10 Garden Diseases to Identify and Treat

Powdery mildew is a fungal infection that is pretty easy to identify. You'll see a telltale white dusty coating on the stems, leaves, and flowers. Powdery mildew can affect various plants, including apples, cucumbers, grapes, roses, and lilac.

You can prevent this fungal infection by ensuring your plants have good drainage and by watering mid-morning so the leaves have time to dry before nighttime.

One of the worst diseases for tomato plants is a fungal infection called tomato blight. It spreads through airborne spores and flourishes in warm, wet conditions. The signs of tomato blight usually appear in the same order.

• First, small brown marks appear on the plant's lower leaves.
• The leaves will then turn pale green and yellow before falling off.
• Then, the fungus will move into the stem and branches of the plant, causing brown spots.
• The fruit will develop deep brown spots, and the branches will soften and collapse.

Tomato blight can kill a tomato plant in as little as a week, so identifying the signs early is essential.

This fungal disease can affect many plants, including trees, shrubs, fruits, and vegetables. The pathogen that causes verticillium wilt can live in the soil for years. As the fungus makes its way into the roots and then the plant's vascular system, it will wilt suddenly. The symptoms vary depending on the plant and climate, but you might see wilting in small branches, stunted growth, premature leaf loss, and yellowing leaves.

Remove and destroy any infected plants and sterilize all your gardening and cutting tools after they contact any infected plants.

Fusarium wilt is caused by a soil-borne fungus that can spread through contaminated equipment, transplants, infected seeds, or splashing water. It affects various edible and ornamental plants, like asparagus, beans, peas, sweet potatoes, and legumes. Symptoms include stunted growth, wilted leaves, stem rot, and root rot.

There's no way to cure fusarium wilt. If it takes root in your garden, remove and destroy any infected plants and wait at least five years until you replant in that soil.

Another fungal infection to look out for is anthracnose. It usually appears after a cool, wet spring and affects dogwood trees and shade trees like ash, maple, and sycamore. Look for irregular, dark blotches on the leaves, small twigs, or buds. Infected leaves usually fall off.

While this infection usually doesn't kill the tree, it does leave it looking rather unsightly. To keep it under control, prune dense areas of the tree to support good air circulation and fertilize them to help their leaves grow back.

Downy mildew is common in cooler, humid climates. You can identify it by the bluish, violet, gray, or white fluffy patches of mildew on the undersides of the leaves in damp weather. The tops of the affected leaves develop yellow, brown, or pale green areas, and they often wither and die early.

There's no treatment for downy mildew, but there are some things you can do to try to avoid it. Avoid over-watering and overcrowding, and make sure your garden has good drainage. Remove and destroy diseased plants to prevent spreading.

Another fungal disease that can affect your garden is rust. It's generally easy to spot; look for rusty spots on leaves and stems. In time, these spots progress to reddish-orange and then black. Rust can attack a variety of plants, from roses to hollyhocks to tomatoes to your lawn.

Fungicides are available, but it's a good idea to remove and destroy any infected plants.

Phytophthora root rot mainly affects ornamental trees and shrubs when they're in wet soil for long periods. Plants with this disease will look drought-stressed because their roots are damaged, and they aren't getting the moisture they need, even though the soil might be wet. Leaves will look dull and wilt, changing to yellow or red.

This disease won't kill the plant immediately, but the organism that causes it stays in the soil for years if it stays moist. Help keep it from taking hold by improving drainage, avoiding over-watering, and raising planting sites to prevent standing water.

Also called gray mold, botrytis blight affects ornamental shrubs, trees, and some garden perennials. It usually appears after a long period of rain in warm weather because the fungus that causes it likes humidity. Affected flowers will wilt and have spotting or discoloration; leaves will have brown patches and gray spores. Leaves may drop, and fruit will rot.

Treatment involves cleaning up and properly disposing of any affected plant parts, which contain the spores.

Many edible or ornamental plants can develop bacterial leaf spot. This noticeable disease may appear on the top or bottom of the leaves and look like lesions with black edges, brown spots ringed with yellow halos, or just dark or light areas. When these spots form clusters, they can kill large sections of plant tissue. This disease can also appear on the edges of the leaves; when it does, the leaves become delicate and papery.

These bacteria thrive in cool, wet conditions and can spread quickly. Rotating crops and avoiding over-watering can help prevent spread.