Seasonal Dynamics of Alfalfa Foliar Pathogens in Iowa

Impact and Importance of Foliar Diseases of Alfalfa in Iowa

“…Crop injury is defined as the visible or measurable symptoms and/or signs caused by plant pathogens or pests, and crop damage is defined as any reduction in the quantity and/or quality of yield that results from crop injury (Nutter et al, 1993). Plant pathology evolved into its own science not because plant pathogens cause injury, but because injury often results in loss of revenue or direct loss of a food source (damage) (Nutter et al, 1993). Injury (disease intensity) can often be measured quantitatively.…”

“…Estimates of loss are a prerequisite to the rational development of any agricultural research program that has plant protection as a component (Mumford and Norton, 1984;Nutter and Gaunt, 1996). Reliable estimates ofloss facilitate the objective identification ofthe relative importance ofbiotic pests (Nutter et al, 1993). Consequently, limited resources (federal, state, or private farmer) can be assigned on a priority basis to optimize returns from a given effort.…”

Effect of Glyphosate Application on Foliar Diseases in Glyphosate-Tolerant Alfalfa

“…Defoliation caused by foliar pathogens has been measured from 3 to 71% depending on time of year, environmental conditions, and locale (18,22). Defoliation caused by foliar pathogens has been measured from 3 to 71% depending on time of year, environmental conditions, and locale (18,22).…”

“…Defoliation caused by foliar pathogens has been measured from 3 to 71% depending on time of year, environmental conditions, and locale (18,22). Fungicide treatments are cost-effective in only some years and locations (18,22). Fungicide treatments are cost-effective in only some years and locations (18,22).…”

“…In addition to yield loss, foliar diseases can reduce seed yields and forage quality (15). The major foliar diseases of alfalfa include spring black stem and leaf spot (Phoma medicaginis), common leaf spot {Pseudopeziza medicaginis), rust (Uromyces striatus), Leptosphaerulina leaf spot (Leptosphaerulina briosiana), summer black stem and leaf spot (Cercospora medicaginis), anthracnose (Coltetottichtim trifolii), and Stemphylium leaf spot (Stemphylittm botryosum) (9,10,22,27). The major foliar diseases of alfalfa include spring black stem and leaf spot (Phoma medicaginis), common leaf spot {Pseudopeziza medicaginis), rust (Uromyces striatus), Leptosphaerulina leaf spot (Leptosphaerulina briosiana), summer black stem and leaf spot (Cercospora medicaginis), anthracnose (Coltetottichtim trifolii), and Stemphylium leaf spot (Stemphylittm botryosum) (9,10,22,27).…”