Gardening requires a lot of effort, and when we finally start to see the fruits of our labor, we often encounter unexpected challenges. The biggest problems tend to arise in early spring and during hot summer days when fluctuating temperatures, alternating sunny and rainy periods, create ideal conditions for fungal diseases to develop on plants.
One of the most challenging plant diseases to combat is downy mildew, which frequently affects fruit-bearing plants, especially those that are particularly sensitive to this disease. A common scenario is that just as the first cucumber harvest begins, signs of infection such as yellow spots, dots, and even drying leaves start to appear. While the best approach is to use natural preventive treatments, some remedies can also help slow the spread of the disease after its onset.
Today’s topic focuses on maintaining the health of cucumber stems. When it comes to vegetable nutrition, we often emphasize the importance of nitrogen, phosphorus, and potassium. However, the significance of microelements—especially iodine—is frequently overlooked. Iodine plays a crucial role in plant protection, pest control, and disease prevention while also boosting plant immunity.
Beyond its role in strengthening plants, iodine is also used for soil disinfection. A deficiency in iodine can lead to poor fruit setting, flower rot, delayed flowering and fruiting phases, reduced fruit size, weakened immunity, and increased vulnerability to nematodes, larvae, and various fungi. Additionally, a lack of iodine affects fruit quality, reducing starch content and altering the taste of the produce.
Iodine is commonly used as a fertilizer and as a preventive measure against diseases such as downy mildew, powdery mildew, and rot. It is effective both in preventing infections and in treating the early signs of disease. Iodine applications can be done through watering or foliar spraying. Many garden and ornamental plants benefit from iodine as a fertilizer.
Among the plants most sensitive to iodine deficiency are potatoes, tomatoes, zucchini, eggplants, turnips, cucumbers, onions, cabbage, corn, leafy greens, garden strawberries, raspberries, sunflowers, and various ornamental flowering plants. However, iodine should always be applied in microdoses, as excessive concentrations can burn the plants. When using iodine for foliar feeding or plant treatment, the plants should already be mature and strong to avoid potential damage.
For seedlings, iodine should only be applied once they are well-rooted, as certain species—especially eggplants—are highly sensitive to it. This treatment should not be used frequently. One of the simplest preparations for plant protection and fertilization involves dissolving three drops of iodine in 10 liters of water. Each cucumber, tomato, eggplant, and pepper plant should be watered with one liter of this solution after planting or seed sprouting. This prevents the development of various fungi in the soil, as the spores that cause downy mildew reside in the soil and attack plants under favorable conditions. This explains why the disease typically appears first on the lower leaves of plants.
A significant concern in greenhouses and protected areas is seedling lodging, a disease that also affects outdoor plants under the right conditions. Seedling lodging is caused by pathogenic fungi from the Phytium genus, which includes over 100 different species that attack nearly every cultivated plant. These fungi live in the soil and their pathogenicity depends on factors such as moisture, temperature, light, and pH levels. Ironically, the optimal conditions we create to ensure plant growth in greenhouses also promote fungal activity. This means that better growing conditions for plants can also enhance the conditions for fungi that cause lodging. Infected plants become weak, fall over, and stop growing.
To prevent seedling lodging and other fungal diseases, all plants should be watered with the iodine solution upon planting. A specific preparation for cucumbers includes adding 1 liter of milk and 12 drops of iodine to 9 liters of water. Spraying this solution on cucumber plants and the surrounding soil helps eliminate downy mildew spores, prevent chlorosis, and reduce the risk of powdery mildew. The treatment should be repeated weekly until the symptoms disappear.
Iodine is an essential element for plant health. Without sufficient iodine, plants mature more slowly and become prone to rotting. Aside from its role in fertilization, iodine is also used in orchards and vineyards as an insecticide, preventing fungal, bacterial, and viral infections. Irrigating plants with iodine enhances immunity, regulates water flow and nitrogen exchange in plant tissues, optimizes oxygen absorption, and improves photosynthesis efficiency. Due to its strong disinfecting properties, only pharmaceutical-grade 5% iodine solution should be used.
Young seedlings should be watered with iodine only after they are planted in their final location and have grown strong enough. Spraying should ideally be done in the evening when plants have cooled down to avoid damage. Proper maintenance of cucumber stems is also crucial—pruning the stems, ensuring plant airiness, and removing lower leaves that touch the ground will help plants dry faster after rain or dew, reducing disease development and pest infestations.
For additional protection against insects, iodine can be used effectively in combination with milk. A solution of 10 liters of water and 10 drops of iodine is useful against aphids, which can spread rapidly among fruit and berry crops. By adding 1 liter of milk to 9 liters of water, and then incorporating 10 drops of iodine, an effective insecticidal spray is created. This mixture should be generously applied to trees and shrubs at the first sign of pest infestation.
To control ant infestations, the soil around their shelters should be irrigated with iodine dissolved in water at a ratio of 10 drops per 5 liters of water. However, caution is necessary when using iodine-based preparations. Exceeding the recommended doses, overapplying treatments, or using iodine in combination with additional iodine-rich fertilizers can have harmful effects, including plant burns and destruction of beneficial soil bacteria. It is crucial to follow proper ratios, even though iodine is a natural remedy—too much can be detrimental.
We hope that today’s advice comes at the right time and helps you protect and restore your plants should any issues arise. For more gardening tips and solutions, visit our channel to learn about promoting abundant flowering and increasing fruit yields in cucumbers. By using iodine wisely, gardeners can effectively combat plant diseases and pests, ensuring a healthier and more productive garden.
