Chalkbrood development in honeybee brood under controlled conditions

Abstract

Summary — Third instar larvae from a honeybee colony were fed with high doses of spores of Ascosphaera apis, the causative agent of chalkbrood disease. Optimal survival of spores was detected during a short period after sealing the cell and before larval spinning by culture of the gut contents removed from 4 stages of brood development. The inocula (5 x 10 5 spores/larva) did not induce the disease and were not present in the digestive tract before pupation. In a second experiment, third instar larvae, fed with the same amounts of spores as before, received a cooling stress (22 ± 2°C, for 24 h). When chilling was applied 24 h before or after operculation, mummification occurred in the majority of larvae (59.6 and 65.5%, respectively). Chilling of older brood (spinning larvae or pupa) produced a much lower incidence of chalkbrood. This confirms the need for predisposing conditions over a short period of brood development for the development of this disease. chalkbrood / Apis mellifera / Ascosphaera apis / predisposing conditions / stress / brood chilling INTRODUCTION

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

“…Each larva was fed with a homogeneous suspension of 5 x 10 5 spores mixed with honey (Puerta et (Bailey, 1967;Heath, 1984;Puerta et al, 1994). Although temperature in the brood area can fluctuate between 35.5 and 18 °C (Cooper, 1980), the optimal temperature range for brood rearing is 30-35 °C (Winston, 1987).…”

“…Development of chalkbrood in Apis mellifera requires predisposing conditions; the presence of spores of Ascosphaera apis is not enough to induce the disease (Heath, 1982;Puerta et al, 1994). Chilling of brood and high humidity have been indicated as two of the main predisposing factors by many authors and are reviewed by Heath (1982).…”

“…In this paper, additional studies were made of the effect of the intensity and duration of cooling on chalkbrood expression, improving the technique described before (Puerta et al, 1994). Moreover, a preliminary study of the influence of humidity on chalkbrood under controlled conditions was made.…”

Short communication. Viability and pathogenicity of Ascosphaera apis preserved in integral rice cultures

“…In addition, the development of the disease requires a predisposing condition in the susceptible larva (Heath, 1982). Larvae in the 5 th instar, prior to and some hours after cell capping, are more susceptible to the stress factors that can trigger disease expression (Bayley, 1967;Puerta et al, 1994;Flores et al, 1996). Many factors have been suggested as causes of stress such as excessive moisture, weak colonies, presence of other diseases, inadequate nutrition, excessive colony manipulation (Gilliam, 1990) and chilling of the brood (Bailey, 1967;Flores et al, 1996).…”

“…MY20 agar (Raper andFenel, 1965, cited by Bissett, 1988) is the most frequently used medium (Takatori and Tanaka, 1982;Bissett, 1988;Lee et al, 1989;Alonso, 1991;Alonso et al, 1993;Puerta et al, 1994), but A. apis colonies start to show aging signs after 30 days of growth . Because A. apis cultivated on integral (or brown) rice did not show signs of aging after 60 days of incubation , this medium may be promising for culturing and maintaining A. apis.…”