![]() ![]() Follow this with regular and consistent field monitoring, starting at the seedling stage and continue until harvest. Monitoring and Disease ForecastingĪs part of an integrated crop management program, the first key ingredient for successful celery blight management is control of the disease in the seedbed. The disease is spread by water splashes, farm machinery and field workers especially when the foliage is wet. Bacterial blight is favoured by cool, wet conditions and at least 10 hours of leaf wetness is required for infection. The disease survives on infected seed and on plants left in the field over winter. Bacterial leaf blight of celery rarely infects the petioles.įigure 5: Septoria late blight on celery petioleįigure 6: Severe Septoria infection on celeryįigure 7: Bacterial leaf blight of celeryīacterial blight is easily distinguished from early blight and late blight because the lesions do not have pycnidia, like late blight or spores, like early blight in the lesions. As the spots increase in number they merge to eventually kill the leaf tissue. As these enlarge with a yellow halo, they turn to a rust colour (See Figure 7). ![]() The initial symptoms appear on the leaves as small, bright yellow, circular spots. It is very important to stay out of celery fields infected with late blight when the foliage is wet.īacterial leaf blight of celery is not as common and is caused by the bacteria Pseudomonas syringae pv apii. Once in the field, the disease can be spread by water splashes, farm machinery, animals and field workers. If environmental conditions are favourable, field infections are far worse when infected seedlings are planted. It is very important to monitor the emerged seedlings throughout the greenhouse to ensure that no leaf blight symptoms are developing. Septoria late blight comes primarily from infected seed and remains viable in seed for up to 2 years. Late blight also affects the petioles of celery and can become quite severe if the plants are growing slowly and there are heavy dews at night. ![]() Spores of Septoria apiicola are dispersed over a much shorter distance (several meters) than those of Cercospora apii (many meters). Spores come from these pycnidia and are dispersed by rain splash or wind-driven rain. This can be seen with the naked eye and looks like small flecks of pepper or muck soil in the center of the spots. (See Figure 3) Septoria blight is also characterized by having small, black, flask-shaped bodies called pycnidia embedded within the lesions. These spots quickly turn dark brown to black and several small lesions may join to form a larger spot. Septoria late blight is caused by the fungus Septoria apiicola and initially develops as small, reddish-brown spots on older outer leaves. The disease can be spread readily by wind, water splashes, field workers and farm machinery. Early blight is favoured by high humidity and temperatures between 15☌ and 30☌. The fungus is both seed-borne and soil-borne and can survive in infected plant residues in the soil. (See Figure 2)Ĭercospora may also infect the celery petioles when disease pressure is high.Ĭercospora usually appears earlier than Septoria late blight, however this is not always observed. (See Figure 1) Leaves with many spots will eventually dry up, wither and die. These spots rapidly enlarge up to 1 cm or more and turn dry and brown. Biology and SymptomsĬercospora early blight is caused by the fungus Cercospora apii and is initially characterized by small, round, tan spots on the leaves. Management of celery leaf blights depends upon regular and consistent field monitoring, weather monitoring, cultural controls, field selection, variety selection and properly timed fungicide applications at threshold levels. In the future, forecasting models may improve the management of these diseases by providing early warning of disease infection periods. Although these diseases may not affect overall yield every year, symptoms on leaves and petioles can add considerable time and effort to harvesting and trimming operations.Ĭelery leaf blights need to be correctly identified early in the infection cycle for control measures to be successful. It is incited by Pseudomonas syringae pv apii. Bacterial leaf blight may also appear during wet growing seasons or later in the season when the crop gets larger. Cercospora early blight and Septoria late blight often weaken the leaves and petioles of celery and reduce the marketability of the crop. Two fungal leaf diseases commonly affect celery in temperate North America. ![]()
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