Just like humans, plants also suffer from a plethora of diseases which can completely disrupt their natural functioning and can cause a variety of ailments to these precious green creatures ranging from slight discoloration to drooping leaves to even death of the plant. Diseases have many causes including fungi, bacteria, viruses, and nematodes.
Below are 10 of the most common diseases affecting plants:
- Blight:
Blight, any of various plant diseases whose symptoms include sudden and severe yellowing, browning, spotting, withering, or dying of leaves, flowers, fruit, stems, or the entire plant. Most blights are caused by bacterial or fungal infestations, which usually attack the shoots and other young, rapidly growing tissues of a plant. Fungal and bacterial blights are most apt to occur under cool moist conditions, and most economically important plants are susceptible to one or more blights, including tomatoes, potatoes, and apples, as well as many ornamental species.
2). Canker:
A ‘canker’ is really a symptom of an injury often associated with an open wound that has become infected by a fungal or bacterial pathogen. Canker diseases frequently kill branches or structurally weaken a plant until the infected area breaks free, often in a wind or ice storm. Bacterial canker is most common on cherries and plums, but may also affect apricots, peaches and many other kinds of stone fruits. Suspect this plant disease if sunken, water-soaked or “gummy” lesions form on the trunk or twigs.
3. Gall
Galls are abnormal growths that occur on leaves, twigs, roots, or flowers of many plants. Most galls are caused by irritation and/or stimulation of plant cells due to feeding or egg-laying by insects such as aphids, midges, wasps, or mites. In general, galls provide a home for the insect, where it can feed, lay eggs, and develop. Each type of gall-producer is specific to a particular kind of plant.Galls may appear as balls, knobs, lumps, or warts, each being characteristic of the causal organism. In addition to the unusual structure of galls, they draw attention due to their range of colors: red, green, yellow, or black.
4. Leaf Curl
A fungal disease that affects peaches and nectarines, leaf curl (Taphrina deformans) is one of the most common disease problems found in backyard orchards. Symptoms appear in spring as reddish areas on developing leaves. These areas become thick and puckered causing leaves to curl and distort. When severe, leaf curl can substantially reduce fruit production. Leaf curl is most active at temperatures between 50-70˚F, but can occur at relatively low temperatures. In fact, cool weather is thought to extend the infection period because new leaves are growing slowly. Wet weather is necessary for infection.
5. Leaf Spot
Leaf spot diseases, particularly those of vegetables such as tomato, pepper and lettuce are of two types, those caused by bacteria and those caused by fungus. Leaf spotting of either kind is generally similar in appearance and effect. Infected plants have brown or black water-soaked spots on the foliage, sometimes with a yellow halo, usually uniform in size. The spots enlarge and will run together under wet conditions. Under dry conditions the spots have a speckled appearance. As spots become more numerous, entire leaves may yellow, wither and drop.
6. Powdery Mildew:
Common in many plants and easily recognized, powdery mildew is a fungal disease which is caused by a variety of closely related fungal species, each with a limited host range. (The fungi attacking your roses are unlikely to spread to your lilacs). Low soil moisture combined with high humidity levels at the plant surface favors this disease. Symptoms usually appear later in the growing season on outdoor plants. Powdery mildew starts on young leaves as raised blister-like areas that cause leaves to curl, exposing the lower leaf surface. Infected leaves become covered with a white to gray powdery growth, usually on the upper surface; unopened flower buds may be white with mildew and may never open. Leaves of severely infected plants turn brown and drop. The disease prefers young, succulent growth; mature leaves are usually not affected.
7. Root Rot
Sometimes if a plant is overwatered, it just doesn’t seem to recover afterwards. The leaves start to get dull and turn yellow, and the whole plant seems to be on a slippery slope towards death. You try to correct the watering issue but nothing seems to help. Chances are, your plant is suffering from root rot. Root rot can have two sources — one is a prolonged exposure to overwatered conditions that can cause some of the roots to die back due to a lack of oxygen. The other source can be from a fungus in the soil. The fungus may lie dormant in soil indefinitely and then suddenly flourish when the plant is overwatered once or twice. The root rot fungus attacks the roots and causes them to die and rot away.
8. Wilt
On a hot, dry day (or after several days with no rain or watering), transpiration causes more water to be lost than is coming in, and the water balance within the plant can get thrown off. The dehydrated collapsing cells in the leaves and stems can no longer remain erect, and the plant begins to wilt. Interestingly, wilting also serves to reduce water loss, as the drooping leaves expose less surface area to the sun’s evaporative rays. Most plants recover quickly when given water, though prolonged dehydration can be fatal or cause leaf death.
9. Stunt:
Stunt, in agriculture, is a common symptom of plant disease, resulting in reduced size and loss of vigour. Stunting may be caused by viral, bacterial, fungal, or nematode (eelworm) infections and by noninfectious (abiotic) means including an excess or lack of water, imbalance of soil nutrients, excess light, chemical or mechanical injuries, insect or mite feeding, and too-deep planting. A stunt caused by an infection is often too far advanced to remedy when it is discovered; an abiotic stunt, however, can usually be remedied.
10. Chlorosis
Chlorosis is a symptom of plant disease in which normally green tissue is pale, yellow, or bleached. It results from failure of chlorophyll to develop because of infection by a virus; lack of an essential mineral or oxygen; injury from alkali, fertilizer, air pollution, or cold; insect, mite, or nematode feeding; gas main leaks; compaction or change in soil level; and stem or root rot. Severely chlorotic plants are stunted, and shoots may die back to the roots. Enzymes secreted by microorganisms play a key role in disease development. These break down plant substances into smaller molecules which pathogens easily absorb and utilize for its growth and energy.
William Henry Gates III is an American business magnate, investor, author, philanthropist, and humanitarian. He is best known as the principal founder of Microsoft Corporation.
