1992/10/01 by P. F. Torchio, Phillip F. Torchio
Agricultural and Biological Sciences · Biochemistry, Genetics and Molecular Biology · #Insect and Pesticide Research #Plant and animal studies #Insect and Arachnid Ecology and Behavior
paper · doi:10.1093/ee/21.5.1086
The causative agent of chalkbrood in the mason bee Osmia lignaria prop inqua Cresson is a fungus recently named Ascosphaera torchioi Youssef & McManus. The present study was undertaken to devise a methodology to measure the infectivity potential of this fungus accurately, based on laboratory experiments designed to assure consumption of all spores by host larvae reared under nonstressful environments. Doses of 10, 100, 1,000, 10,000, and 100,000 spores per cell were tested, and the influence of temperature was measured by exposing replicate treatments to 20, 25, or 30°C. The levels of A. torchioi infection obtained in this study (0.36–8.5%) showed a linear correlation with increasing dose, and these low-level infections overlapped chalkbrood rates found in large field populations studied over a 15-yrperiod (0.4–2%). The infection rates reported in this study (0.36–8.5%) are, however, much lower than those induced in a recent series of related laboratory studies (57%). Causes for the large discrepancy of results obtained in this study versus results reported in earlier studies are attributed to previous experimental designs in which host larvae were reared in stressful environments, producing larvae of reduced vigor which resulted in enormous increases of chalkbrood mycosis.