Why cucumber leaves turn yellow, dry and curl
Sooner or later, every gardener may encounter the same problem cucumber leaves suddenly start to turn yellow, dry out, and sometimes curl up. Why does this happen and how can I prevent cucumber leaves turn yellow? How can you stop it before it’s too late?
In this article, we will consider the causes of yellowing, drying, and curling of cucumber leaves. And also ways to prevent and combat this problem.
WRONG-WAY OF WATERING CUCUMBERS
Watering cucumbers should be done in such a way that there is enough water in the soil, but not too much or not enough. In the absence of moisture, the leaves of cucumbers are guaranteed to turn yellow, and too much moisture in the soil may start to rot the plant itself, in addition to the leaves turning yellow. Ideally, the soil should be kept moderately moist to a depth of about 3.5–4.5inch (9–11cm).
What should I do if the cucumber leaves in the greenhouse or outdoors suddenly start to change color? The first thing to do is to normalize irrigation immediately and determine if the soil is moist enough, excessively dry, or overly wet.
This can easily be checked by digging the soil to a depth of 3.5–4.5inch (9–11cm). The best watering regime in a greenhouse is a bucket of water every 11 square feet, every two or three days. Obviously, watering can be doubled if the weather is hot and cut in half if it is wet and cloudy.
If the soil under the cucumber is too wet, you should definitely stop watering and loosen the entire surface of the soil. You can also sprinkle dry river sand or wood ashes on the soil and they will absorb some of the water.
If the soil under the cucumber is too dry, it should be well watered. Only room temperature water should be used to moisten the soil, and the soil should be loosened before watering to allow the water to penetrate deep into the soil. After watering, cover the soil with a layer of humus about 1 inch thick.
LACK OF FERTILIZER
If there is enough water in the soil but the leaves are yellowing, it means the plant needs to be nourished. Therefore, it is well known that cucumbers should be fed nitrogen fertilizer during active growth, and if there is not enough nitrogen fertilizer, then the leaves will start to turn yellow.
When the leaves start to turn yellow, you can try feeding cucumbers with ammonium nitrate by dissolving 25–30 grams in a bucket of water. The application rate of this solution is about 0.4–0.5 Gal (1.5–2 liters) per 11 square feet.
It is best to spend 2–3 applications of fertilizer on cucumbers, paying attention to the condition of the leaf discs. If the yellowing of the leaves has not subsided, you can feed them with a solution of nitroaminophos by dissolving one tablespoon of this fertilizer in a bucket of water. The consumption rate is 0.8–1 Gal (3–4 liters) per 11 square feet of soil.
If cucumber leaves not only begin to turn yellow but may also curl, this is likely to indicate a severe nitrogen deficiency in the soil. To determine if it is a nitrogen deficiency, you can follow the direction of the cucumber leaf curl. If it curls down, it is definitely a nitrogen deficiency.
You can compensate for a sharp nitrogen shortage by adding 15–18 grams of ammonium nitrate per 11 square feet, pre-dissolved in water. You can treat your own cucumber plants with ammonium nitrate at night by dissolving 8–10 grams of this fertilizer in a bucket of water. It will already be foliar feeding and can produce positive results.
COLD WEATHER
It’s simple. Cold is the worst stress on plants at inopportune times, and they always respond to that stress in the same way by necrosis. Where cucumber leaves yellow, they are necrotic.
When yellow leaves appear on cucumbers, try to bring the temperature in the greenhouse (in the case of open ground, we can’t do anything) to normal levels. The normal temperature for cucumbers in the greenhouse is 73–77°F (23–25°C) on sunny days, 66–70°F (19–21°C) on cloudy days and 60–66°F (16–19°C) at night.
Resulting period 75–77°F (24–25°C) on sunny days, 71–75°F (22–24°C) on cloudy days, and 66–70°F (19–21°C) at night. You can regulate the temperature inside the greenhouse by installing heaters (to raise the temperature) or by opening the windows and doors (to lower the temperature).
BURNING SUN
It is not the sun itself that usually damages cucumber leaves but in combination with other factors. It is often our own fault, and the sun only makes the situation worse.
For example, if we water a cucumber plant in high temperatures, the water that accumulates on the leaf plate acts as a lens: the light passes through it and burns the leaf tissue. The second variant is a short period of rain that leaves tiny droplets on the leaves, which boil and evaporate from the cucumber leaves after the sun goes out from behind the clouds, leaving burns.
Here is one. Do not water the leaves of the plant in the heat, watering is best done in the morning and in the evening, and in the morning you should try not to water on the leaf discs. In the greenhouse, in order not to accumulate condensation falling on the leaves of cucumbers, you need to open the windows and lower the humidity and temperature to prevent its appearance.
VARIOUS CUCUMBER DISEASES
The most common of a long list of diseases that cause yellowing of the leaf plate is fungal, such as powdery mildew. In addition to discoloration of the leaf layer, it causes it to dry out and curl.
Powdery mildew appears as a powdery coating on the upper side of the leaves. In this case, the plants should be treated with a copper-based preparation (Bordeaux mixture) or a fungicide.
If distinct yellow-brown spots are found on the leaves, the plants should be treated with 1% colloidal sulfur. This spot, followed by drying and curing of the leaves, leads to anthracnose.
As a rule, one treatment may not be enough; in this case, the plants should be treated again after a few weeks, but this time with 1% Bordeaux mixture. After a few days, the effect can be consolidated by applying copper sulfate (0.5% solution) directly to the infected spots or by covering them with crushed charcoal.
If round yellow spots appear on the cucumber leaves and the leaves start to wilt, turn over the affected leaves and you will see a layer of white powder on the back, this is false powdery mildew. Immediately after spotting the spots, you must stop watering for a week or so and then treat the plants with a fungicide at a rate of 18–22 grams per bucket of water.
If you are at least a month away from flowering and fruiting, you can treat the plants with a “bacterial fungicide + biopesticide” (two tablespoons per bucket of water). Treatment with these preparations should be carried out strictly in the spring. Do not forget to remove all traction from the plot in autumn and replant cucumbers in this area, not earlier than 5–6 years.
CUCUMBER PESTS
Various pests of cucumber plants, such as aphids and spider mites, suck the sap from the leaf tissue, causing it to turn yellow and eventually — curl and dry out.
You can tell it’s the first by the color of the cucumber leaves, which become pale at first, then turn yellow and curl up, and second by the presence of the pests themselves.
Swarms of aphids are easy to spot — you just have to turn the small leaves over, but mites are harder to spot — you usually know it’s a mite attacking a cucumber by the spider webs on the back of the leaf.
In the case of aphids, it can help to have all the same nitrophos card — 2 tablespoons per bucket of water, but with spider mites, you can treat with colloidal sulfur — 75–85 grams per bucket of water.
CUCUMBER ROOT INJURIES
The roots of cucumbers can be injured as pests, and you and I — break them due to unskilled actions when planting seedlings or during weeding or loosening the soil.
If cucumber roots are injured from loosening soil, you should feed the plants a nitrogen fertilizer (5–7 grams of ammonium nitrate per 0.25 Gal of water — a rate of 11 square feet per) and then gently whack them about 1 inch.
YELLOWING OF CUCUMBERS AND WILTING OF LOWER LEAVES
We’ve figured out what and how to eliminate yellowing, shriveling, and wilting of the main, large leaf discs of cucumbers, but often we see the following: the main leaves look healthy, but the lower, smaller leaf discs of the cucumber suddenly start to turn yellow and wilt. Gardeners sound the alarm, not knowing the cause of this phenomenon, but is it really that dangerous?
The most common cause of yellowing of just the lower leaf plates of cucumbers is lack of light. The taller, stronger leaves just get in the way, while the lower leaves die when they are not needed.
In this case, there is no need to sound the alarm; you can simply remove the yellowing and beginning to wilt cucumber leaves; the plant simply doesn’t need them anymore.
The second reason is a possible deficiency of trace elements such as magnesium or large amounts of nutrients such as potassium and phosphorus.
In this case, you need to apply a fertilizer compound containing micronutrients. The application rate is 12–15 grams per 11 square feet. Sometimes it helps to apply wood ash, which is an excellent potash fertilizer that also contains micronutrients. Under each shrub, pre-hydrated and watered soil, you need to make 50–100 grams of wood ash.
The third reason is the natural aging of the plant. If the lower leaves of cucumbers begin to turn yellow near the end of the season, then you should not worry, it is likely that they are wilting, because the lowest leaf plates are older.
In this case, again the best option is to remove the cucumber’s leaf plates to prevent them from starting to rot.
If none of this helps, you should check that the plants are not getting in each other’s way and are not placed so close together that the leaf clusters of some plants are strongly overshadowing the plants next to them. If this is indeed the case, you will have to take drastic measures — remove part of the cucumber stems or even the whole plant.
METHODS OF REGENERATION OF CUCUMBER LEAVES
So, we have considered the different causes of yellow and dead leaves on cucumber plants, but sometimes it happens that none of these causes are suitable, then you can use universal methods to restore the normal appearance of the leaf discs.
The most reliable method is to treat cucumbers with a combination that fights pests and enriches the plant with minerals at the same time.
Option 1: a mixture of milk and soap. It is necessary to add 0.25 Gal (1 liter) of milk, 30 grams of laundry soap, and 40 drops of iodine to a bucket of water. It is important to stir the soap until it dissolves and it will act as a “sticker”. Once the first yellow leaves appear, you should treat the cucumber with this solution once every two weeks until the yellow leaves disappear.
Second option: infusion of bread and iodine. Soak a whole loaf of rye bread in a bucket of water for 15–20 hours, then add 60–70 drops of iodine to the solution, strain it, and you can treat your cucumbers with this infusion every 12–14 days.
Option 3: Soak onion shells. It is necessary to take 500–600 grams of onion shells and pour them into a bucket of water. This container should be brought to a boil, then removed from the fire, covered with a thick lid, and left for 12–15 hours. It is still filtered, diluted by half with water, and you can either treat the plant or water it under the bushes, spending 250–300 grams.
HOW TO AVOID THE YELLOWING OF CUCUMBER LEAVES?
Finally, let’s talk about useful ingredients that help prevent the premature yellowing of cucumber leaves.
The first is the herbal infusion of comfrey, which is the safest and most useful fertilizer. And note that cucumbers respond best to feeding with comfrey. To make such a feeding, you need about a kilogram of fresh comfrey chopped fine and poured into a bucket of water, then about a week to soak.
Then filter the infusion, dilute it three times and use it for spraying (0.5–0.8 Gal per 11 square feet) and fertilizing (500–600 grams per plant).
This fertilizer combines very well with wood ash. The procedure is as follows — first loosen the soil, water with this green fertilizer, then sprinkle with wood ash and spread a 0.4inch (1cm) layer.
A solution of common baking soda can be used as a preventive measure against various fungal diseases. Dilute one tablespoon of baking soda in a bucket of water and treat cucumbers with this solution, using 0.25 Gal (1 liter) per 11 square feet and trying to reach both surfaces of the leaf disc.
Quite effective in this regard is a solution of urea, in addition, it is a good foliar spray of ammonia. You need to dissolve 35–45 g of urea in a bucket of water and treat the plants, using 0.25 Gal (1 liter) solution per plant.
Sour milk solution also has an antifungal effect. You need to dilute yogurt or whey in half and then treat it while wetting both sides of the cucumber leaves.
A good means of preventing powdery mildew, and also a good way to foliar spray cucumbers, is to use a cowpea infusion. It requires 2.2 Lb (1 kg) of manure dissolved in 0.8 Gal (3 L) of water, giving him a day to soak.
The infusion should then be filtered, diluted three times with water, and treated at a cost, using 0.4–0.5 Gal (1.5–2 Lb) per 11 sq ft.
Infusion of wood ash or furnace ash is slightly less effective, but still prevents powdery mildew and associated yellowing of cucumber leaves, and provides potassium to the plant. It is prepared by dissolving 500–600 g of wood ash or 250–300 g of soot in a bucket of water and letting it sit for 25–30 hours.
After this infusion, preferably filtered, you can treat the plants with it, trying to hit both surfaces of the leaf plate, 0.25 Gal (1 liter) per clump of flowers.
That’s all we wanted to tell you about the causes of yellowing and wilting of cucumber leaves and ways to solve this problem. We hope we have helped you. If you have any questions, please write them in the comments and we will be sure to answer them.
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Author: Ms.Geneva
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