What are the symptoms of late blight? How to control the late blight of celery? Let’s find out about late blight celery symptoms and treatment guidelines!
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Late Blight Celery Definition
Late blight celery meaning: What is late blight celery?
Late blight is probably the most important disease of celery leaves worldwide. In the worst cases, it can wipe out an entire crop. Most problems are caused by diseases that spread through seeds, so the severity varies from season to season. This pathogen that hurts celery also hurts celeriac. For example, S. petroselini, a different species, causes septoria blight on parsley. Late blight in Apiaceae plants is not the same as late blight in tomato and potato plants, which is caused by Phytophthora infestans.
Late Blight Celery Causes
What causes late blight celery? What is the most common cause of late blight celery?
Septoria apiicola is a fungus that causes late blight. Pathogens are easy to spot because they have black pycnidia embedded in plant tissue. Pycnidia are ostiolate, have a diameter of 75–195 μm, and have hyaline, multicelled, filamentous conidia that are 22–56 x 2–2.5 mμm in size. There has been no report of a perfect stage. The pathogen comes from seeds. Celery and celeriac are not affected by the pathogen S. petroselini, which causes Septoria blight in parsley.
Late Blight Celery Symptoms
Signs and symptoms of late blight celery: What are some symptoms of late blight celery?
The first signs are small, green spots on the leaves less than 5 mm in diameter. Soon, these spots will turn brown and die. Then, they will have small, black fruiting bodies (pycnidia) on them. Some of the spots on the leaves have green edges. Most spots have an angular shape. In the field, the disease first appears on older, lower leaves. Over time, the symptoms move up to younger leaves. As the disease spreads, the number of spots on the leaves grows, the spots join together, and the whole leaf can turn brown and look blighted.
The petioles are also at risk and can get greyish-brown lesions with odd shapes full of pycnidia. Celery with diseased petioles can’t be sold, so they must be cut off before being sold. If it rains on crops or sprinklers water them, diseases can spread quickly and do a lot of damage to the crops. Since seeds spread the pathogen, they can show signs on transplants. When it’s humid, spores leak out of the pycnidia and form white, curled threads on the leaf surfaces. Celeriac has symptoms that are the same as those of celery.
Late Blight Celery Disease Cycle
Most of the time, the pathogen comes from infected seeds. The pathogen can live on seeds for 2 to 3 years if kept dry and cool (5–15º C). Under normal conditions, it looks like a seed can last about a year. S. apiicola is more likely to live in storage conditions that are good for celery seeds. Spores get into the leaf through the stomata and epidermis. In 7 to 8 days, under ideal conditions, leaf spots appear.
In the range of 5–25º C, the disease’s severity worsens as the temperature increases. The disease’s severity also increases when the time that leaves are wet goes from 72 hours to 96 hours. When leaves are wet for at least 24 hours at 20º C, the conditions are perfect for the disease to grow. Severe epidemics tend to happen when it rains for a long time or when overhead sprinklers are used all season. As the name suggests, late blight usually happens after the leaves close and as crops get close to being ready.
Late Blight Celery Treatment Guidelines
Treatment of late blight celery – What is the best treatment for late blight celery?
Use seed that doesn’t have a lot of the disease-causing agent. Before planting the seed for transplants, treat it with hot water (30 minutes at 48–49º C), aerated steam, or fungicides. A chemical treatment that works well is to soak seeds in a 0.2% thiram solution in water for 24 hours at 30º C. Store infected seeds for at least 2 years to greatly reduce the amount of viable inoculum that can spread through the seed. Then, check the transplants, and don’t use any that have signs of illness.
Don’t grow celery crops right after each other so that diseased crop residue can break down. Kill any celery or celeriac plants that grow on their own. After the transplants are set up in the field, use furrow or drip irrigation to water the crops. Don’t walk through diseased fields or drive equipment before going into healthy fields because the disease can stick to clothing and equipment. Before a plant gets sick, use fungicides as a preventive measure. Some progress has been made in using predictive models to schedule sprays, and in North America, leaves that have been wet for 12 hours or more have been used as a treatment threshold. However, resistant cultivars in commercial lines are not yet available.
I hope you understand late blight celery symptoms and treatment guidelines.