LEAF SPOTS AND BLIGHTS Several leaf spot and blight diseases occur on cotton and under favorable conditions can cause considerable damage. The most important of these diseases are Ascochyta blight (wet weather blight), bacterial blight (blackarm and angular leaf spot), Cercospora leaf spot, and Alternaria leaf spot.
Cotton crop suffers from several diseases but the increasing pattern of target leaf spots, TSV, boll rots, bacterial leaf blight, alternaria leaf spot, and grey mildew, is observed and may become an emerging threat to cotton cultivation.
Boll weevil (Anthonomus grandis) and pink bollworm (Pectinophora gossypiella) are serious cotton pests. For much of the 20th century, they caused tens of millions of dollars in damage to cotton producers, reduced land values, and greatly disrupted local economies.
Downy Mildew
This is the most common crop disease. Downy Mildew is different from powdery mildew, so it is important to know the difference. Powdery mildew is a fungus that causes a white powdery substance to appear on the upper leaves.
Rust of cotton is an aggressive disease caused by the fungus Phakopsora gossypii. It is not seed- or soil-borne and thus needs green living tissue to survive. During the season, the spores produced in the pustules of cotton infect gramma grasses (Bouteloua spp.)
'Cotton wool disease' is a general term applied to the most common fungal infections that infect the skin, fins, and mouth. The fluffy white growths often colonize areas where there have been previous infections, parasites, or injuries. The most common types of fungi in these infections are Saprolegnia and Achyla.
Rust Identification/Symptoms: Rust diseases go through different stages, but they all eventually form blister-like, powdery pustules. The pustules typically occur on the undersides of leaves, but stems and upper leaf surfaces can develop pustules, too.
White blister is a plant disease that affects brassica crops and is caused by the fungus-like organism Albugo candida. There's no risk to consumers, as the fungus only affects the growth and appearance of brassica plants.
Numerous bacterial diseases affect crop production in many countries and regions. These include fire blight in fruit trees, bacterial wilt in banana, bacterial blight in rice and crown gall in many perennial plants.
However, sometimes thrips, plant bug, cotton aphid, bollworm, stink bug, or spider mite feeding can result in significant yield losses.
Bad boll opening is also called as Tirak. The problem is basically concerned with premature and improper cracking of bolls, instead of normal fluffy opening (Fig 8). Initially the leaves turn yellow and subsequently become red. The capsule wall of the bolls become tight and do not open completely.
Pink bollworms damage squares and bolls, the damage to bolls being the most serious. Larvae burrow into bolls, through the lint, to feed on seeds. As the larva burrows within a boll, lint is cut and stained, resulting in severe quality loss.
The root rot caused by Rhizoctonia bataticola (Taub) Butler and Rhizoctonia solani Kuhn is one of the most seroius diseases of cotton particularly in the northern region of India where around 1.8 m. hectare area exists in the states of Punjab, Haryana, Rajasthan, western Uttar Pradesh and Jammu and Kashmir.
This red colour is caused by a dye which is secreted by the host and is antagonistic to the red rot fungus. Infection takes place through mother setts, holes in the nodal regions, the cut ends of the seed canes and other injuries.
Bluetongue is a non-contagious, viral disease spread by biting insects. It affects species of ruminants, particularly sheep. Bluetongue causes many different symptoms in affected animals, including ulcers, sores, painful hooves, lameness and reproductive problems.
Without treatment, leptospirosis in people can lead to kidney damage, meningitis (inflammation of the membrane around the brain and spinal cord), liver failure, trouble breathing, and even death. About 1 million cases in people occur around the world each year, with nearly 60,000 deaths.
The cotton aphid is a vector for more than 50 plant viruses including potato virus, citrus tristeza virus, cucumber mosaic virus, and turnip mosaic virus (2–4). The host range for the cotton aphid includes more than 50 plant families including Asteraceae, Cucurbitaceae, Rosaceae, and Solanaceae (5–7).
Black stem rust is an important disease of wheat. It also affects oats, barley, rye, timothy grass, and wild grasses. Black stem rust is caused by the fungus Puccinia graminis—an organism that must alternate between two host plants (a cereal grain and barberry) to complete its lifecycle.
White rust of mustard is caused by the fungal pathogen Albugo candida, is one of the most common and economically harmful diseases in mustard farming. The disease typically affects the leaves, stems, and pods, leading to visible symptoms that can significantly reduce crop yield if not managed properly.
Fighting rust fungi with home remedies
This tried-and-tested treatment is simple to make at home. Simply mix 1 teaspoon of baking soda with 1 litre of water, then thoroughly spray affected and vulnerable plants. Repeat the application every couple of weeks to maintain control over rust fungus.
Most cankers are caused by fungi, which invade bark tissue on current season wood. However, some colonize both bark and inner tissue causing cankers that persist for years. All fungal cankers contain fruiting bodies that appear as pinhead-sized, black or colored raised bumps embedded in the bark.
For most of the year cedar-apple rust is hard to see. However, when spring rains moisten the hard brown kidney-shaped galls that over winter on cedar trees they develop bright orange spore horns. These are very conspicuous and make the cedar look like it's fruiting.