Chalkbrood and Stonebrood


Chalkbrood and Stonebrood are fungal diseases of honeybees (Apis mellifera) that occur worldwide. Chalkbrood is caused by Ascosphaera apis and affects the brood.
Stonebrood is caused by Aspergillus flavus and Aspergillus fumigatus and affects both the brood and adult bees.

This practice describes the causes and symptoms of Chalkbrood and Stonebrood, how they spread, how to address and prevent these diseases.


1. Chalkbrood


Bee larvae become infected by ingesting spores of Ascosphera apis with food. The spores germinate in the intestines leading to the death of the larvae.  Each dead larva of chalkbrood produces billions of spores and, if not removed by the worker bees, they can remain infectious for several years within the hive.

Ascosphera apis grows better in larvae situated more externally in the brood because it is colder. This phenomenon may occur especially during the colony spring growth, when the number of adult bees is not enough to allow an adequate nest temperature control to cover the whole brood area. Less populated and weaker colonies are more susceptible as the bees are not able to keep all brood warm. Drone larvae are usually the most affected because of their location on the margins of the brood chamber. 


The larvae may be affected in different life stages, more frequently on the 3rd or 4th day of larval life. They then die in the first two days after capping, so bees must uncap the cells to remove the dead larvae. Chalkbrood produces a mummification and/or calcification of the larvae (Fig. 1). Firstly, larvae appear soft, assuming the hexagonal shape of the cell, then they dry out and become hard. The larger part of affected larvae appears white, but some become grey or black (Fig. 2); they may not present any symptoms if the infection is less than 12%. The presence of little stones (chalkbrood) on the bottom or at the entrance of the hive is typical.


The disease is influenced by the genetics of the queen, like hygenic behaviour that is able to prevent or contain the disease by removal of affected larvae. Moreover, low temperatures, high humidity in the apiary and poor ventilation of the hives all contribute to the disease being more severe. Avoiding any practice that causes heat loss in the colonies can help prevent chalkbrood disease. Some practices include: too many / too long hive inspections during winter time or during cold days, colony splits for artificial swarming and nest enlargement with interposition of wax combs between brood combs (especially during unfavourable periods for wax comb construction such as early spring, autumn or winter, when the bees do not find enough food resources). Chalkbrood and Stonebrood may even appear in the hives after antibiotic treatment due to a lack of microbial competition.


Many drugs have been tested, but the persistence of spores makes the disease eradication impossible. The best solution seems to be the administration of sucrose syrup (1:1) acidified with lemon juice or vinegar or ascorbic acid powder until pH4, and prevention with the application of good management practices in the apiary, such as the selection of appropriate locations, selection of resistant queens and ensuring enough food reserves in the hive (also feeding artificially when necessary). This disease, as well as stonebrood, frequently causes constant spring losses but the evolution of the disease is usually benign: affected colonies can recover by themselves especially if they increase their population (e.g. in favourable environmental conditions as in sunny days of spring-early summer with presence of abundant nutritional resources).

Fig. 1: Calcification of the larvae (Photo source Dr. Palazzetti - ASL VT, Italy)

Fig.2: Some larvae become grey or black (Photo source Dr. Palazzetti - ASL VT, Italy) 


2. Stonebrood


Stonebrood is a disease present worldwide and caused by the fungus Aspergillus flavus or, less frequently, Aspergillus fumigatus, both commonly disseminated in the soil. The temperature limits for its development are between 7° and 40° C; with an ideal range around 33°-37° C.

Stonebrood can affect larvae as well as adult bees. The infection is oral by feeding (from one bee to another by passing nectar) or cleaning the hive, but the fungus are also able to develop at the surface of the bees‘ body, causing the damage from the outside.

It affects capped and un capped brood. At the beginning the larvae appear white and fluffy, then they become yellow (A. flavus) or greenish brown (A. fumigatus), mummified and with a hard consistency. The appearance is very similar to the chalkbrood affected larvae (Figure 1 and 2). Behavioural changes are observed in adult bees: agitation, weakness, paralysis, inability to fly away from the hive and morphological alterations with distended abdomen and subsequent mummification.


There are no treatments to eradicate the disease that is transitional and disappears spontaneously, but the correct apiary location (avoidance of wetlands and good exposure), proper management (preventing water infiltration inside the hives) and the regular disinfection of beekeeping equipment (eg. sterilising by torch flames) are effective prevention measures. Although death of entire colonies affected by the fungus may occur, the disease is usually transitional and subsides spontaneously, especially if the previous measures are applied.


This technology was developed by Formato G.1, Milito M.1, Menegotto A. 2, Jorge Rivera-Gomis1, Jannoni-Sebastianini R.3

1 Istituto Zooprofilattico Sperimentale del Lazio e Toscana “M. Aleandri” - Italy

2 Conservation Global - South Africa

3 Apimondia - The International Federation of Beekeeper’s Associations - Italy


Further reading

See also the moderated discussion: Simplified field methods for diagnosing honey bee diseases and GBPs to prevent them:



Created date

Thu, 26/10/2017 - 15:19



Apimondia, the International Federation of Beekeepers’ Associations, is the world organisation representing the interests of apiculture and aims to facilitate links between beekeepers, scientists and all involved with apiculture. Apimondia stems from the International Committee of Apicultural Congresses created in 1893 holding the first congress in 1897 in Belgium. Apimondia in its current institutional form was founded in the Netherlands in 1949 and its core business is the organisation of international apicultural congresses and symposia. Today Apimondia work remains truly international: Apimondia is run on a basis of co-operation between beekeepers and scientists from many countries as well as international organisations. A special feature of Apimondia is the wide range of working languages used in publications and at meetings.

You can also visit Apimondia linked websites to find out more:



Apimondia, la Federación Internacional de las Asociaciones de Apicultores, es la organización mundial que representa los intereses de la apicultura y su objetivo es facilitar los vínculos entre los apicultores, los científicos y todos los involucrados con la apicultura. Apimondia deriva del Comité Internacional de los Congresos Apícolas creado en 1893 y con la celebración del primer congreso en 1897 en Bélgica.  Apimondia, en su forma institucional actual, fue fundada en los Países Bajos en 1949 y su actividad principal es la organización de congresos y simposios apícolas internacionales. Hoy el trabajo de Apimondia permanece verdaderamente internacional: Apimondia realiza su programa sobre la base de la cooperación entre los apicultores y los científicos de muchos países, así como organizaciones internacionales. Una característica especial de Apimondia es la amplia gama de idiomas utilizados en las publicaciones y en las reuniones de trabajo.

Para más informes puede visitar los sitios web de Apimondia:

Contact person: 
Riccardo Jannoni-Sebastianini
Contact email: 
Contact person: 
Apimondia Secretary
Contact email: 

IZSLT - Istituto Zooprofilattico Sperimentale del Lazio e della Toscana “Mariano Aleandri”

The Istituto Zooprofilattico Sperimentale del Lazio e della Toscana “Mariano Aleandri” (IZSLT) is a public body operating in the frame of the National Health Service with duties related to animal health and welfare and food safety. In such areas it provides services in the diagnosis of animal diseases and zoonoses, microbiological, chemical and physical controls over safety of foods, food production chains and animal feed. In the same areas it performs research, epidemiological surveillance, continuous training and international cooperation activities.

IZSLT's mission is to ensure that animal health and welfare, hygiene of farms, primary productions, safety of foods and animal feed comply with the relevant legislation.

To effectively fulfill its mission, the Institute carries out:

  • diagnostic service over animal diseases and zoonoses;
  • scientific and technical support to veterinary and public health services for controls on animals, food and feed;
  • laboratory tests to verify the health status of animals;
  • technical and scientific support to monitor veterinary medicines;
  • research on animal health and welfare, food safety and hygiene of farming and livestock products;
  • studies on animal welfare and development of alternatives to the use of animals in experiments;
  • studies to monitor the safety of food of animal origin and feed;
  • scientific and technological cooperation with other research institutes;
  • epidemiological surveillance on animal health and food safety, on livestock products and on environmental factors affecting the above;
  • studies on the health risks for humans linked to animals and animal products;
  • support, technical assistance and hygiene information to manufacturers of food of animal origin;
  • production of vaccines and laboratory diagnostics for the improvement of animal health.

In the frame of IZSLT activities, the Apiculture Unit’s mission ( is to certify and guarantee the health and welfare of bees, and the hygiene and safety of the hive products, through: diagnosis of bee diseases and analyses on hive products, support to Governmental Institutions in drawing up legislation, research activity, collaboration with other laboratories or institutions, technical support and training for operators, pollution environmental monitoring using honey bees and protection of honey bee biodiversity.

Contact person: 
Giovanni Formato