Spots on your leaves may indicate a fungus has invaded. Immediate action is called for to save your plants. Fungus is usually caused by overwatering or high humidity. When fungus invades your garden, avoid watering in the evening until the problem is eliminated.
There are various types of fungus that may attack your garden. Most are plant family specific. We'll cover Powdery Mildew, Blossom End-Rot and Blight in the tabs below.
Powdery mildew looks like powdery splotches of white or gray, on the leaves and stems of plants. It can also affect the buds, flowers and fruits. The mildew spores are carried to your plants by wind, insects and water. Powdery mildew can also be caused by Aphids.
Conditions that encourage the growth and spread of powdery mildew include:
• Dampness or high humidity
• Poor air circulation
• Crowded planting
What can you do about it once you're plants have it? A few homemade solutions can quickly take care of this problem.
Fungicidial Milk spray
Spraying diluted milk on cucumbers and other squash family plants such as eggplant kills powdery mildew.
Dilute liquid dish detergent or other insecticidal soap with water until it is a 1 or 2 percent solution and then spray on plants.
Blossom End Rot
Blossom End Rot occurs when the ripening fruits starts to develop a dark, watery spot on the bottom of tomatoes, squash, or zucchini. The decay spreads quickly and eventually leaves the bottom of the tomato sunken and scabbed over.
Blossom End Rot is a calcium deficiency. This can be caused by a number of things:
Uneven watering. Make sure to water regularly and uniformly. If using an irrigation method like a soaker hose, check the system for clogs. During periods of drought or intense heat you will need to increase watering frequency. Or, if has been sitting in cold, wet soil, you may be overwatering or the soil is not draining properly. Planting a tomato too early in the spring can also make it susceptible to blossom end rot as well. Check your seed packets carefully before planting.
Soil Deficiencies. Two types of soil deficiencies contribute to Blossom End Rot: Lime and phosphorus.
Your soil may not have enough lime and therefore not enough calcium. The only way to know this is to get your soil tested. An easy way to add calcium directly to the plant is to add a handful of bone meal to the planting hole when you plant. You can also add Dolimite Lime to the soil after planting. It is available at nurseries or hardware centers. Spread on the soil around the plant.
Your soil my not have enough phosphorus. You will need to increase the phosphorus content in your fertilizer for plant uptake. Tomatoes need a fertilizer that is high in phosphorus - this is the middle number you see on the fertilizer box (NPK ratio). The middle number should be higher than the other numbers. Most fertilizers labeled specifically for tomato use will have a higher phosphorus content.
Shallow root systems. In order for the plants to take up the calcium and nutrients it needs through its roots, the plant needs to be rooted in deep, well-drained soil. Planting other plants too close can also interfere with the root system.
Sometimes, the whole plant is doomed. But if caught early enough, you may be able to save the whole plant. Pick fruits that are showing signs of the disease - usually the lowest fruits will show signs first - and toss it. The fruit cannot be saved at this point. The rest of the plant will likely recover and the other fruits will not affected.
Blight is caused by a fungal infection. There are several varieties of blight that will affect mostly tomatoes and potatoes, but also other plants in your home garden as well. These are Septoria blight, Early blight and Late blight.
Septoria blight Appearing at the end of July with small brown or black marks, it is the least harmful to plants. Most fruits will remain unaffected unless significant leaf loss occurs. Try watering at the base and avoid wetting the leaves and stems.
Early blight The most disappointing blight is the Early blight. Onset occurs at heavy fruiting. Brown and black spots appear on the leaves first, then the stems. Soon after the fruit begins to develop large bruises and fall off the stems. If early blight attacks your crops, remove affected plantsas soon as it is discovered and burn all affected plants to keep next years crops from being affected.
Late blight is the most devastating disease for potato and tomato growers worldwide because it spreads rapidly and is usually fatal to the infected plant and even complete crops if left unattended. It attacks in rainy weather with cool nights and quickly infects fruits.
On tomatoes, late blight usually begins as pale green, soft spots, often starting at the leaf tips or edges. The irregular shaped spots are lined with a pale yellowish-green border. The lesions will grow rapidly and the center will become a very dark color. Stems will turn brown or black and may die off quickly if wet conditions are present. In wet conditions the leaf will form a white mold on the surface of the lesions. In hot weather, the leaf usually dries up, and mold disappears. Late blight can also appear on the fruit as a large, firm, brown spots and, if conditions are moist, will also develop mold.
On potatoes, late blight shows as a shallow, coppery-brown dry rot that is about 1/8 - 1/2" deep. On the surface of the tuber, the irregular spots will appear brown, dry and sunken.
Prevention is the only real solution to blight treatments. Most fungi grow best in warm, dark, wet climates. Avoid these by:
1. Watering only the ground surrounding the plants - be sure to avoid getting leaves and stems wet.
2. Allow enough drying time if watering in the evening to prevent water from sitting overnight.
3. Avoid walking in the garden while wet to prevent spores from traveling in splashing water.
4. Completely remove garden debris from tomatoes and potatoes, especially if infected.
If using a fungicide as the prevention method, apply as directed early in the season. To ensure maximum efficiency, you will most likely need to apply regularly throughout the season.
Prevention is the key to ensuring a blight-free crop but if your plants become susceptible there are a few remedies you can try.
If caught early, a good remedy is an application of fungicide obtained from your gardening center and applied as directed.
Or, if it's only one plant, sacrificing that plant for the betterment of the crop is a quick fix. Immediately, and carefully, pull it up to stop the spreading of the fungus. If it is on several plants, remove all the pieces of the plant infected. Be sure not to drop any pieces in the garden. Dispose of the plant or plant pieces far away from the garden and wash your hands and clothes in warm soapy water. You may also want to carefully infuse the soil with calcium (powdered milk or crushed eggs shells) around the remaining plants.
After an attack from blight, the blight may remain in the soil. Cold weather will kill it but it will take at least one season. Plant the crop in a different location the following year.