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Onion is an herbaceous biennial in the family Liliaceae grown for its comestible electric-light bulb . A flattened magnetic disk forms the plant ’s stem , and the tubular leaves overlap their sheath to work a pseudostem . Three to eight leaves are present per plant , either tumid or devious . The incandescent lamp comprises several layers , each gibe to a leaf . They are generally oval , but their shape can be variable and occur in clusters of 3 to 18 to a industrial plant .
The bulb is protected by a tissue layer that turn into a composition coat . In accession to red and purple Allium cepa , eschalot , and spring onion plant , onions can also be referred to by cultivars . There is no conclusive evidence of the onion ’s stemma , but it is likely to be in South East Asia , where the cistron pool is the most divers . To make better yield with gamey caliber , keep an eye on the below - listed pest and diseases and their control methods .
How to control pests and diseases in Onion crop
A typical feature of the grownup is their elongated shape , greyish to yellow - brownish colouring material , and fringed wing . Usually , eggs are hidden in the tissue paper of foliage , petals , and stubble of crops . A larva of 0.5 mm is almost see-through - white or yellowish to orange - yellow . A second - phase larva measure about 1 millimeter in length . The prepupal and pupal stages can be found in the soil ’s upper stratum and on leaf , flowers , and other shelter . Their offstage bud can identify Prepupa and pupa .
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It is one of many fly known as “ root maggots , ” but it is the only one restricted to onions and Alliums . The adults of all mintage are small , greyish - brown flies that are difficult to distinguish from one another . The onion maggot is one of the largest root maggot , about 1/4 in foresighted and slightly smaller than a theatre fly . A distinctive maggot larva is creamy - colored , stretch , and pointed at the head destruction . Only microscopic characteristics can distinguish onion maggot larvae from other species .
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The cardinal spider mite typically completes a life cycle from eggs to adult in about a week . All stage of this soupcon are present throughout the year . replication is most probable to occur when the weather is hot and wry . egg are spherical , shiny , and straw - colored and hatching within three days . Single orchis are laid on the undersurface of leave or attach to silken webs spun by adults . Three twosome of legs are on the larvae , slightly larger than the nut .
The sprightliness cycle comprise the egg , the larva , two nymphal stages ( protonymph and deutonymph ) , and the adult . The egg incubation period is 2 - 4 days ; Eggs are bind to fine silk webbing and hachure after approximately three days . Protonymphal and deutonymphal periods are 2 to 3 days each . Adult mites survive about eight solar day . The adult female can lay several hundred nut during her life — a life cycle of 7 to 9 days . The temperature determines how long it takes for eggs to become adults .
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Diseases in onion farming
The fungi that induce dull - off are usually common in an onion plant production field of study . These fungi generally exist for long full stop in soil and may persist in plant debris or on the roots of weed . The disease is more prevalent during Kharif or rainy seasons and make about 60 - 75 % impairment . Damping - off tends to be most severe under high soil wet and crunch conditions .
contagion with royal splodge is triggered by Alternaria porri , a fungus that can infect the entire reason surface and the electric light . Onions , garlic , and other allium crops are attacked by it . spore are produced at night and released in the morning as humidity decreases and are spread by breaking wind or splashing rainfall to levelheaded plant to initiate transmission .
Warm and moist environmental conditions privilege the pathogen . As a consequence , the pathogen overwinters in crop rest on or near the filth surface . The disease symptoms look 1 - 4 years after contagion , and new lesions produce black spore within five Clarence Shepard Day Jr. .
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Spray anyone of the below listed fungicide at 10 - 15 days intervals from 30 days after transplantation or once the disease appear .
Stemphylium leaf blight ( SLB ) , cause by Stemphylium vesicarium , is a foliar disease of onion worldwide . The disease stimulate small , tan to brown leaf lesions , speedily progressing to defoliate works . Crop release occurs through a reduction in the photosynthetic field , causing smaller and decreased quality of bulbs and , indirectly , hapless ledge and storage living .
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castrate anyone of the below - list fungicides at 10 - 15 days time interval from 30 days after transplanting or once the disease symptoms come along
Allium cepa anthracnose , also known as onion plant smudge , is a world-wide terror . Three unlike Colletotrichum species make the disease . Anthracnose can taint dried musical scale , bulbs , and foliage of onion plant plants . Lesions develop on the medulla oblongata , and leaves become very distorted and greensick . This disease can be manage with protectant fungicides and sound ethnical practices .
Black cast is in the first place a postharvest condition . It occurs in onions and garlic but is more of a vexation in onion plant crops . black-market mold come most commonly when onions or ail are grown under strong conditions . For the disease to develop on the bulb , moisture must be present for six to twelve hours . During storage or when bulbs fall out of repositing , capsule can cumulate between the outer dry scales of electric light . It is a weak pathogen that generally does not affect bulb that are not damage by dilapidate organic topic .
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Carbendazim 50 WP . Bitertanol 10 WP , Hexaconozole 5 EC , Mancozeb 75 WP , Captan 50 WP , Zineb 75 WP
bulb rot of onion has majuscule destructive potentiality to cause substantial economic losses to onion yield due to foliage hurt and bulb decay in the field and during reposition . These diseases are primarily a problem with onions . Water is all-important for the entry and spread of bacteria . Bacteria enter the bulb through wounds and dying lower leave . The pathogens are soilborne and may extend through irrigation water or splashing piss from rainfall or irrigation . These pathogens are prefer by warm temperatures ( over 29.5 ° vitamin C ) and wet condition .
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Conclusion
onion plant are prone to several different disease , especially in slopped growing season . These often get started on their leaves and , if stark , can reduce bulb growth and take . Therefore , if you design to cultivate onions , have a good knowledge of symptoms due to the above - hash out pests and diseases and their control methods .
