Common Plant Diseases:
Introduction to Common Plant Diseases:- Well, to become a successful farmer, you should be aware of common garden plant diseases and pests or crop diseases. Knowing symptoms and providing appropriate control measures in any garden or orchard is one of the primary tasks in agriculture and horticulture sectors. Not only the yield but also quality will be impacted by these plant diseases and insect pests. You must be aware of symptoms and causes of these plant pests and diseases to treat them on your own. Never experiment with sprays and dusts without know the exact disease or pest. At the same time, using too much of insecticides or pesticides are dangerous to environment and soil. There are natural ways of controlling pests and diseases. Most of the plant diseases and pests reflect their symptoms. Plants diseases are grouped into fungal, viral or bacterial diseases. In the following article let us discuss types of plant diseases commonly attack the vegetable plants, fruit plants, other agriculture, and horticulture crops.
Main Types of Plant Diseases:
Common Plant Diseases – Blights:
Causes of Blight: Plant Blight diseases caused by a pathogenic organism (bacteria or fungus).
Symptoms of Blight: Leaves and Branche’s withering, spotting, browning, yellowing and ultimately results in plant death. Blight can also show the symptoms of discoloring of stems, fruits, and leaves.
Types of Blight Diseases: Fire Blight, Early Blight (Alternaria Blight), Late Blight and Bacterial Blight.
Blights Affected Plants: Both Indoor and Outdoor plants are susceptible to blight disease. Most of the ornamental plants, most of the vegetable plants, most of the fruit trees, and shade trees.
- Select quality seeds which are free from all kinds of diseases and disease resistant cultivars.
- If the crop is grown from cuttings, they should be from healthy mother plants.
- Maintain proper space and light conditions
- Soil or growing medium pH should be maintained at an optimum level.
- Avoid water logging and water stress all the times. You should provide balanced irrigation depending soil moisture status.
- Remove any pests from the orchard or garden as these pests may encourage the growth of pathogens that cause blights.
- Remove all the affected areas of the plant with the help of pruners.
- Avoid composting or fertilizing the infected parts of the crop.
- Blight disease may be due to bacterial or fungal infection. Based on this antibiotics or fungicides should be used to treat the affected plants.
Common Plant Diseases – Cankers:
Causes of Cankers: This is a fungal disease that mostly attacks bark of woody plants, lower hidden areas, small areas of dead tissue and in cracks or wounds of the tree. The canker disease mainly caused by biotic fungi and bacteria or extreme temperature conditions. Improper panting, hail, high winds, root rot, insect borers may also cause the canker disease.
Types of Cankers: Cytospora Canker and Nectria Canker.
Symptoms of Cankers: The symptoms are circular, discolored areas on the bark of the trees.
Cankers Affected Plants: Most of the trees and shrubs. Some of the affected pants are Spruce, pine, poplars and willows, juniper, Russian olive, Douglas-fir, and arborvitae, honey locust, oak, and maple.
Control Measures of Cankers:
- Disease resistant cultivars should be used.
- Cut off the affected branches or limbs with proper pruning methods.
- Avoid any injury to roots and trunk as wounds are the main cause of spreading canker disease.
- Grow only trees and shrubs that are adapted to the area and choose vigorous planting material and plant in a good location. Apply manures and fertilize on time to promote healthy growth.
- Control the weeds by taking appropriate intercultural operation.
- Limiting pruning of wounds may also prevent this kind of disease.
- Avoid cutting into trunk cankers as it may renew fungal activity. No effective chemical controls are available to prevent or control the fungi that cause this disease.
Common Plant Diseases – Rusts:
Causes of Rust Disease: Rusts are nothing but fungal diseases ((pathogenic fungi) that can cause colored powder on leaves. Generally, rusts require a living host to complete their life cycle.
Types of Rust Diseases: Asparagus Rust, other type rusts include white pine blister rust, wheat rust, and cedar-apple rust.
Symptoms of Rust Disease: Rust disease is mainly seen in mid to late summer and autumn.
- Rusts make pale leaf spots and they finally end up into spore-producing structures which are being called as “pustules”.
- The pale leaf spots are found on the lower side of the leaf.
- Rust disease stop the growth of the plant by killing the vigor.
- These pale spots are yellow, brown, black, white even orange color.
- Rusts cause the leaves to shred prematurely.
- Apart from leaves, Pustules can also be formed on stalks, stems.
Rust Disease Affected Plants: Most of the garden plants.
Control Measure of Rust Disease:
- Apply neem oil to prevent rust by killing spores on the plant leaves.
- Maintain enough space between plants for better aeration.
- Plant disease resistant cultivars.
- Remove diseases and dead leaves from the plants.
- Don’t apply too much of nitrogen fertilizers.
- which can cause high vegetation which can encourage this rust disease.
Common Plant Diseases – Wilts:
Causes of Wilt Disease: Generally, plants/trees/shrubs get wilt in case of water stress. Permanent wilting is caused by fungi when it attacks plant’s water conduct system. Wilt disease affects the vascular system of plants. Mostly the symptoms of wilt are same as blights.
Types of Wilts: Stewart’s Wilt, Verticillium Wilt, and Fusarium Wilt.
Symptoms of Wilt Disease: The affected plants with wilt may turn yellow and ultimately die.
Wilt Affected Plants: Both Indoor and Outdoor plants are affected. Most of the flower plants, vegetable plants, fruit plants, and ornamental plants.
Control Measures of Wilt Disease:
- Select wilt disease-resistant varieties of plants or seeds.
- Don’t plant again in the same place where wilt problems have occurred.
- Crop rotation is advisable.
- Try to eliminate flea beetles.
- Cut off affected branches and plants and destroy them.
Common Plant Diseases – Rots:
Causes of Rot Disease: Rot disease can make your plants by causing decay of roots, stems, wood, flowers, and fruits. The main cause of rot disease is overwatering and poor drainage. Indoor plants are more susceptible to the rots when compared to outdoor plants.
Types of Rots: Root rots, Stem rots, Fruit rots, Mushroom rots, and Wood Rots.
Symptoms of Rots: Poor growth, Wilted, yellowed, or browned leaves, pale leaves, roots decay and thinning of the plant canopy.
Rots Disease Affected Plants: The indoor and outdoor plants both are affected by rots disease. It is more common in indoor plants with poor drainage.
Control Measures of Rots:
- Avoid poor-drainage soils and plant new trees in raised beds for well-drainage.
- Avoid too much of water and ensure to avoid water logging especially in rainy season.
- Water only when needed especially drought and soil dry conditions.
- Remove all the affected plants immediately before spreading to other planting areas.
- Chemical application of methyl bromide in and around the base of the infected trees may reduce the level of the infection but it does not cure completely.
Common Plant Diseases – Other Types of Diseases:
Common Plant Diseases – Anthracnose:
Causes of Anthracnose Disease: This disease mainly caused by fungi in the genus of “Colletotrichum” which is a common group of plant pathogens that are responsible for diseases on many plants of gardening.
Symptoms of Anthracnose Disease: This disease infected plants/trees/shrubs develop dark, water-soaked lesions on stems, leaves, and fruits.
- Avoid composting infected leaves of plant, fruits, and stems. You should prevent fungal spores.
- You can start spraying liquid copper sprays and sulfur powders when foliage begins to develop in the early spring and continuing throughout the growing season.
- You can spray neem oil, which can kill eggs, larvae and fungal attack on plants. This is the best method of organic pest control.
Common Plant Diseases – Scabs:
Scabs are caused by fungal infections which can attack plant leaves, fruits, and tubers. This disease can cause hardened, overgrown, and cracked tissue. Fruit scab is a serious problem in apples and pear fruits.
As part of control measures, timely pruning activities should be carried for better airflow and proper planting space should be maintained. Remove any infectious and fallen leaves from the site. Sulfur fungicide can be sprayed to control the scabs.
Common Plant Diseases – Smuts:
Common Plant Diseases – Leaf Spots:
Leaf spot disease is caused by fungi. Usually, this disease attacks plant leaves. A leaf spot disease can progress to a blight or blotch disease. When it comes to color, a leaf spot could be a brown or black depending on the type of fungus. You can also observe concentric rings or dark margins around the spot.
The symptoms of this include yellowing of leaves which can eventually drop prematurely.
To control the leaf spot disease, you can follow these activities.
- Spray fungicides which can change the pH balance of the plant.
- Make sure the soil has well-drainage around the plant.
- Add organic materials through composting which can result in beneficial microorganism activity.
- Prune or remove all the leaf spot infected leaves or branches throughout the season and once again before winter.
- Never make the plant leaves wet which can encourage the leaf spot disease.
Common Plant Diseases – Nematodes:
The symptoms of Nematodes include the reduced growth of the plant. Apart from this, this disease can also cause wilting of the plant. Some other symptoms may include root attacks such as rotted roots and enlarged lumps on roots. Nematodes affect the vegetable and ornamental crops. To control Nematodes, soil organic matter should be maintained properly. Always choose disease-resistant varieties of seed or seedlings. Never carry the affected soil to other plants. Growing cover crops like marigold can reduce the Nematodes problem. Solarizing soil can also help in reducing Nematodes population. You can also follow crop rotation to prevent this problem.
Common Plant Diseases – Powdery Mildew:
This disease is caused by fungus and powdery mildew disease can leach nutrients from the plant which can result in the leaves to wither and become yellowish. This is a most widespread disease in garden plants. Usually, mildew forms a white powdery growth on the upper surfaces of plant leaves. Sometimes, it could be a greyish powder. Infected fruits with Powdery mildew disease can result in premature ripening and have poor texture. To control this disease, follow these activities in your garden.
- Maintain enough space between plants while sowing or planting.
- Ensure proper light conditions and avoid shady location.
- Sulfur fungicide can be applied to plants even before appearing this disease.
- Remove dead and diseases plants on a frequent basis.
- Don’t over fertilize your garden plants or crops or orchards.
- Destroy infected plants along with proper pruning activities for better air flow.
- Spraying “Bicarbonate” can prevent the powdery mildew disease.
Common Plant Diseases – Club Root:
- Symptoms: The infected plants are wilt during the day and leaves become yellow and can drop off. This disease mainly attacks vegetables and flowers in the cabbage family.
- Causes : This disease mainly caused by fungal infection.
- Control measures: Select disease-resistant varieties and If you’ve had past club root problems in the garden or field, avoid replanting the crop. However, you can also adjust soil pH.
Common Plant Diseases – Black spot:
Black spot disease is a frequent disease that can attack rose plants. The spots appear on the leaves and are around 1 to 1.25 cm along with yellowish margins. Seriously affected plants shred the leaves. In order to control this disease, use disease resistant cultivars, and remove the infected leaves. Spray Bicarbonate which can prevent leaf spot diseases. This disease generally caused by a fungus.
To control black spot disease, always keep the plant leaves dry as wet conditions encourage black spot disease and make sure there is good drainage around the plant base. You can also spray fungicides like sulfur or copper to change the pH balance of the plant for creating a healthy environment. Keep adding organic material through composting.
Common Plant Diseases – Leaf Blisters and Curls:
Leaf blister and leaf curl are fungal infections that cause jagged, curled leaves on many trees. Peach leaf curl disease attacks peaches and almonds. Oak leaf blister can defoliate and also kill pine trees. Blisters are yellowish bumps on the top surface of these leaves, with grey depressions on the lower surfaces. You can spray appropriate fungicide just before budding for controlling this disease.
Common Plant Diseases – Damping-Off:
- Symptoms of Damping-off Disease: You can observe sudden death plants.
- Causes of Damping-off: This disease is caused by fungal infection. Damping-off can infect sprouts right at the soil line. If the seedling is dying without any warning you should suspect this disease.
- Control Measures of Damping-off: Use soil-less seedling mix, not potting soil, for planting seeds and for planting cuttings. Keep the mixture moist, but not soggy. Sprinkle a little peat moss or corn meal around the bottom of seedlings to absorb extra water, where the fungi breed is expected.
Common Plant Diseases – Viral Diseases:
Most viral diseases are incurable. Seasonal crops and short duration plants such as Banana and Papaya afflicted with viral infections. Aphids are main causes of several viral diseases. By controlling aphids, viral infections may be avoided to some degree. Some of the viral diseases include Bunchy top of Banana, leaf curl of Tomato and brinjal, Chilli and Papaya, the yellow mosaic foliage of okra.
Common Plant Diseases – Downy Mildew:
Causes of Down Mildew: The fungi are the main cause of this disease.
Symptoms of Down Mildew: The main symptom of this disease appear as upper leaf surfaces have a pale color and downy growth, usually on the undersides of leaves of the plants. This can also appear along stems, which turns black with age.
Affected Plants with Down Mildew: fruit crops, vegetable crops, flower crops, and grasses are affected by Down mildew disease.
- Buy only quality disease-resistant seeds and plants.
- Crop rotation practices must be followed to prevent this disease.
- Infected branches/stems/trees should be destroyed.
- You can use preventive chemical sprays.
Common Plant Diseases – Crown Gall or Galls:
Causes of Crown Gall Disease: Galls are nothing but swollen tissues of the plant. This disease may be caused by fungi or bacteria or insect pest.
Symptoms of Crown Gall Disease: The disease symptoms include roundish rough-surfaced galls (swollen surface of tissues) at or near the soil line, on a graft site or bud union, or on roots and plant lower stems. The galls usually are at first cream-colored and later turn brown or black. Eventually affected plants lose vigor and die.
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Affected Plants of Crown Gall Disease: Grapes, members of the rose family, shade and nut trees, most of shrubs and vines, and perennial garden plants including some vegetables.
Control Measure of Crown Gall Disease:
- Avoid buying unhealthy plants and seeds.
- Avoid nursery planting material with suspicious bumps near the crown.
- Protect the plants from injury.
- If the field is affected by crown gall disease, don’t replant in the same field for couple years.
- Destroy Gall effected plants/stems.
- Disinfect any tools used to prune the Gall affected plants before using them on other plants or trees.
- Maintain weed-free field throughout the lifecycle of garden plants.
Common Plant Diseases – Nutrient Deficiencies in Plants:
Common Plant Diseases – Nitrogen Deficiency (N):
- Symptom of Nitrogen Deficiency: Leaves of the plants start turning into a yellowish color. This starts from the lower part of the plant and eventually all leaves become yellow or pale.
- Cause of Nitrogen Deficiency: Nitrogen is very important nutrient required by most of the plants in your garden. You should supply adequate ‘N’ for healthy leaf growth.
- Control Measures: You should feed the garden plants with compost and fertilizers having good amounts of Nitrogen. You can feed this nutrient until the leaf canopy reaches the full-size. For better absorption of nitrogen, you can add an amino-acid supplement to your nutrient solution.
Common Plant Diseases – Phosphorus Deficiency (P):
- Symptom of Phosphorus Deficiency: This can cause slow-growing plants to drop the leaves very frequently drop and plant leaves (Foliage) may be tinted with dark green, purple or blue.
- Cause of Phosphorus Deficiency: Phosphorus is a key nutrient that plays a major role in growing plant roots and converting sunlight into energy. Phosphorus Deficiency plants will have very slow growth and leaves lack the green colour.
- Control Measures for Phosphorus Deficiency: Adding bone-meal can boost the Phosphorus nutrient in your garden.
Common Plant Diseases – Potassium Deficiency (K):
- Symptom of Potassium Deficiency: Indoor plants can have weak blooming. It can cause scorched tips along with limp branches.
- Cause of Potassium Deficiency: Potassium is a key nutrient which is essential for plant reproduction. Potassium deficiency in plants can look at first like light stress. However, the weak stems and limbs shows up for more Potassium (K). tell you that your plants need more K.
- Control Measures for Potassium Deficiency: As plants grow the need for potassium nutrient increases, especially in flowering plants. Your plants in the garden requires more input of ‘K’ in flowering season when compared to ‘N’. If you are growing flowers on commercial scale especially in greenhouse/polyhouse or even hydroponically, ensure the flowering plants are supplied adequate Potassium.
Note: Without knowing the symptoms or diagnosing the plant diseases, don’t experiment with sprays and fertilizers or chemicals. The local department of Agriculture and Horticulture are best sources for finding the common plant diseases and their symptoms.