| Summary: | 碩士 === 國立中興大學 === 植物病理學研究所 === 82 === A baiting technique using alachor-treated seeds of alyce clover (Alysicarpus vaginalis DC. ) provided a rapid, and sensitive means of assessing inoculum potential of damping-off pathogen of garden peas. Rhizoctonia solani AG-4, in artifically infested soil and field soils. Recovery of R. solan AG-4 from soils was best when seeds of alyce clover treated with alchor at 500 ppm for 1hr were mixed in infested soils and incubated for 48 hr at 24 C. The alachor-treated alyce clover seed colonization method was more effective to detect small population of R. solani AG-4 in soils than the multiple-pellet soil sampler method. Percentages of alachor-treated seed of alyce clover colonized by R. solani AG-4 were highly correlated (r=0.96-0.98, p<0.001) with percentages of damping-off of garden peas.
Thirteen fungicides were drenched individually to sandy loam soil artificially infested with damping-off pathogen of garden pea seedings, R. solani AG-4, for two days in the greenhouse . Benomyl, mepronil, PCNB, pencycuron, rizolex , and thylate inhibited significantly colonization of alyce clover seeds by R. solani AG-4. Seed treatment with benomyl, mepronil, pencycuron or rizol was siguificantly effective to reduce disease incidence of Rhizoctonia damping-off of garden pea seedings.l Three fungicides, mepronil, pencycuron, and rizolex drenched respectively to soil at weekly intervals for 3 times provided 60-100% of the disease control and increased root fresh weight and nodule number of garden pea seedlings. In two field trials, both seed treatment and soil drenching with mepronil, pencycuron or rizolex were significantly effective to control pre-emergence and postemergence damping -off of garden peas caused by R. solani AG-4.
Nineteen organic amendments were added (2%, w/w) individually to sandy loam soil artificially infested with R. solani AG-4, the causal agent of damping-off of garden peas. Bone-meat meal, blood meal, castor seed pomance, fish meal, forest mushroom growth medium waste, peanut seed pomance, rice husk meal, rape seed pomance and soybean pomance significantly reduced colonization of alyce clover seeds. by R. solani AG-4 . Nine organic amendments effective to inhibit the pathogen were added at each rate of 0, 0.25, 0.5, 0.75, and 1%(w/w) indiviually to artificially infested soil. Bone-meat meal, blood meal, fish meal or rape seed meal at a rate of 0.5%(w/w) was able to, markedly inhibit colonization of alyce clover seeds by R. solani AG-4 and reduce emergence percentage and growth height of garden peaseedlings. However, castor pomance, peanut seed pomance and soybean pomance at a rate of 0.5%(w/w) increased seed colonization by the pathogen. In addition, nine chemicals (amendments), were also added (0.5%,w/w)individually to artificially infested soil. NH4NO3H3PO3, Al2(SO4)3 and urea were effective to inhibit seed colonization by R. solani AG-4. A formulated amendment (FB mixture ) consisting of 20kg fish meal , 15kg bone-meat-meal, 5kg blood meal and 2kg rape-seed meal mixed with 4kg HN4NO3 was the most effective to inhibit the seed colonization by the pathogen, but it caused injury to seedlings of garden peas. Another formulated soil amendment (FBN-5A mixture) consisting of 20kg fish meal, 15kg bone-meat meal ,5kg blood meal, 2kg rape-seed meal, 4kg NH4NO3,25kg forest mushroom growth medium waste and 25L allyl alcohol (10%, v/v) added 0.75 percent by weight to soil sontrolled more than 60% of damping-off of garden pea seedlings caused by R. solani AG-4 in the greenhouse. The FBN-0.5 mixture was also applied to control damping-off of garden pea seedlings in field microplot tests. In infested soil amended streakedly at the rate of 600kg/hectacre before sowing the seeds, FBN-5A mixture was able to reduce signifcantly pre-and post-emergence damping-off of garden peas caused by R. solani by 36% and increased pea pods production compared to nonamended treatments.
Seeds of garden peas (cv. Taichung No.11) were sown in four soils infested with R. solani AG-4. Disease incidence of seedling damping-off of garden peas was more severe in soils from Chihu and Wufeng areas than from tali and Hsinshe areas . Deep planting of seeds made much more seedling tissues be infected by the pathogen Infection of basal stem and root of garden pea seedlings by the pathogen was significantly reduced by shallow planting the seeds Soilpiles were made from Tali soil and applied as the seats for sowing the seeds. Discolored length (degree) of garden pea seedlings caused by the pathogen was significantly reduced and root fresh weight of its seedlings was increased when height of soilpiles for sowing the seeds was over 3 cm from the surface of infested soil. In two field tests, soilpiles amended and nonamended singly with fish meal, bone meal and blood meal at the rate of 0.5%(w/w) were significantly effective to control damping-off of garden peas caused by R. solani AG-4 However, there was no difference in amended and nonamended soilpiles for effective control of Rhizoctonia damping-off of garden peas.
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