tailieunhanh - Báo cáo nghiên cứu nông nghiệp " Management of Phytophthora Diseases in Vietnamese Horticulture 2 ( end)"

Tham khảo luận văn - đề án 'báo cáo nghiên cứu nông nghiệp " management of phytophthora diseases in vietnamese horticulture 2 ( end)"', luận văn - báo cáo phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Two General Categories of Epidemics Depend on the Disease Cycle of the Pathogen Disease Assessment One cycle of pathogen reproduction per crop cycle Disease progress curve linear or flat Ex. Fusarium or Vcrticillium wilts ninny wil-bomc pathogens Several cycles of pathogen reproduction per crop cycle Disease progress curve sigmoid Ex. Potato late blight. wheat stem rust many airborne pathogens Disease assessment measurement of the amount of disease on a plant crop field orchard over space and through time is necessary for Crop loss assessment predict how much yield loss is due to different amounts of disease Disease survey how much disease is present in different areas Disease Assessment Two basic principle of disease management derived from epidemiology Incidence The proportion or percentage of diseased plants within a sample unit. Example The number of infected plants in a field Severity The area of plant tissue that is diseased usually relative to the total area. Example The percentage of leaf area infected In a field. 1. Monocyclic diseases are most efficiently suppressed by reducing the amount or effectiveness of primary inoculum. Example use clean seed or crop rotation to reduce primary inoculum. 2. Polycyclic diseases are most efficiently suppressed by eliminating large amount of primary inoculum and or by limiting potentially rapid rates of disease increase. Example use resistant varieties or fungicides Usually goal is not 10 prevent epidemic but to delay its progress sufficiently to allow crop to mature and produce economical yield. Epiikniìtílogy ÚỈ p. palmivtíra More disease Less disease Table Field scale or potato late blight Pflyfophttoa irrHĩstanữ 1 Percentage description combines incidence ano seventy Keys and Scales Can Measure Different Parameters No disease Observed. nfy a rew scattered plants arretted not moretnan 1 tf ZSfMtsin 12-yd radus Up to 10 spots per plant or general slight spotting About 50 spots per plant up to 1 in 10 leaflets in .

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