What is alternaria leaf blight of carrot? How to get rid of alternaria leaf blight? But first, let’s find out about carrot alternaria leaf blight symptoms and treatment control guidelines!
Carrot Alternaria Leaf Blight Definition
Carrot alternaria leaf blight meaning – What is alternaria leaf blight of carrot?
Alternaria leaf blight is one of the most important diseases affecting carrots leaves. It can happen anywhere in the world. Severe epidemics reduce the size and yield of carrot roots, and more crops are lost when machines can’t pull diseased or weak leaves off the plants, leaving the roots in the ground. Unfortunately, in Europe, where the weather is usually cool, serious epidemics only happen when it rains more than usual.
Carrot Alternaria Leaf Blight Causes
What causes carrot alternaria leaf blight? What is the most common cause of carrot alternaria leaf blight?
Alternaria dauci is what causes Alternaria leaf blight. The spores of A. dauci are brown and look like clubs. The main conidial body is 50–100 12–24 μm long and has one or more longitudinal and 7–11 transverse septa per segment. Each spore has a very long, split, hyaline or pale brown apical beak that measures 50–250 x 2–5μm.
Carrot Alternaria Leaf Blight Symptoms
Signs and symptoms of carrot alternaria leaf blight – What are some symptoms of carrot alternaria leaf blight?
The first sign spotted is that are greenish-brown and wet. These spots turn dark brown to black and sometimes have a yellow halo around them. Older leaflets often have spots on or near the edge. When there are a lot of spots on a leaf, the whole leaf turns brown and yellow. As the spots get bigger and stick together, the leaf might die. Crops severely damaged have large areas where the leaves look burned or blighted. On the petioles, dark, rectangular, long lesions show up. The pathogen also hurts carrot seed plants’ flowers, bracts, and developing seeds. Alternaria leaf blight symptoms may look like those of other leaf diseases of carrots, such as bacterial leaf blight and Cercospora leaf blight. To tell these different leaf blights apart, you must look at them under a microscope and test them in a lab.
Carrot seedlings can die if they get sick soon after sprouting, which can happen if the inoculum comes from the seeds or the soil. The upper roots of affected seedlings turn gray or black near the soil, similar to what Pythium species do. But there aren’t many reports of infected carrot roots in carrots that have been picked and stored. A. petroselini, A. smyrnii, and A. selini are all celery and parsley pathogens belonging to the Apiaceae family.
Carrot Alternaria Leaf Blight Disease Cycle
Spores can start to grow on wet leaves in two hours and spread disease through the stomata. Sporulation and infection can happen at temperatures between 8 and 30º C, but 25º C is the best. The disease cycle takes only 8 to 10 days from infection to sporulation. This means that epidemics can spread quickly. The pathogen is carried by the seeds and can be found in the mericarp and on the surface of the seeds. It can live for a few years on seeds and a few months on dead plants. Infested crop residues may be an important source of inoculum, especially if carrots are grown year after year. When crops are grown next to each other in order, the wind can carry inocula from the older crop to the newer crop.
Carrot Alternaria Leaf Blight Treatment Guidelines
Treatment of carrot alternaria leaf blight – What is the best treatment for carrot alternaria leaf blight?
Use seed that doesn’t have a lot of the disease-causing agent. Treat carrot seeds with hot water or fungicides if there aren’t many infections that can spread from seed to plant. The effectiveness of dicarboximide seed treatments has decreased since fungicide-resistant strains were developed. Because different carrot cultivars are more or less likely to get sick, choose ones that are more resistant or tolerant. Rotating carrots with non-hosts can cut down on soil-borne diseases. Don’t put newer carrot fields next to older fields that might have diseases. Check carrot crops often for signs of Alternaria leaf blight and use fungicides when needed.
In Canada, a way to deal with Alternaria leaf blight based on predictions has been made. This system uses the length of time that a leaf is wet and the temperature to figure out infection indices. These numbers show how likely an infection will be mild, moderate, or severe. For example, severe infection is likely if the leaves are wet for more than 72 hours at 7º C or more than 12 hours at 16º–20º C. Before using infection indices, they will need to be checked to make sure they work in the area. In addition, gibberellic acid has been used to make the leaves of carrots grow faster. It may also be a way to treat Alternaria leaf blight.
I hope you understand carrot alternaria leaf blight symptoms and treatment control guidelines.