In 1997 a deadly parasite entered South Africa, possibly sneaking into the country at Simonstad harbour in the Cape. Known as Varroa destructor, this small tick-like mite sucks the blood out of honeybees, and has been considered to be the most serious parasite of honeybees in the 20th century. When it invades colonies, they usually collapse within a matter of a few years.
This international menace has now been found in the Kruger National Park. Honeybees are extremely important in agriculture for the pollination of commercial crops, as well as for their honey producing ability. In South Africa, it is estimated that honeybees are also responsible for pollinating over 60 percent of indigenous flowering plants.
The loss of honeybees might have disastrous consequences for South Africaís floral diversity, and thus all the animals that rely on plants. The varroa mite has been responsible for the collapse of beekeeping industries around the world, and in America the only bee colonies left are found in the hands of professional beekeepers who use pesticides to kill the mite. Wild swarms become infested with the mite and die over a period of time.
When detected in the Cape in 1997, it was the first record of the varroa mite in sub-Saharan Africa. In August 2000 the first mites to be detected in the Kruger National Park were found in a hive near Numbi Gate by Dawid Swart from the Agricultural Research Council.
The mite usually travels around with beekeepers, spreading to new regions when the beekeepers move their hives to produce more honey or to pollinate specific crops. is suspected that varroa may have entered the park from a commercial beekeeping venture outside the park in the Numbi area. However, it is now in the wild bee population and can spread throughout the park, potentially killing all the bees in the park.
The mite usually spreads when drone (male) bees leave the hive that they were hatched in for another hive. When the mite was first detected Kruger, the colony of bees containing the parasite was killed in an attempt to slow the spread of the mite in the park. At that stage, was estimated that there were only about dozen mites in an entire colony of several thousand bees.
Despite the low numbers mites and the destruction of the colony, 2002 varroa was found in two new localities, north of Pretoriuskop and between Pretoriuskop and Afsaal. By 2003 the mite had been detected Skukuza, many kilometres both north and east of where it was first found. Given the potential for destruction that the mite can have, from the time the first case was found, monitoring of the bees in the park took place.
This was initially carried out Dr Per Kryger from the University of Pretoria, along with the scientific services department of the park, especially the invertebrate research department, now managed Hendrik Sithole. The speed at which the mite would move in a natural population bees was not known when the project began. 300 bee boxes that had been used for previous research into the wild bee populations in the park are being used for the ongoing monitoring of the varroa mite.
The bee boxes provide new homes for swarming bees, and can be easily accessed by researchers. monitoring bee populations in the boxes over time, researchers can find out how fast the varroa mite destroys a bee colony, and also how fast the mites spread. Twice a year the boxes are checked colonies, to estimate the density of bees the park. This would allow the park to be restocked by man in a worst-case scenario where all the bees in the park died because of the mite.
It also allows scientists to find out what effect natural diseases and other factors have on bee populations. Colony density can be inferred by checking the workers in hive. Dr Vincent Dietemann, also from the University of Pretoria, takes a few workers from each hive and looks at their DNA. By seeing how genetically different the worker bees are they can determine how many male bees mated with a queen bee before she established her hive.
As the male bees would have come from different hives, the scientists can find out how many colonies produced the drones, giving an estimate of the colony density. The colonies in the boxes are also inspected for the presence of mites, to see how fast the mites are spreading. The CyberTracker system carried by the field rangers in the park has also played a role in the research. If rangers out on a daily patrol find bees, they enter them into their handheld cybertracker computers, which records the precise location of the sighting.
The information is then downloaded into a database that creates a map. With the help of the rangers, the researchers would like to build up a database not only of bee sightings, but also of the presence of natural hives. Over the course of time, as the varroa mite is not immediately deadly to bee colonies, but takes a few years to wreak havoc, the scientists will be able to tell if wild African honeybees have any resistance to the mite.
This would help inform the rest of sub-Saharan Africa, when the varroa mite enters colonies further north. Mike Allsopp, from the Agricultural Research Councilís Honeybee Research Section, has found in the course of his research in the Cape that Cape honeybees have developed resistance to the varroa mite.
His paper presented at the Entomological Society of Southern Africaís 2003 congress said that it was the first case of fully documented mite tolerance anywhere in the world. However, the bees that occur in the Kruger National Park are a different subspecies of bee, and there has been no evidence yet that they may be resistant to the deadly Varroa destructor.