6. Pathogenicity, control and association with pathogens
Tropilaelaps mercedesae (formerly known as T. clareae) may infest as much as 90% of the brood in A. mellifera colonies (Kiprasert, 1984), but smaller brood infestation levels of 3 to 6% have been consistently reported from A. dorsata colonies (Underwood, 1986) and adult A. dorsata and A. cerana workers show greater resistance to the mite than A. mellifera workers (Khongphinitbunjong et al., 2012). High infestations of A. mellifera brood by this species often results in callow adult bees with deformed wings (De Jong et al., 1982; Burgett et al., 1983) and reduced body weights (Kiprasert, 1984) (see Fig. 10). Untreated infestations rapidly increase to high levels and invariably lead to the death of entire colonies (Atwal & Goyal, 1971; Ritter, 1988; Woyke, 1985a, 1985b).
The control of Tropilaelaps mites in A. mellifera colonies has been reviewed by De Jong et al., (1982) and Ritter and Sneider-Ritter (1988), but is in need of revision. Many of the various synthetic chemical acaricides used to control Varroa mites are also effective against Tropilaelaps mites (Pichai, et al., 2008). Sulphur, formic acid and thymol have also proved satisfactory (Atwal and Goyal, 1971; Raffique et al., 2012). Non-chemical means of controlling T. mercedesae in A. mellifera colonies have been achieved by interrupting the brood cycle of the bees. For example, Woyke (1984; 1985a & b) controlled T. mercedesae in A. mellifera colonies by removing all brood for 2 days, but removal for 5 days is recommended in order to kill all mites. Such methods would probably not be viable for commercial beekeepers that manage large numbers of colonies and they are very time-consuming.
There have been few studies on the pathogens associated with Tropilaelaps. However, like Varroa mites, Tropilaelaps mites have been associated with spread and infection of deformed wing virus in A. mellifera colonies (Dainat et al., 2009; Forsgren et al., 2009). Methods involved with studying bee viruses can be found in Dietemann et al., (2013).
Fig. 10. Damage caused by T. mercedesae to A. mellifera brood. Photo: Denis Anderson.