VII Brazil Congress: the latest on Varroa jacobsoni

The following summary of information presented at the recent Congress (7-11 October 1986) is prepared by William Ramirez B, Escuela de Fitotecnia, Universidad de Costa Rica.

De Jong¹ gave a review of the Varroa problem. According to him: “In general it appears that in cold and temperate climates, the populations of Varroa grow without limit to the point of killing colonies of bees. However, in tropical climates the infestations persist in moderate levels causing reductions in the production but not the colony death”.

Issa and Goncalves² presented a short paper about the reaction of Varroa jacobsoni to external stimuli. Mites are able to detect bee larvae at short range (about 3mm or less; few mites react at distances of 4.5mm). Another evident reaction of female Varroa is to air currents (especially human breathing air). The mite turned 180° towards the stimulus.

Ramirez³ presented the results of combating Varroa with dusts. He reported that Varroa, as well as feather, hair and skin mites parasitic on other animals have tarsal pads which allow them to adhere to the substrate. When Varroa comes into contact with dust on bees and the hive, the dust adheres to the pads, this results in the mites losing their points of attachment and equilibrium, and dropping from the bees and combs to the bottom of the hive, where they die or are carried away by small ants. Once a female Varroa turns on her back, she cannot right herself. 50cc of a variety of products were dusted on hives. Glucose reduced the population of phoretic mites by 100%; pollen substitute (Proteinni) by 97%; ground leaves of Casuarina cunninghamiana by 95%; and ground pollen by 87%. The results were obtained 14 hours after the application of the products. Other bee mites eg Euvarroa sinhai, Tropilaelaps clareae and T. koenigerum also have tarsal pads like those found in Varroa and could also be controlled with dusts.

Message ef al⁴ described the effect of Varroa jacobsoni on honey production by Africanized bees over a 15 month period. The average infestation on the hives was 5.5% and 9.9% for brood and adult bees Tespectively. There was a positive correlation between the amount of honey produced and the rate of infestation in the adult bees when the infestations were low. It was found that the correlation was indirectly due to the amount of capped brood. They concluded that Varroa is not affecting honey production by Africanized bees.

Peixote⁵ described the use of a dry formula composed of one part Fitalomicina and five parts refined sugar, which is dusted over the frames to prevent and cure sacbrood, European foul brood and possibly American foul brood in “‘belas rainhas duradas” (probably Italian bees). He informed that ‘normally, with the first three applications of dust the hive will be cured”’.

It was announced at the symposium that thirty years after the introduction of the African bee in Brazil, European bees and Varroa jacobsoni had been simultaneously introduced to the island Fernando de Loronha, Brazil, to try and develop strains of European bees resistant to Varroa.

References

1. De Jong,D.; 1986. Uma Visao Mundial do problema “Varroa”. VII Congresso Brasileiro de Apicultura. Salvador. Bahia, Brasil: 53.

2. Issa,M.R.C.; Gonglaves,L.C.; 1986. Reagao do acaro Varroa jacobsoni a estimulos externos. VII Congresso Brasileiro de Apicultura. Savador Bahia, Brasil: 53-54.

3. Ramirez,B.W.; Otis,G.W.; 1986. Developmental phases in the life cycle of Varroa jacobsoni, an ectoparasitic mite on honeybees. Bee World 67 (3): 92-97.

4. Message,D.; da Silva,H.; Gongalves,L.S.; 1986. Efeito do dcaro Varroa jacobsoni na produgao de mel em colonias de abelhas africanizadas (Apis mellifera). VII Congresso Brasileiro de Apicultura. Salvador Bahia, Brasil: 55-56.

5. Peixote,P.P.; 1986. Fitalomicina: uma esperanga no combate a mortalidade de larvas de Apis mellifera. VII Congresso Brasileiro de Apicultura. Salvador, Bahia, Brasil: 54.