Fungicides Essential to Carrot Production Worldwide

Organisms that cause diseases on carrot foliage are present wherever carrots are grown. Research has demonstrated that using fungicides to control these foliar pathogens increases carrot yields by 4-8 tons/acre.

“Alternaria leaf blight (ALB) of carrot and cercospora leaf spot (CLS) contribute to significant and recurrent losses for the production of carrots worldwide. … Foliar pathogens defoliate carrots by infecting and blighting leaflets and petioles, which in turn limits photosynthesis and energy storage in roots. Several field studies have shown 20%-80% yield loss for unsprayed carrots compared with carrots subjected to a standard calendar fungicide program.”

“In addition to yield loss, deterioration of petiole and leaf health may reduce the commercial harvestability of roots since strong, healthy petioles are required to properly lift and remove carrots from the soil. When foliage is weakened by disease, additional crop losses ensue as unharvested roots are left behind in the field. … Repeated fungicide applications are expensive but necessary on susceptible carrot cultivars to maintain crop yield and value.” 

Authors: P.M. Rogers and W.R. Stevenson
Affiliation: Department of Plant Pathology, University of Wisconsin-Madison
Title: Integration of host resistance, disease monitoring, and reduced funigicide practices for the management of two foliar diseases of carrot.
Publication: Canadian Journal of Plant Pathology. 2006. 28:401-410.

China #1 Producer of Garlic Thanks to Fungicides

China is by far the leading producer of garlic in the world, annually growing approximately 10.5 billion kilograms. Chinese garlic accounts for over 77% of world production. Following devastating outbreaks of leaf blight, research was conducted to determine the most effective means of controlling the disease.

“From autumn 2004 to spring 2008, leaf blight was found on garlic leaves in Dangyang County, Hubei, China, with the crop area affected estimated to be over 7000 ha. Garlic yield was reduced by 30% on average, with up to 70% yield losses in some fields during the winter growing season.”

“Epidemiology, cultivar resistance, and chemical controls were investigated during the 2006 to 2008 growing seasons in Dangyang County to improve disease control methods. … Relatively few of the commonly grown cultivars had high levels of resistance to leaf blight. … Fungicide applications in the field were effective in controlling leaf blight… As well, once symptoms are observed, field applications of the fungicides flusilazole (± famoxadone) or mancozeb are recommended to further combat disease.”

Authors: Lu Zheng¹, Rujing LV¹, Junbin Huang¹, Daohong Jiang¹, Xuhong Liu², Tom Hsiang³
Affiliation: ¹ Huazong Agricultural University, Wuhan, Hubei, China; ² Plant Protection Station, Dangyang County, Hubei, China; ³ University of Guelph, Guelph, Ontario, Canada
Title: Integrated control of garlic leaf blight caused by Stemphylium solani in China.
Publication: Canadian Journal of Plant Pathology. 2010. 32(2):135-145.