Presentation on diseases of cotton plants

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  1. 1. WEL-COME
  2. 2. An Assignment on Disease of Cotton Plants Submitted by: Santosh pathak IAAS, Lamjung Campus ( AG )
  3. 3. Introduction : Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. Cotton is the king of fibres, usually referred as white gold . Current estimates for world production are about 25 million tones annually, accounting for 2.5% of the worlds arable land. China is the worlds largest producer of cotton, but most of this is used domestically
  4. 4. The United States has been the largest exporter for many years. Cotton is grown mainly for its fibre used in manufacture of cloth for the mankind. It is also used for several other purposes like making threads, for mixing in other fibres and extraction of oil from the cotton seed. Cotton seed after extraction of oil is a good manure and contains about 6% nitrogen, 3% phosphorous and 2% potash. Cotton seed, cotton linter and pulp obtained during oil extraction and cotton meal are good concentrated feed for cattle. Contd.
  5. 5. cultivated cottons are annuals. Cultivated cotton is a herbaceous plant which attains a height of 60 to 200cm. The plant has a tap root with secondary roots that branch laterally from primary root. The main stem is erect and much branched; the branches develop from buds located at the nodes of the main stem. The leaves are spirally arranged on the main stem. Cotton belongs to the malvaceae family and the genus Gossypium. The genus Gossypium has been one of the most difficult to classify. Genus Gossypium includes 50 species in which 46 are wild and 4 are cultivated. According to classification by Hutchison (1947) the following four cultivated species contain almost all the varieties of cotton in case of India. Gossypium arboreum Gossypium herbaceum Gossypium hirsutum Gossypium barbadense
  6. 6. Objectives: To be familiar with the diseases found in the cotton. To be able to know the sign and symptoms of disease. To get maximum ideas regarding the control measures and management of disease found in cotton. To be familiar about the pesticides like fungicides, insecticides and their use in the crop at different times applying different methods
  7. 7. Review of literature Cotton crop is attacked by a number of diseases. Symptoms of important diseases and their suitable control measures are given below. Seedling diseases: Seedling diseases are presently causing great losses to cotton producers in Tennessee. They comprise the number one disease problem. The estimated loss is an average of 9.72 percent annually based on a range of 5 to 18 percent since 1989. Loss estimates do not include cost of replanting or losses due to lateness of replanted cotton. CAUSE . The organisms include both seed and soil-borne fungi and bacteria. The soil-borne fungi, Rhizoctonia solani and Pythium spp., are the most important causes of seedling diseases in Tennessee. Rhizoctonia solani is the fungus most commonly associated with seedling diseases; however, during cool, wet seasons Pythium spp. may become more prevalent.
  8. 8. SYMPTOMS The various phases of seedling diseases include seed-rot, root-rot, pre emergence damping-off, and post emergence damping-off. Root-rot (or black-root) may occur anytime. Pre emergence damping-off refers to the disease condition in which the seedling is killed between germination and emergence from the soil. The death of seedlings resulting shortly after their emergence from the soil is termed post emergence damping-off. The latter is referred to as "sore shin" when only stem girdling occurs. Rhizoctonia is usually the cause of sore shin. CONTROL Fungicides seed treatment helps control seed rot and some pre emergence damping off. Some of the practices include use of correct planting equipments and date of planting, good Contd..
  9. 9. Root rot This disease is caused by soil-borne fungi Rhizoctonia bataticola and Rhizoctonia solani . The diseased plants occur in more or less circular areas and this is very characteristics of the disease. The affected plants can be easily pulled out of the ground. The roots of the affected plants decay and a yellowish brown discoloration sets in. In badly affected plants the wood becomes brown or thick. Due to this disease perfectly healthy plants may wilt within 24 hrs with leaves dropping without showing any discolouration. Control measures: Irrigate frequently to keep down soil temperature. Follow a wheat-jowar-paddy-cotton rotation. Treat the seed with Brassicol(75w.p.) 200g/50 kg of seed of acid delinted seed and 300g/ 50 kg of machine delinted seed.
  10. 10. Fusarium wilt This disease is caused by a soil-borne fungus Fusarium moniliform, Fusarium vasifectum. Plants can be affected this disease in any stage. Disease incidence in seedlings can be high in cold soils, but mean temperatures about 230c favors the disease . In young as well as old plants the initial symptoms are stunting followed by yellowing, wilting and dropping of most of the leaves. The cut stems of wilted plants shows brown or black vascular tissues inside. In old plants, lower leaves towards the base are affected first followed by younger ones towards tips. Leaf discoloration appears around the edges and progresses towards the midrib and leaves gradually drop.
  11. 11. Control measures: .Grow tolerant varieties like LD-694. Application of potash and organic matter in sufficient amount is helpful in reducing disease. Soak 4 kg seed(non-delinted) in 8 litres of water containing 8 g of Bavistin/Derosal for 6-8 hrs and 2-3 hrs in case of delinted. Avoiding over irrigation and over application of nitrogen.. Crop rotation Field inspection for early detection and containment of isolated outbreaks. Farm hygiene.
  12. 12. Verticillium wilt: . Verticillium wilt is caused by the soil-borne fungus, Verticillium albo-atrum. This fungus can survive in the soil for many years even in the absence of cotton. Cotton seedlings infected with Verticillium usually turn yellow, dry out, and die. Plants which become infected later in the season are stunted and exhibit a yellow condition along the leaf margins and between the major veins. This yellow imparts a mottled appearance to the plant. Severely affected plants will shed their leaves. Sprouts or new shoots may develop near the base of infected plants. The discoloration associated with Verticillium wilt is usually more evenly distributed across the stem than that associated with Fusarium wilt. The browning of the stem tissues are also usually less intense where the wilt is caused by Verticillium. Control by using Deltpine and crop rotation.
  13. 13. Boll rot: Boll rots have caused heavy losses to cotton producers during wet growing seasons. Rain and high humidity during late summer and fall are optimum conditions for boll-rot development and increase the incidence of the disease. A number of fungi and bacteria have been associated with boll rots. Some of these organisms invade the cotton bolls directly, whereas others enter through insect wounds or as secondary invaders. Infected seed will result in seedling blights the following season. Boll rots usually first appear as water-soaked spots. Later, as the infection spreads, the bolls turn black and may be covered with a moldy fungus growth. Badly infected bolls may drop from the plant. Control measures: To prevent boll rots, cotton growers should avoid excessive applications of nitrogen which promotes rank growth of cotton. It has been found that skip-row cotton provides better air drainage, resulting in less boll rot. Defoliation will also help reduce boll rots.
  14. 14. Angular leaf Spot (Xantomonas malvacearum): It is also known as Bacterial blight. This disease is usually least severe in or absent in hot dry condition, but it can be severe during warm wet weather. It is quite sever in the irrigation cotton growing area of the country. Symptoms will be most severe on leaves when the humidity is high with air temperature average 86-95 degrees F and when rain, heavy dew, fog or sprinkle irrigation are frequent. Small round spot occur in the cotyledon during the early seedling stage of growth and angular lesions on the older plants. The disease on the leaves appears first as water soaked spot that enlarge to angular brown to black lesion. The spot occurs on the leaves from the seedling to the mature plants stage during of high temperature. The spot are light-green spots that are visible on the upper and lower surface of the leaves. These spots quickly turn dark brown to black . The margin of this spots has sharp angles. The round, light green lesions on bolls may develop into boll rot. Black elongation lesion occurs on the young stem.
  15. 15. Control measure: The acid delinted seed should be treated with 0.1% Streptocycline solution, by keeping it emmersed for 2hrs (Two grams of streptocycline dissolved in 20 liters of water is enough to treat seed required for one acre).It should be dried on the shade and the seed should be treated with Ceresin wet or Agrosan. G.N@25- 10 kg of the seed .If seed is not acid delinted it should be treated with Streptocycline as described and after coating it with slurry of ash and dung it should be treated with Ceresan or Agrosan G.N. The crop should be sprayed from the time of the first appreance of the disease with Blitox 50, flytolan, Blue copper 50 or Cupramer in a concentration of 0.3 to 0.5 % considering the severity of the disease. Resistance variety should be used. Rotating cotton with soybean or corn planting for once or more years will help reduce the severity of bacterial blight on next cotton crop. Plant only acid-delinted seed produced in fields free from this disease. Contd
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