Bee Pathology – pages 171-173
THE TRUTH ABOUT VARROA IN BRAZIL
GONCALVES, L. S.; DE JONG, D. (Brazil)
MORSE, R. A. (U.S.A.)
Varroa is currently recognized to be the greatest problem for apiculture worldwide. First described in Asiatic bees Apis cerana, in Indonesia, by the Dutch researcher Oudemans in 1904, the mite turned into a problem for Brazilian bees, Apis mellifera, in the 1970s. Transfer of the pest from A. cerana, whose infestation is of little economical importance, to A. mellifera occurred when beekeepers carried honeybees to Asia. Today Varroa is found throughout Asia, in most of Europe, in the Northern region of Africa, in several countries in the Middle East and in the following South American countries: Paraguay, Brazil, Argentina, Uruguay Peru and Bolivia.
In 1971, infested hives were brought to Paraguay from Japan. Soon after, in 1972, an apiculturist from Sao Paulo took some of these Japanese bees to the region of Jundiai, thus initiating infestation in Brazil. However, infestation was first detected in 1978 when the pest had spread considerably and there was no way of eliminating this “new” enemy of Brazilian apiculture. At present, Varroa can be found in 18 Brazilian States, from Rio Grande do Sul to Piaui, so that it is too late to avoid transporting hives from a State to another.
Can we blame the Japanese, or other peoples, or even our own beekeepers for spreading so much these bees without taking precautions against possible consequences such as the introduction of Varroa? In a way, we can. All those who work in apiculture should he aware of the possible consequences of their carelessness, especially those involved in ”migrant apiculture” at the international level. A period of quarantine is always recommended to avoid the entry of pests into the country. In 1971, Varroa was little known and the problems of hive mortality, which were already occurring in Russia, were not properly communicated to the Western world. In Eastern Europe also, Varroa was present 4 to 6 years before being detected. Not even West Germany, where apiculture is well organized and controlled, succeeded in containing Varroa.
Research on Varroa in Brazil
The Department of Genetics of the University of Sao Paulo, Campus of Ribeirao Preto, started a research program on Varroa in 1979 under our direction and with the financial support of the Foundation for the Advancement of Science in the State of Sao Paulo (FAPESP) and later of the National Research Council (CNPq). ln 1980, a collaborative program between USP and the Department of Entomology of Cornell University was started, with the financial support of the National Science Foundation (NSF) and later of the Department of Agriculture, USA (USDA). As part of this program, Dr. De Jong came to Brazil in 1980, where he is currently involved in research.
It was soon observed that Varroa had spread considerably but with low indices of infestation. The mite showed no symptoms to the beekeepers who did not know it, since at the beginning of infestation Varroa is present in very reduced numbers in hives, although it rapidly transfers from hive to hive through new field bees which get lost during the first recognizance flights and through drones, which tend to enter other hives.
What is Varroa?
Varroa is an acarid which attacks honeybees. It is a relatively large brown mite 1-mm long and 1.6-mm wide. Varroa feeds on bee “blood” (hemolymph). Normally, only adult females can be seen. The other female stages (nymphs) and males are found only in bee brood cells and are smaller and white. These also feed on bee “blood” (except for adult males which do not feed on anything). When compared with other types of pests, Varroa, reproduces slowly. Under ideal conditions, the mite leaves on average one to two new female descendants per cycle in worker bee brood. Without taking into account mortality or migration to other hives, an infestation starting with a single female may take approximately 400 days to include 5000 acarids. At the same time, many of these females may be moving to other hives, and therefore it would take even longer for an initial infestation to reach a damaging level. Obviously, if infestation started by introduction of well-infested hives into a beekeeping unit of a migratory type, proliferation becomes more rapid. Also, Varroa multiplies more rapidly at the time of drone rearing, with a single female capable of producing 2 to 4 new females in a drone cell.
Our studies have shown that Varroa reduces the weight and mean life of bees that were infested during development. When infestation is low, however, the beekeeper does not detect this damage. When a single larva is attacked by 5 or more acarids it can still survive, but its body, and the wings in particular, will be visibly damaged. However, very few bees are attacked by so many acarids, and when this happens they are thrown out by the other bees, so that the beekeeper will not see the problem.
Hive mortality caused by Varroa
Millions of hives have already died in Europe because of Varroa. Tens of thousands have died in Argentina. In many regions of the world it is impossible to keep bees without treating them. In Brazil thus far, no hive death caused by Varroa has been reported. even though the mite reached Brazil before being introduced into Argentina. A completely unexpected phenomenon has occurred, since greater infestation was expected in our climate, which permits Varroa to reproduce throughout the year, in contrast to countries with cold climates, where Varroa does not reproduce in winter.
Fortunately until now we escaped relatively well, since our levels of infestation with the pest are low, whereas they are very high in the rest of the world. However, Varroa still causes serious concern. Even though the level of infestation is low and does not cause death of hives, there is still damage, because all hives in the country are progressively becoming infested. Infestation causes little damage per hive, but if we sum all the hives, great waste occurs in our apiculture.
We can estimate the damage caused by Varroa as follows: our studies have shown that the mean life of bees infested with Varroa during development is reduced by half. Thus, for each two bees affected, we actually lose one. If 2% of worker brood is infested, the population of the hive will be reduced by 1%. We may estimate that his would cause a 1% reduction in honey production. Since national production in 1984 was estimated at about 30,000 tons, the reduction would be approximately 300 tons which, at the cost price of Cr$9,500.00 per kilogram, would cause a loss of about 3 billion cruzeiros (about 300,000 US$). The ideal would be for all beekeepers to be able to treat their bees to save them and to guarantee honey productioin. However, the solution is not so simple, since so far there is no adequate pesticide for the conditions prevailing in Brazil. Either the treatment is too expensive, or is harmful for the bees, or it contaminates the honey. If one opted for treatment with chemical products, such treatment should be applied every year, at a cost that would be higher than the loss caused by Varroa.