Length of Stay of the Parasitic MiteTropilaelaps ClareaeOutside Sealed Honeybee Brood Cells as a Basis for its Effective Control

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Abstract
Infestation of honeybee (Apis mellifera) brood and of adult workers by Tropilaelaps clareae and Varroa jacobsoni was investigated in colonies in north Vietnam. All brood combs were removed from six infested colonies, and worker bees and mites from these combs brushed on to one uninfected brood comb which was then placed in each colony. Ten and eleven days later, the age of brood infested by mites was determined; thus the length of the mites' stay outside the sealed brood cells could be directly established. The ratio of number of workers to number of brood infested by T. clareae was one-tenth of that for V. jacobsoni indicating that T. clareae mites remained outside sealed brood cells for only about one-tenth as long as V. jacobsoni or around 1–3 days compared with 13 days. Eighty % of cells infested by T. clareae were sealed within two to three days after the new comb was introduced, whereas 80% of cells infested by V. jacobsoni were sealed within eight days, supporting the conclusion that T. clareae remained outside sealed brood cells for a much shorter time than V. jacobsoni. Chlorobenzilate killed T. clareae and V. jacobsoni mites to the same extent. The lack of success in earlier studies in controlling T. clareae by drugs in the presence of brood was not due to the mite's resistance, but rather to the short period of activity of the drugs and failure to use proper intervals between successive treatments. Effective control of T. clareae in honeybee colonies with brood could be obtained with drugs of prolonged continuous activity which would kill successively emerging mites during their short stay outside sealed brood cells. However, control of T. clareae without medication, by depriving colonies of all brood, is recommended.