatoes begin to rot right on the bushes. And then the leaves begin to crumble and as a result the tops darken and dry out.

In favorable years for the disease, they are able to kill the plant in just a couple of weeks. This is the most dangerous disease of tomatoes.

For the active development of late blight, 2 conditions are needed: high humidity (above 76%, but optimally – 90%) and low temperature (about 20 ° C). At humidity below 76% and temperature above 26 ° C, the development of the disease stops.

That is why the peak of the disease falls on the second half of the summer. At the end of July – August, it is warm and dry during the day, but the nights are already cool and dew often falls in the morning. And these are already ideal conditions for a pathogen. But there are a number of factors that can accelerate the development of the disease.

Rain. Phytophthora spores are in the soil – there they can remain for several years in anticipation of suitable conditions. During rain, splashes, along with soil particles and spores, fall on the lower leaves, and the disease begins to develop.

Wrong watering. The same thing happens if you water tomatoes from a hose with a sprayer or a strong jet.

susceptible varieties. The statistics are sad – 86,2% (1) of tomato varieties are susceptible to late blight. Under favorable conditions for a pathogenic fungus, they will definitely get sick.

How to deal with late blight on tomatoes with folk remedies

Many summer residents are afraid to use chemicals on the site, they want to get environmentally friendly products and therefore I use folk remedies. There are many. But are they effective?

Greenhouse

To combat late blight in greenhouses, you can find a lot of folk advice, but one is in the lead – recently many summer residents have begun to actively use it.

Iodine from phytophthora

Another popular tip, and it is actively recommended for greenhouses. Say, you need to hang open vials of iodine under the roof, it will begin to evaporate, sterilize the air and there will be no phytophthora. Unfortunately, this is another misconception, phytophthora, sorry for the pun, purple to your iodine.

But for a person, iodine vapor is dangerous – they can cause poisoning. At best, you will get off with a cough, runny nose, dizziness and headache. But there may be more severe consequences up to hallucinations, seizures and toxic hepatitis. And given the fact that many summer residents are so fond of iodine that their greenhouse resembles a Christmas tree – everything is literally hung with bubbles – intoxication can become a real problem.

Outdoor ground

It is pointless to hang bubbles with iodine over the beds, therefore, for open ground, craftsmen have come up with other ways to fight.

Phytophthora Serum

This folk method takes first place in the ranking of tips. They say that all that is needed is to treat the plants with whey (either milk or kefir) and the disease, as they promise, will go away.

In fact, she will go nowhere – this is a dead poultice. It is impossible to cure late blight with whey, milk or kefir, just as it is impossible to cure a broken leg with a plantain leaf or a heart attack with motherwort decoction. You will only waste time and give the disease a chance to spread more.

Metronidazole from phytophthora

It is not known who first came up with the idea to treat tomatoes with Metronizadol, but there is no point in this.

First, it is used to treat diseases caused by protozoa (amoebae) and a specific genus of bacteria (2). Phytophthora is a fungus.

Secondly, it is a drug for people. No one has ever studied how it affects plants, because it is ridiculous – there are a lot of good disease-fighting agents designed specifically for vegetable crops. And it is not known how Metronidazole behaves in general in nature – what if it accumulates in fruits? We all avoid meat with antibiotics, but at the same time, for some reason, many summer residents use drugs from a pharmacy in the garden.

In the end, imagine this situation: your child picked up lichen somewhere. Deprive – fungus. And there is an excellent remedy for fungal diseases in plants – Bordeaux mixture. But it wouldn’t occur to you to smear an owl child with a Bordeaux mixture? So why drag drugs for people into the garden?

Phytophthora preparations on tomatoes

Bad news: not a single drug helps 100% of phytophthora. The good news is that although the disease cannot be cured, it is possible to greatly slow down its development. And you will have time to harvest tomatoes. But it is important to start treatment as early as possible.

chemical

There are several chemicals that are designed specifically to combat late blight.

Consent. It is a systemic fungicide that penetrates the inside of the plant and therefore is not washed away by rain. For summer residents, it is produced in bottles of 10, 20, 60 and 100 ml. The drug must be diluted in water at the rate of 40 ml per 10 liters. Consumption rate – 5 liters of solution per 1 weave (3).

This remedy is effective at all stages of the development of the disease, but it works best at the first signs of the disease. In general, it is recommended to use it before the onset of the disease – as a preventive measure. During the season, 3 – 4 processing of tomatoes should be done with an interval of 7 – 10 days.

Spraying should be carried out early in the morning or in the evening in the cold – in the heat it quickly evaporates from the surface of the leaves and may not have time to penetrate into the plant.

The last treatment should be carried out 21 days before harvest.

Revus. This drug is recommended for use both for the treatment of the disease, and as a preventive measure. It has a long-lasting protective effect and is not washed off by rain (one hour after treatment). For reliability, it is recommended to process tomatoes 4 times per season with an interval of 1 – 2 weeks (3).

The drug is available in 3 ml plastic ampoules. The ampoule needs to be diluted with 2,5 liters of water – this is enough to process 50 square meters. m.

You can harvest 5 days after processing.

horde. This is a complex preparation consisting of two antifungal components and each has its own mechanism of action, which enhances the effect. It can be used both for the treatment of the disease and for prevention. It is available as a powder in bags of 25 g. The contents of the bag must be dissolved in 5 liters of water for treating tomatoes in open ground or in 8 liters for spraying plants in a greenhouse. Consumption rate – 5 liters per hundred square meters. During the summer, it is recommended to carry out 3 treatments with an interval of 7 – 10 days (3).

After processing, the crop in the beds can be harvested after 5 days, and in greenhouses – after 3 days.

Biological

These drugs are based on bacterial spores that inhibit the development of pathogenic fungi. This is a great option for those who are afraid to use chemistry. Alirin-B, Gamair, Trichoderma Veride 471 and Fitosporin-M have proven themselves best from phytophthora. They are produced in the form of tablets, granules or powder, but they are used in the same way – they are dissolved in water (according to the instructions) and the plants are sprayed.

The main advantage of such drugs is complete safety. That is, the crop can be harvested even on the day of processing. However, they have many disadvantages. Bacteria are living organisms and a certain temperature is important for their development (this information is usually indicated on the packaging). It will be too hot or cool – the drug will not work. Beneficial microorganisms can die if stored for a long time or improperly. They can not be diluted in tap water – chlorine kills bacteria.

And in general, the effectiveness of biological drugs is always lower than that of chemical ones.

Prevention of late blight on tomatoes

Outbreaks of phytophthora can be avoided if you follow simple recommendations for caring for tomatoes.

Mulch the beds. Spores of the pathogenic fungus, as we found out, fall on plants with spray during rains or watering. To avoid this, mulch the beds. You can use rotted sawdust (fresh ones are not good – they absorb nitrogen and the plants will starve) or straw.

Even better, hay. In the process of decomposition, hay bacillus actively develops in it, which releases a natural antibiotic that suppresses the development of phytophthora. That is, you get a double benefit.

Water in the morning. For the development of the fungus, as we remember, moisture and coolness are needed. It is cool at night, and if we also water the beds in the evening, we will create ideal conditions for the disease. Therefore, it is necessary to water the tomatoes in the morning – the high temperature during the day will not allow late blight to breed, and by the evening the topsoil will dry out and the pathogen will not have enough moisture for development.

Ventilate the greenhouse. It is very important that moist air does not stagnate in it – it also provokes outbreaks of the disease.

Observe crop rotation. If you plant tomatoes in the same place from year to year, phytophthora spores will accumulate in the soil and every year the disease will infect plants more and more. Tomatoes can be planted in their original place no earlier than after 4 years.

And you can’t plant tomatoes after other nightshade crops, especially potatoes – late blight affects them too.

Choose resistant varieties. For the future – always study the information about the variety, now there are a lot of tomatoes that are resistant to late blight. This is usually indicated on the seed packet. Breeders recommend varieties that have increased resistance to late blight at the genetic level: Argo, Gaia, Gnome, Grand, Dubrava, Patrice, Chelnok (1, 4). This does not mean that they are not affected by phytophthora at all, but they suffer from it to a lesser extent.

Popular questions and answers

Answered the typical questions of summer residents about phytophthora on tomatoes agronomist-breeder Svetlana Mihailova.

Sources of

1. Skvortsova R.V. Selection of vegetable nightshade crops for open ground of the Non-Black Earth Region of Our Country // dissertation, 1998 https://www.dissercat.com/content/selektsiya-ovoshchnykh-paslenovykh-kultur-dlya-otkrytogo-grunta-nechernozemya-rossii-0
2. Directory of medicines https://www.vidal.ru/drugs/metronidazole
3. State catalog of pesticides and agrochemicals as of July 6, 2021 // Ministry of Agriculture of the Federation https://mcx.gov.ru/ministry/departments/departament-rastenievodstva-mekhanizatsii-khimizatsii-i-zashchity-rasteniy/industry- information/info-gosudarstvennaya-usluga-po-gosudarstvennoy-registratsii-pestitsidov-i-agrokhimikatov/
4. State Register of Breeding Achievements

   https://reestr.gossortrf.ru/