Effect of temperature and humidity of sealed brood on chalkbrood development under controlled conditions

This paper reports improvements on a previous technique of ours for producing chalkbrood disease in Apis mellifera under controlled conditions. Mummification reached almost 95% (the previous technique reached 70%) when fifth instar larvae were chilled at 18 degrees C 24 h before sealing and kept at 25 degrees C for 6 days after operculation. When the larvae were chilled, but the temperature after operculation was 30 or 35 degrees C, mummification reached 43.65 and 29%, respectively. Percentages of mummification were lower when chilling prior to sealing cells was not applied: 77.62% (at 25 degrees C after sealing), 15.31% (at 30 degrees C) and 2.22% (at 35 degrees C). The effect of a high relative humidity (rh) (87%) combined with slight chilling (30 degrees C) induced a higher percentage of mummification (7.75%) then compared to the same temperature but lower rh (only 0.95% of larvae were mummified at 68% rh).