Using crop canopy modification to manage plant diseases
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Using crop canopy modification to manage plant diseases Mary Ruth McDonald & Bruce D. Gossen & Cezarina Kora & Monica Parker & Greg Boland
Accepted: 19 November 2012 / Published online: 17 January 2013 # UK Crown Copyright 2013
Abstract Modifying crop canopies can suppress plant diseases in some crops. For example, in carrot, lateral trimming of the canopy by 30–40 % after canopy closure reduced sclerotinia rot (Sclerotinia sclerotiorum) to zero under moderate disease pressure without the use of fungicides. Trimming reduced relative humidity within the carrot canopy and increased air and soil temperature, inhibiting the formation of apothecia of S. sclerotiorum. Trimming also severed infected petioles, which reduced the opportunity for infection to progress to the carrot crown. Trimming combined with application of foliar fungicide was even more effective. Trimming reduced carrot leaf blights (Alternaria dauci, Cercospora carotae) in 1 of 3 years, when disease pressure was low. However, there was no advantage of combining trimming and fungicide sprays for leaf blight control. Canopy modification also reduces disease in legume crops. Soybean cultivars with reduced height and lodging, and early maturity, had up to a 74 % reduction in apothecia of S. sclerotiorum within the crop, and up to an 88 % reduction in disease M. R. McDonald (*) : M. Parker : G. Boland University of Guelph, Guelph, Ontario, Canada e-mail: [email protected] B. D. Gossen Agriculture and Agri-Food Canada, Saskatoon, Saskatchewan, Canada C. Kora Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada
incidence at harvest. In field pea, artificially supporting plants to reduce lodging, in combination with fungicide application, reduced the severity of mycosphaerella blight (Mycosphaerella pinodes) on pods by 67 % and increased seed yield by 54 %. In chickpea, paired-row planting that opened the canopy increased seed yield by 12 %, likely by increasing fungicide deposition. Modifications of the crop canopy can reduce disease, the need for fungicide sprays, and sometimes improve fungicide efficacy, but the results are often pathosystem-specific. Keywords Carrot . Field pea . Chick pea . Soybean . Carrot trimmer . Sclerotinia sclerotiorum . Ascochyta pinodes
Modifications to plant canopies to suppress disease can be achieved through a variety of approaches. Various degrees and types of canopy modification, including genetic, mechanical, and cultural, have been studied and adopted for disease management in many crops. Mechanical modification of plant canopies to reduce disease is routinely used in the production of only a few high-value crops, such as pruning of grapes to manage botrytis bunch rot (R’Houma and Boubakker 1998) and pruning coffee to reduce the severity of coffee rust (Arneson 2000). In field crops, plant genotypes with upright and compact growth habits offer important options for architecturally-based disease avoidance mechanisms. Modifying plant canopies through breeding and cultural approaches is used across a range of crop type
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