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Abstract:
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duced losses determined from symptom-affected patches were 21-29% for herbage and 15-25% for seed. In a grazing experiment with swards of cvv. Denamrk and Leura at a third site, BYMV-induced overall herbage yield decreases of 8-12% were still recorded despite extensive BYMV spread to control swards; yield losses within symptom-affected patches were 18-25% for herbage and 35-47% for seed. Seed yield losses were due to decreased seed size (mean seed weight), fewer seeds being produced, or both. Estimates
lso as regards depletion of the seed bank, which, when compounded year by year, results in pasture deterioration. Early and prolonged aphid activity, reseeding the pasture with susceptible cultivars, heavy grazing and extended growing seasons are all l
nding infected patches. Later, secondary patches, isolatd affected plants and more generalised infection sometimes developed. The extent of spread within swards from the transplants varied with cultivar, BYMV isolate, site and year. Final BYMV incide 9.
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