3.2.2. Collecting bee samples
Because HBTM infestations are influenced by the age of bees, the location within the hive from which bees are sampled should be considered. Since queens can be found on honey frames, it is recommended to examine frames of the entire colony to find the queen before taking any samples; this will ensure that the queen will not end up in the sample jar. Collect adult drones for sampling as well, as they tend to have higher mite abundance than worker bees (Royce and Rossignol, 1991; Dawicke et al., 1992). However, because drones are seasonal, adult worker bees are most often sampled for detection or surveillance purposes.
- Collect about 50 bees from frames in the honey super or from the inner covers where older bees congregate. Highly-infested, older bees will have darkened trachea and many stages of mites, although some of the younger female mites may have migrated out of the tubes.
- If young nurse bees (found in the broodnest) are present, these young bees may only have foundress mites that just started reproducing. The presence of one foundress or a foundress and an egg near the opening of the trachea may be difficult to detect. Thus, to determine mite abundance (number of mites per bee) or mite intensity (number of mites per infested bee), it is best to sample bees from the honey and pollen regions of brood frames, where a good mixture of young and old bees is generally found.
- Collect bees by using portable insect vacuums (Fig. 9) or by scooping bees with a plastic cup directly from the frames or inner cover.
- Place samples into vials or plastic bags or sample directly into a wide-mouth jar containing 70% ethanol. Label each container or plastic bag with location, colony number and the date the samples were collected.
- Although bees can be preserved in 70% alcohol, fresh or frozen bees are easier to dissect. Examination of tracheae is easier when no alcohol is inside them. Bees stored for a long time in alcohol will have darker muscle and tracheal tissues, making the mites harder to detect.
- If molecular techniques are used for mite detection, bee samples should be stored in a refrigerator at 4°C or frozen at -80°C. Storage containers are similar to those used for varroa (see Dietemann et al., 2013).
Fig. 9. Sampling bees for HBTM using a modified portable car vacuum, which collects bees directly into a plastic vial (Photo of S Cobey by D Sammataro).