Tyumen gardeners risk losing tomatoes to diseases. How to save the harvest?

Heavy rains this summer could leave Tyumen gardeners without a vegetable harvest. Nighttime temperature swings also negatively affect plant growth and development. Tomatoes are among the most finicky crops. Svetlana Shabalina, an agronomist at the Tyumen region branch of the Federal State Budgetary Institution Rosselkhoztsentr, explained which diseases often affect them and how to combat them.

“Tomatoes are one of the most finicky crops under high-humidity conditions. Dense planting, poor ventilation, and prolonged rains turn greenhouses and open ground into incubators for dangerous infections,” the specialist explains.

Late blight (phytophthora)

Dark brown blurry spots, often with a yellowish border, appear on leaves. On the underside of leaves in wet weather, a whitish cobweb-like coating is visible — spores of the pathogen. Stems become covered with elongated dark streaks and begin to rot. Hard brown spots form on fruits and quickly enlarge. The fruits become inedible.

The disease spreads rapidly — from the first signs to the death of the entire plant takes five to seven days.

Late blight develops during cool nights and warm days combined with high humidity. The consequences can include losing the entire harvest within a few weeks. Phytophthora spores winter in the soil and on plant debris, infecting plantings the following season.

The agronomist warns that crop rotation is important: do not plant tomatoes after potatoes or other nightshades. Tomatoes should be returned to the same spot no earlier than three to four years later.

Shabalina advises maintaining a distance of 40–50 centimeters (16–20 inches) between plants and removing lower leaves to improve ventilation.

“Water only at the root. Preferably in the morning, so the soil dries out by evening,” she adds.

In July, spray plantings with Ridomil Gold, Profit Gold, or Ordan preparations. Repeat after 10–14 days. This should be done even if there are no signs of disease. As a folk remedy, spraying with a garlic infusion works. Grind 200 grams of garlic into 10 liters of water. Let it steep for a day.

Cladosporiosis (brown spot)

“Yellowish spots appear on the inner side of lower leaves and gradually turn brown. A velvety olive-brown coating forms on the underside. Leaves curl, dry out, and fall off. The disease quickly moves up the plant. Fruits are usually not affected, but due to leaf loss, they do not ripen,” the agronomist describes the process.

The disease develops under high humidity in greenhouses with insufficient ventilation. The optimal temperature for the fungus is +22…+25 °C (72–77 °F). This can lead to losses of up to 50% of the harvest due to premature drying of plants.

For prevention and treatment, Svetlana Shabalina advises ventilating the greenhouse. This is especially necessary after watering. Do not allow plantings to become dense. At the first signs of the disease, remove affected leaves and burn them. Treat with Abiga-Pik, Khom, or 1% Bordeaux mixture. Repeat after ten days. For preventive purposes, also use biological preparations Fitosporin-M and Alirin-B.

Blossom end rot

It occurs due to calcium deficiency and improper watering. A dark watery spot appears on the top of green or beginning-to-ripen fruits. It quickly enlarges, becomes brown or black, hard, and sunken. Affected fruits stop growing and often crack. Secondary bacterial and fungal infections can cause complete rotting of the fruit.

The disease can destroy up to 30–40% of the harvest, especially in large-fruited varieties.

For prevention, Shabalina advises maintaining even soil moisture — water regularly and avoid both drying out and waterlogging.

“Mulch the soil with straw or mowed grass to retain moisture. Apply a foliar feeding with calcium nitrate — 20 grams per ten liters of water,” the agronomist added.

Earlier, we published recommendations from a Tyumen agronomist on how to save fruit trees from diseases. Read what to do in this article.