Celery anthracnose: a newly identified fungal disease of celery
Cultural practices and a rotation of strobilurin and protectant fungicides can limit celery anthracnose, a damaging disease of celery.
An anthracnose fungus has been identified as the cause of unusual symptoms occurring between 2010 and 2012 in Michigan celery. Below are some questions and answers about the biology and control of this disease from Michigan State University Extension.
What is celery anthracnose?
Celery anthracnose is caused by the fungus Colletotrichum acutatum. This specific fungus is known to infect other vegetables including pepper, tomato, and spinach. It was first reported as a pathogen on celery in Australia during the 1980s, and was first detected in Michigan in 2010. The common name of this disease is “anthracnose” and is shared with diseases of onions, tomatoes and cucurbits. However, anthracnose in these crops refers to diseases caused by other types of fungi, not the C. acutatum that infects celery.
What are its symptoms?
Symptoms include cupped leaves and twisted petioles with long and thin brown lesions (Figure 1). Other symptoms include development of adventitious roots.
Figure 1. Pictures of celery anthracnose symptoms in the field including
(A) a severely symptomatic plant next to an asymptomatic plant,
(B) young symptomatic plants, (C) leaf curling, (D) adventitious root
formation in petioles, (E) gall initiation, (F) twisted petioles with lesions
and (G) an oval lesion. Photo credit: Rodriguez-S L.M and Hausbeck M.K 2010
What are its economic impacts?
Twisted petioles make infected plants unmarketable.
How can I differentiate anthracnose symptoms from aster yellows?
Similar to anthracnose, aster yellows can cause plant twisting and curled leaves. However, foliage of plants affected by aster yellows turns yellow, while foliage of anthracnose-infected plants remains green.
What conditions favor disease?
Recent work in the Hausbeck lab – funded by Project GREEEN – showed that spread of celery anthracnose occurs at temperatures as low as 59 degrees F, but increases in periods with warmer weather or extended leaf wetness, with spores spreading via rain splash.
What cultural controls should I use?
In the greenhouse, disinfect flats prior to re-use, or use new flats each year. This sanitation practice is a mainstay of any standard disease program and is important for both foliar blights and root rots. Scout celery seedlings at least twice each week and look for disease symptoms (Figure 2). Limit periods of humidity in the greenhouse with a ventilation system and by watering seedlings at a time of day that will allow them to dry quickly.
Figure 2. Symptomatic celery seedlings in the greenhouse. (A) a flat of
celery seedlings, with symptomatic plants highlighted with a red circle,
(B) and (C) leaf cupping on plants from the circled area under magnification,
(D) lesions on celery seedling petioles. Photo credit: Rodriguez-S L.M and Hausbeck M.K 2011
In the field, during the growing season, use practices that limit spread of this disease. Irrigate at a time of day that will allow leaves to dry rapidly. As you begin field operations, work fields with a history of disease after you finish work in locations with no history of the disease. Whenever possible, avoid working fields when leaves are wet (e.g., after fog, dew, irrigation, or rainfall). If you work fields when the foliage is wet you may spread the pathogen from one location to another within a field. If possible, power-wash your equipment with a soap and water solution after working each location to remove soil and plant debris that could carry the disease-causing spores between fields (note that chlorine disinfectants can corrode steel equipment).
Are there any disease-resistant varieties?
Michigan State University researchers tested ‘Greenbay’, ‘Sabroso’ and ‘Dutchess’ varieties; all were susceptible when challenged with the anthracnose pathogen.
Can I reduce inoculum on my farm by controlling weedy hosts?
The host range of C. acutatum is so broad that there is no single weed species you can target.
What fungicides are available for the greenhouse?
To be used in the greenhouse, a fungicide label must list celery as an application site AND not prohibit greenhouse application. Unfortunately, labels of fungicides that can be used on celery in the field – including formulations of Quadris, Cabrio and Bravo – prohibit greenhouse applications. However, pre-2013 labels for Heritage (Azoxystrobin) and the current label for Catamaran (Chlorothalonil) include celery and allow greenhouse application. If possible, use these two fungicides in a rotation to control celery diseases in the greenhouse. Check your Heritage label carefully to be sure that the product you have allows the use of this fungicide on celery seedlings in the greenhouse.
What fungicides are available for the field?
Research suggests a rotation of strobilurin fungicides (e.g., Quadris or Cabrio) with protectants (e.g., Bravo or Manzate) can limit anthracnose. These fungicides will also reduce early and late blights of celery.