Study On Fungicide Seed-treatment Control Yellow Stunt And Root Rot(Embellisia Astragali) Of Astragalus Adsurgens

Yellow stunt and root rot of milk-vetch(Astragalus adsurgens Pall.) caused by Embellisia astragali is a destructive and systematic disease. Its pathogen resides within various tissues of the plant causing pasture decline, loss of forage yield and seed yield, and poor forage quality. In order to control the occurrence and damage of the disease with chemical methods, a series of experiments were carried out in laboratory greenhouse and field. The results are as follows:1. During the experiment of fungicide screening in the laboratory, the5fungicides all restrained colony growth, conidia germination, and growth of hypha of the fungus. EC50from low to high was chlorothalonil, metalaxyl, mancozeb, Thiophanate-methyl and triadimefon, in which is the best its EC50was0.028,0.03and0.04g·L-1for colony growth, conidia germination, and growth of hypha. EC50of triadimefon was0.46,0.48and0.21g·L-1. Fungicide dose effected seed germination. The safe dose was2g active ingredient per1kg milk-vetch seed for chlorothalonil and mancozeb, and3g for metalaxyl and Thiophanate-methyl.2. With all tested fungicides treament the plant seed in the greenhouse, disease incidence decreased22.28%—68.06%, disease index on aboveground and root decreased37.58—58.89and37.5—57. Plant height and root lengh increased2.3%—25%and25.5%—33.5%, biomass on aboveground and root increased17.4%—67.8%and63.6%—72.4%. Mancozeb and metalaxyl played a the most effective role in controling the disase, the control efficiency was85.5%and74.1%.3. In field experiment, with all tested fungicides treament the plant seed, disease incidence decreased1.26%—3.76%. Mortality of plant decreased1.53%—2.7%. Density of plant increased11.18%—31.58%, plant height increased2.95%—17.78%, dry weight of per plant increased3.28%—43.79%, hay yield increased3.28%—43.79%.