Seasonal occurrence of entomopathogenic fungi in apple orchard not sprayed with insecticides
2007
Yagimuma, K.(National Inst. of Fruit Tree Science, Tsukuba, Ibaraki (Japan))
The seasonal occurrence of entomopathogenic fungi in an apple orchard that was not sprayed with insecticides was investigated for six years (1996-2001). During this period, the total number of insect cadavers collected was 10,411, and the collection in 1998 was about ten times that in 1996. The occurrence fluctuated every year, peaking in September 1996 and 1998, May 1997, and August 1999-2001. The common insect cadavers collected were coleopteran (81.7%), lepidopteran (8.7%), hemipteran (5.8%) and dipteran (1.8%). The major species of entomopathogenic fungi isolated from these cadavers were Beauveria bassiana, Paecilomyces tenuipes, P. farinosus, Metarhizium anisopliae, and Hirsutella jonesii, accounting for 87.7, 5.7, 2.4, 1.0, and 0.5% of the total number of fungi, respectively. B. bassiana was isolated mainly from carabids, especially Amara congrna, P. farinosus from lepidopteran, hemipteran, and coleopteran, and H. jonesii from the cydnid bug, Adomerus triguttulus. There was a high correlation between the amount of rainfall and the number of insect cadavers collected throughout the years (r=0.94). Thus, it was suggested that the weather, especially the amount of rainfall, greatly influenced the seasonal occurrence of entomopathogenic fungi.
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