by Just yesterday, the cucumber leaves were delighting with their juicy greenery, and today you have discovered telltale white or yellow spots on them? You need to take urgent measures to save the plantings. How to distinguish fungal spots from burns and how to treat the latter – read in this article.
In case of fungal infection, you should spray the cucumbers with a fungicide solution as soon as possible, but if the spots on the leaves are the result of sunburn, then it is worth reviewing agricultural technology and eliminating errors in watering, fertilizing and processing plants. Let’s figure out the details together.
How to distinguish a burn from a fungal disease
The first step is to establish a correct diagnosis: whether the spots on the leaves appeared as a result of a burn or whether this is the “work” of a fungus spreading its spores. A careful examination of the leaves from the front and back will help to understand the cause.
If you find a light or brown coating, small dots, bumps or sticky secretions around the spots and on the back of the leaf, it means that the borage is infected with a fungal infection and needs to be treated with a fungicide.
If, apart from the spots, there is no damage on the leaves, then it is highly likely that their appearance was caused by care errors – watering during the daytime in strong sunlight or careless fertilizing, in which the fertilizer solution could get on the leaves.
Drops of liquid, like lenses, focus the sun’s rays, which leads to the appearance of round light spots that dry out over time. As a result, metabolic processes in the tissues are disrupted, which affects the health and fruiting of the crop.
Burn spots on cucumber leaves, unlike bacterial and fungal marks, have clear boundaries and do not grow or merge over time.
Protecting cucumbers from burns in a greenhouse
The first and most important thing to do to prevent cucumber burns in a greenhouse is to adjust the watering and fertilizing regime. All procedures should be carried out strictly in the morning or evening hours, when solar activity is low. Plants should be watered at the root, trying not to get on the leaves, and foliar feeding and treatments against diseases and pests are best done in the evening or in cloudy weather – then the plants will have enough time to absorb drops of liquid on the leaves.
When grown in a greenhouse, sunburn on cucumbers can occur even with proper watering – morning and evening. The cause is usually drops of condensation that accumulate on the walls and roof of the greenhouse overnight and fall on the leaves during the day. In addition, shiny metal objects (tools, buckets) and containers with water installed to increase humidity can also reflect and intensify the sun’s rays.
Therefore, after watering, the greenhouse must be ventilated – this will help prevent excessive humidity and condensation, and therefore reduce the risk of burns. Do not store equipment (shovels, rippers) in the greenhouse and use metal buckets for water.
Most often, burns on greenhouse cucumbers appear on those leaves that come into contact with polycarbonate or glass. In this case, prevention will be careful tying of the vines so that the leaves do not touch the walls of the greenhouse. You can let them creep along wooden supports, V-shaped twine or tie them up in this way.
Prevention of cucumber burns in open ground
Planting cucumbers in open ground allows you to avoid problems with excessive air humidity and condensation, since in wind-blown beds the aeration of foliage is much better, and the risk of burns and fungal diseases is lower. The exception is periods of unfavorable weather with hot sunny days or excessive temperature drops at night.
To prevent burns in hot weather, it is recommended to shade cucumber beds with light agrofibre or fabric, securing it to support posts along the edges of the bed. In the middle zone, such a need may not arise, but in the southern regions, where the sun is much more active, the construction of a shelter is a prerequisite for growing cucumbers (as, incidentally, most other crops).
You can kill two birds with one stone by building a trellis to support cucumber vines and covering it with netting or fabric.
The rules for watering and processing borage in open ground will be the same as for greenhouse plantings: watering under the root with settled, non-cold water, irrigation on the leaves (sprinkling) is allowed only during periods of drought, but at a comfortable moderately warm temperature, since in the heat, burns may appear on wet leaves, and in cool weather – fungi.
The ideal solution for moistening the soil under cucumbers both in a greenhouse and in open beds will be drip irrigation. In combination with mulching, it will help create optimal conditions for the development and active fruiting of cucumbers, while reducing your labor costs.
How to revive cucumbers with burns on the leaves
To stop the leaves from turning yellow and drying out, cucumbers can be treated with a solution of a vitalizer or growth stimulator (Epin-Extra, Yantarin, HB-101) or use one of the folk recipes:
- spray with a milk-soap solution (dissolve 10 liter of milk, 1 drops of iodine and 30 g of laundry soap in 20 liters of water, repeat the treatment every 10 days);
- treat the leaves and pour onion infusion (pour 0,7 l of onion peel into 10 l of water, bring to a boil and leave under a lid for 14 hours, then strain and dilute with water 1:4);
- spray with a 1% solution of potassium permanganate.
To strengthen plants and increase their defenses, it will be useful to feed damaged bushes with a solution of complex mineral fertilizer (prepare the solution according to the instructions and water it under the root). In the first half of the growing season, it is better to take a complex with an increased rate of nitrogen, in the second – with an increased content of phosphorus and potassium.
Organic feeding with one of the folk remedies will have an excellent effect on the condition of cucumbers: mullein, herbal or ash infusion. Mullein (1 kg per 3 l of water) is infused for three days and diluted 1:3 before use. Chopped grass (1 kg per 10 l of water) is infused for a week, the resulting concentrate is diluted with clean water in a ratio of 1:9 – this solution can be sprayed and watered under the root. Wood ash infusion (1 l of dry matter per 10 l of water) is prepared for two days, and it can also be used for watering and spraying on the leaves.
If you notice drying spots on cucumber leaves, do not rush to grab a sprayer and treat the plantings with strong fungicides. Perhaps your cucumbers are only slightly “burned” in the sun, and you can help them by adjusting the watering regime and nitrogen fertilizing.
