Stone brood disease is also known as stone disease and stone bee disease. The disease can infect not only larvae, but also pupae and adult bees and die. At present, the disease is mainly distributed in Europe, North America and China, and only occurs in western bees.
1. Pathogens
Aspergillus bee is mainly caused by Aspergillus flavus, but also by Aspergillus fumigatus. The morphological characteristics of Aspergillus aflatophyllus are: colonies are velvety yellow-green, dark cinnamon on old cultures, and light grayish white in infertility areas. The conidia stalk is 0.4 to 0.7 mm long, light-colored, warty, 7 to 10 μm in diameter, sometimes separated. The parietal sac is round or flask-shaped, rarely with a slightly blunt end, 30 to 40 microns in diameter, small stems do not branch, are tightly packed together, radial on all sides, 20 microns long, 6 microns in diameter, 1 or 2 layers. The conidia are mostly spherical, smooth, and have particles, 4 to 8 microns in diameter (mostly 5 to 6 microns), and are easily broken chains.
Aspergillus fumigatus resembles Aspergillus aflatophyllus under the microscope, but its colony color is gray-green.
Aspergillus aflatogenes grows well on general potato medium, and its spores are extremely resistant to adverse environments, and it takes 5 minutes to kill them in boiling water, and it can be inactivated in general disinfectant for 1 to 3 hours.
2. Symptoms
Larvae with aflatoxine may be capable or uncaptured, and pathogenic bacteria can sometimes infest pupae. At the beginning of the disease, the larva becomes soft, then the body color changes to a pale brown or yellow-green color, and after the larvae die, the body loses water and becomes very hard, and the surface of the insect corpse is covered with villous yellow-green mold and spores. Aerophytic hyphae attach the worm carcass to the wall of the nest.
The most significant symptoms of adult bees after illness are abnormal commotion in worker bees, weakness, paralysis, and often swelling of the abdomen. Spores form the earliest and most abundantly near the head. The abdomen of a dead bee often appears to be dry and hard like the entire body of the larvae, the dead bee does not rot, and the surface of the body is covered with hyphae and spores.
3. Pathogenic growth
Bees become infected as soon as they swallow spores. After the spores germinate in the digestive tract, the resulting hyphae will damage all soft tissues. Moreover, spores can also germinate on the surface of the body, and the mycelium invades the tissues directly from the internodes.
When pathogenic bacteria invade the tissue, the abdomen of the larvae and adult bees stiffens. In the infected larvae, the fungus grows quickly, rapidly penetrates the surface of the body, forms a yellow-white ring behind the head, and within 1 to 3 days, the mycelium envelops the entire larva like a layer of false skin.
The main cause of bee death by Aflatoxin is that the aflatoxin released during growth poisons the bee body and kills. The hyphae have a mechanically damaging effect on all soft tissues, hastening the death of bees.
4. Transmission route
The spores of Aspergillus aflatophyllus are widely present in nature, such as moldy grains, peanuts, etc. The spread of bee aspergillus aflex in nature may be that spores that spread freely with air currents infect bee colonies, or that the spores first contaminate pollen and then infect the larvae or themselves through worker bees feeding or self-feeding. It is even possible that the powder chamber on the nest spleen is where Aspergillus flavus first multiplies.
5. Diagnostic methods
The first is to make a diagnosis based on typical symptoms.
The second is to pick the yellow-green substance on the surface of the disease and insect, place it on a glass slide for water immersion, and observe the morphology of the pathogenic bacteria under a 400-fold microscope to confirm the diagnosis.
6. Prevention and control measures
A small number of disease groups should be burned, and the beehives should be disinfected.