When most people think of honey bees, they think about the adult bee, but the brood deserves much more attention. Honey bees have certain behaviors that are necessary to keep the brood alive, such as feeding the brood and cleaning the cells after the brood have emerged, but there are certain pests and diseases that effect the brood, where human intervention is needed to prevent colony losses. The beekeeper can help the colony by routine inspections for identification of issues and using an integrated pest management (IPM) plan. Researchers can also help identify the most effective management practices to use.
It Takes a Village to Raise Brood
The honey bee queen lays eggs upright, the eggs soon lean over, and after 3 days hatch into larvae. The larvae start out curled up at the bottom of the cell and consume food from the bottom of cell or directly from nurse bees; the larvae molt 4 times throughout this stage. Healthy larvae should appear full bodied, firm, with distinct segmentation, pearly white, and moist. Queen and worker bee cells are capped after approximately 8 days, and drone cells are capped at approximately 10 days. The larvae spin a cocoon on the walls of the cell and pupate after the 5th molt. From pupal form, the bees molt again to become adult bees. Development from egg to adult bee typically takes 16 days for queen bees, 21 days for worker bees, and 24 days for drone bees.
A honey bee colony needs adequate amounts of honey and pollen to raise brood, and if a colony is low on reserves, it will reduce production or even cannibalize its brood. A healthy brood pattern is consistent with larvae of similar size, with the eggs laid in concentric bands from the center of a frame, with each band around the same age. Issues can be identified by any changes to the appearance of the brood within the cell and the pattern of the brood throughout the hive. There are also many pests and diseases that affect the brood and rely on the brood cycle for reproduction. There are certain symptoms of pests and diseases that can be observed and techniques that can be used to properly identify a pest or disease. The following are a few brood diseases and ways to identify within the bee colony.
American Foulbrood (AFB)
Examining the brood can help identify AFB. If brood is discolored and dying, and cappings are perforated with small holes and sunken with greasy appearance, the colony may have AFB, but these symptoms can also be seen with other diseases. Better ways to identify AFB are by finding a brown/black flat scale that adheres tightly to cell wall and is difficult to remove. AFB is also identified by using the ropiness test. The ropiness test is done by stirring the diseased brood tissue, in the cell, with a stick and removing it slowly, if there is a glue-like consistency that strings out ~2cm, then the colony likely has AFB. Samples can also be sent into AFB programs for laboratory diagnosis. If AFB is suspected or identified, it must be reported by law to the appropriated authorities, usually your provincial apiarist.
European Foulbrood (EFB)
Infection of EFB is not easily distinguishable. The midgut of the honey bee larvae can be seen through its translucent body. EFB can be seen as a chalky white mass in the midgut. When food is abundant infected larvae emerge as adults but their cappings are darkened by bacteria and adults are smaller and lighter in color. If the larvae are not overfed, they die of starvation usually before the cell is capped. The larvae turn yellow/brown and can be seen twisted around cell wall, lying across the mouth of the cell, or stretched out from the mouth to the base of the cell. The larvae color darkens to brown and dries into a scale that is rubbery and easy to remove. When using the ropiness test, EFB shows a watery consistency in the diseased brood.
Chalkbrood
Infection of chalkbrood is easy to identify. The infected brood can be seen as black, grey, or white mummies on bottom board, in pin-holed cells, or outside the hive entrance. In the cell, the anterior part of the bee that is facing up is usually dry and yellow.
Varroa mites
An infestation of varroa mites can lead to symptoms of spotty bee brood patterns, and deformed adult bees, due to increased levels of viruses vectored by varroa mites feeding on the honey bees. Visual inspections are usually insufficient to detect levels of varroa that are damaging. Varroa mites are usually in the capped cells or on the bottom of the abdomen of adult bees, so they are difficult to spot. The best way to identify a varroa infestation is by doing varroa sampling by using an alcohol wash, ether roll, or installing a sticky board in a screened bottom board. More information on testing for Varroa and economic thresholds can be found in the Summer Disease and Pest Monitoring in Honey Bees Factsheet by ATTTA.
Next week’s blog will discuss the life cycles of the pests and diseases mentioned above.
Connecting with ATTTA Specialists
Pernal, S.F. and Clay, H. (eds). 2013. Honey bee diseases and pests 3rd Edition. Canadian Association Professional Apiculturists, Beaverlodge, AB, Canada.