Impact of topography and management on diseases of canola and wheat

摘要

Severity of plant diseases on field crops can be expected to vary over a landscape in relation to topography. The objective of this study was to understand the variability of diseases of canola and wheat over a landscape, and to determine the effectof fungicide application on canola over the landscape. Field experiments were established on hummocky terrain at one site for canola and at two sites for wheat. For canola, treatments were fungicide sprayed or unsprayed, and for wheat treatments consisted of combinations of seeding rate, and N and phosphorus application. Diseases were identified, their severity determined and plots harvested for yield from areas representing upper, mid and lower slope positions within each plot. Alternaria black spot of canola increased in severity from upper to lower slope positions. Fungicide application reduced disease severity on all slope positions, however a yield increase on sprayed over unsprayed plots was detected only on the lower slope positions. Septoria and tan spot of wheat were observed to be more severe on upper as opposed to lower slope positions and common root rot was determined to be less severe on upper slope positions than on mid or lower slopes. Treatments did not have an effect on disease severity of wheat. This study indicated diseases of canola and wheat varied with terrain and that targeting of crop protectants to specific slope positions may by beneficial for disease control.