As it is with most things pertaining to your garden, active preventative methods are the best thing to use to combat plant diseases. Feeding your plants regularly with organic material, attracting beneficial insects to help stave off pests and using crop rotation are the best ways to keep your garden clean and healthy. However, sometimes it doesn’t matter how many preventative measures we use to help keep our plants disease free, and they become infected anyway. This can happen due to extreme weather or even imbalances in your soil, and the only way to help your plants is to treat the disease as it comes up.
The best way to deal with these tragic and frustrating situations is to start by identifying what you’re dealing with. Rule out insects by inspecting your plants carefully… can you see any eggs or insect waste anywhere on the leaves? Insects leave some sort of clue that they have been hanging around, so look closely, even with a magnifying glass if needed. Next you’ll need to determine whether there is some sort of environmental disruption that may be polluting your plants or the soil. Are there any sources of pollution nearby that may be contaminating your plants?
If you are able to rule out both insects and pollution, it’s time to inspect the symptoms.
Areas of discoloration or colored dots on the leaves, stems or fruit?
You may have a parasitic fungi infection. Fungi produce tiny spores that are carried by the wind, water, insects and gardeners. The spores will germinate to form mycelia, which are the body of the fungus, and the areas on your plant that can be identified as the discolored areas or dots.
Dark streaks on the leaves or stems and slime that smells bad?
These are the signs of a bacterial infection. Bacterial diseases spread easily and quickly, carried by wind, water, insects and tools alike.
Below are some more specific symptoms and diseases, along with how to prevent and eradicate them:
Leaves have dead, brown spots as well as holes and rips?
This could be a sign of parasitic nematodes. These are harder to diagnose, as the symptoms pointing to parasitic nematodes can also be symptoms of nutrition deficiency. They travel freely in water and through contact with infected garden tools. Dispose of diseased plants and use a cover crop ofmMarigolds to reduce nematode amount. Be sure to consistently keep soil rich in nutrients with applications of organic matter.
Withered leaves and branches along with rotting roots and dark, sunken spots on the fruit of the plant?
You may be dealing with blight. There are a couple different types: early, late, fire and bacterial. To prevent blight, use only disease free seed, and keep air around your plants well circulated. The best way to deal with blight is to dispose of the infected plant and rotate your crops.
Brown or black spots on fruit, eventually turning fruit soft and squishy or hard and withered depending on type?
These can be symptoms of rot, though they often are confused with symptoms of blight. Fruit, root, stem, mushroom and wood rots are the most common types. They can be caused by inadequate air flow, infected planting medium and inadequate drainage. The best way to deal with rot is to dispose of the diseased plant and avoid it’s contact with other plants. Increase air flow around crops.
Powdery tan or rust colored coating on leaves?
This is a sign of rust. Rust is carried on the air, and overwinters, so it must be eradicated by removal and burning of the plant. To prevent rust, make sure there is good air flow and that you remove diseased plants at the first signs of infection.
Plants are wilting and turning yellow, and may have bacterial ooze where stalks are broken?
These can be signs of wilt. Wilt is caused by bacteria and fungi carried on insects such as flea beetles that clog the plant’s water conducting system. The plant is starved of water and will wither and die. Destroy any infected stalks or plants. If you catch it early, remove the affected stalk well below the area of disease.
Seedlings rotting at the soil line and falling over?
This may be a case of damping-off, which is caused by soil borne fungi that thrive in too-wet soil. Keep your soil damp but not waterlogged, have good air flow and use disease-free soil starting mix to prevent damping-off.
White to purple downy growth, usually on the undersides of leaves and along stems, which turns black with age?
Sounds like a case of downy mildew. It is spread by wind, rain and infected seeds, so be sure to always plant disease-free seed. The only way it can be eradicated is to remove and destroy the infected plants. At the first signs of it, try using a bicarbonate spray to head it off.
White to grayish powdery growth, usually on the upper surfaces of leaves?
This is a sign of powdery mildew, which is one of the most common infections. Good air circulation will prevent it, and using a bicarbonate spray can assist in getting rid of it in the early stages.
Areas of hardened, overgrown, and sometimes cracked tissue on fruits, leaves or tubers?
This is a sign of scabs, which can be controlled by appropriate pruning and airflow as well as raking up and disposing of fallen leaves. It is most commonly found on peaches and apples.