论文部分内容阅读
Understanding the biology and epidemiology is essential for developing appropriate management strategies to control canker caused by Botryosphaeria dothidea which is the most important disease that threaten the production of Chinese hickory.Ascospores were not captured throughout the study period in 2009-2012 and conidia are found to be the main source of inoculums on Chinese hickory.None conidium was observed until March 31, in 2009, 2011, 2012 and until April 7 in 2010.The late spring to early summer (May to June) is the main spore dispersal period.The number of spores trapped during May 12 to 26 May was 43.9%, 52.8%, 51.4%, 49.2% for 2009, 2010, 2011, and 2012, respectively.Through comparisons of the patterns of canker lesion multiplication and spore dispersal, we speculated that B.dothidea overwintered on hickory trees, including the retained lesions and infections remained latent until suitable conditions for symptom development.A total of 107 single-conidium isolates of B.dothidea were further tested for their sensitivities to trifloxystrobin.Trifloxystrobin had weak activity against the mycelial growth of B.dothidea, but during stage of spore germination, the frequency distribution of the EC50 values for 107 isolates was a unimodal curve, ranging from 0.76mg/L to 36.7mg/L with an average of 9.73 ± 1.13mg/ L.Thus, these sensitivity data could be used as a baseline for monitoring the shift of sensitivity in B.dothidea populations.Control of canker disease on Chinese hickory by different fungicide programs indicated that the time of the first spray inhibiting the mycelial growth of B.dothidea is very important which should be done before the initiation of canker lesion expansion and far before the initiation of spore dispersal.And, the following two sprays should adopt fungicides to inhibit mainly the spore germination and somewhat the mycelial growth.