The mantra of free global trade continues to be heard around the world. As part of this philosophy, acronyms have sprung up like weeds across a cultivated field. These include the likes of the North American Free Trade Agreement (NAFTA), The General Agreement on Tariff and Trade (GATT) and now the TransPacific Partner ship. Although globalization is considered by most pundits to be “good,” there is often a price to pay. One is the possible loss of jobs in a region or industry as shifts in labor costs create opportunities for some at the expense of others. Another is the impact of world movement of biological material around the globe. Examples are legion, from humans and mosquitoes to invasive plants, moths and mussels.
Beekeeping is no stranger to this phenomenon. The honey bee itself is an introduced species in North America as are many of the crop plants it pollinates. Across Europe, the introduced plant from the eastern part of the United States (Black Locust) is one of that country’s most important nectar sources . In Florida, the melaleuca tree (Melaleuca quinquenervia), a relative of eucalyptus introduced from Australia, was originally thought to be potentially harmful to beekeeping. The tree’s strong-tasting nectar, it was feared, would contaminate the citrus and palmetto honey crops. The concern was unfounded. Instead, the plant became extremely useful to beekeepers as a prime nectar source for buildup and maintenance in the fall of the year. However, it has also been blamed for everything from being a fire hazard in urban areas to drying up fragile wetlands like the Everglades. Thus, a widespread campaign is underway to rid the state of as much of this “noxious weed” as possible.
Both the tracheal and Varroa mites are introduced species that have greatly affected North American beekeeping. Most certainly their coming was the result of increased movement across the world by ships and airplanes. After introductions of these extremely damaging parasites, it was anticipated that perhaps only a few other organisms might be introduced that would greatly affect North America’s beekeeping industry, the Asiatic bee mites, Tropilaelaps clareae and Euvarroa sinhai, and finally perhaps more worrying Apis mellifera Capensis. These remain on the Animal Plant Health Inspections Service’s (APHIS) list of potentially damaging organisms. Not present on the APHIS list is Aethina tumida, the small hive beetle from South Africa. This organism merited only a few paragraphs in the Second and Third Edition of Honey Bee Pests, Predators, and Diseases (Cornell University Press, 1990, 1997). In his description of this insect in the second edition, Dewey M. Caron wrote, “One can only hope that the beetle will not be transported to other beekeeping areas.” Hope springs eternal, but Aethina tumida showed up in southeastern Florida in the spring of 1998, and Florida agriculture commissioner Bob Crawford formally asked the U.S. Secretary of Agriculture for assistance in determining appropriate regulatory action.
How the small hive beetle made the long trip from its African homeland remains an enigma. The first sign of its presence was a large number of larvae (worms) found in honey extracting rooms. The larvae superficially look like those of the wax moth (Galleria mellonella) and were considered so at first. Both wax moth and beetle larvae can occur together in the same bee colony. On closer inspection, however, it becomes clear these are not the growth stage of Lepidoptera (butterflies and moths) but are in fact that of Coleoptera (beetles). Beetles, like moths and bees, have the kind of insect development called “complete metamorphosis.” This characteristic life Kyle begins with an egg, which hatches into a feeding larva (worm) that completes its development during a resting stage (pupa), and finally emerges as an adult, complete with six legs and two pairs of wings, the reproductive phase. While wax moth larvae have many uniform, small “prolegs,” beetle larvae possess three pairs of larger more pronounced legs near the head. Another difference is that the beetle larvae do not gain as great a size as do wax moth larvae before pupation. They also do not spin a cocoon in the hive, but must complete their development in the soil outside the beehive. The adult beetle is red just after pupation and then turns black. It is fairly uniform in color, moves rapidly across the comb, and is extremely difficult to pick up by hand because it is covered with fine, hair-like spines. It is visible to the naked eye and about a third the size of a worker honey bee.
Originally, A. tumida was found in three Florida counties (St. Lucie, Indian River and Brevard). Quickly it was realized that the beetle was so established that no further activities related to eradication were attempted, although a brief movement moratorium was implemented.
The good news is that the beetle is not considered a problem in South Africa and rarely actively destroys colonies. It is in the family named Nitiulidae, a group known as “sap beetles.” It is also a scavenger and, like the wax moth, must have pollen for protein to ensure its development. The bad news is that it is an introduced species and may be more damaging than in its homeland.
Perhaps the best and most complete study done on the beetle is “The Small Hive Beetle, Aethina tumida,” by A. E. Lundie (Union of South Africa, Science Bulletin 220, 1940, 30 pp.). It appears to be a tropical insect and not reported in temperate areas. This may mean fewer problems for colder portions of North America.
According to Dr. Lundie, the most objectionable behavior of the larvae is that they defecate in honey. This, presumably in conjunction with secretion of other materials into the sweet, eventually results in fermentation and frothiness that has the characteristic odor of “decaying oranges.” The fermented honey runs out of the comb and may pool on the bottom board or honey house floor. At that point, honey bees will ignore the mess and may even abscond. Larvae will heavily damage delicate, newly manufactured comb, causing honey to leak out. However, old brood comb reinforced with bee pupal skins can withstand heavy larval infestation without disintegrating. As a remediation technique, the objectionable, fermented honey can be washed off with a garden hose and the bees will often resume their activity to clean the comb.
Dr. Lundie says that the principal time beekeepers have trouble is when combs of honey stand for long periods in the honey house prior to extraction, especially those that contain pollen. Cappings set aside during the extracting process may also become “wormy.” Honey left over Porter bee escapes for a period is also at risk. All these lead to infestations because honey bees are not available to remove either larvae or adults from the colony. Thus, Dr. Lundie concludes, “Any factor which so reduces the ratio of the population of a colony of bees to its comb surface that the bees are no longer able to protect this comb surface adequately is a precursor to the ravages of both the wax moths and Aethina tumida.”
This is good advice; it already is common beekeeping practice in both Africa and Florida. The bees in Africa, however, are different than those in most of North America. Apis mellifera scutellata, the African honey bee, has radically different behavior from that found in the European Apis mellifera bee, managed by the beekeepers of North America. It is already known that African and Africanized honey bees in the face of even light predation or perturbation readily abscond. In doing so, they leave behind a nest heavily infested with all kinds of possible organisms. Dr. Lundie suggests that this behavior may be a reason why American foulbrood has never taken hold in South Africa.
Scavengers like wax moths and A. tumida remove abandoned nests so quickly that the disease reservoir ceases to exist. European honey bees are not as likely to abscond as African bees; they also may not be as hygienic in the nest. Both are reasons that their relatives Africanized bees are thought to be more tolerant of the Varroa mite . Another African honey bee, Apis mellifera capensis, is also affected by the beetle, but appears also to be withstanding its effects. What does inferior hygienic behavior and the lack of a tendency to abscond portend for North American bee colonies invaded by A. tumida? Dr. Lundie provides a hint of this in his publication, saying that when honey bees cannot eject the beetle easily, strong as well as weak colonies may be equally affected. In addition, even in South Africa, at rare times the beetle can heavily affect colonies. There has been new research revealing that keeping colonies in the shade favors beetle population build up. The relationship of beetles with a particular fungus and apparent ability to locate colonies that are under “stress,” are also important variables in beetle infestation.
The cry for control measures quickly reached a crescendo in affected parts of Florida. This is no surprise when one is confronted with colonies that appear to collapse overnight into a frothy mass correlated with high infestations of beetle larvae. A. tumida is at its most vulnerable when the larvae leave the hive to pupate in the soil, and this probably represents a good starting point for beekeepers to experiment with controlling this insect by cultural means. Perhaps the larvae can be trapped somehow before they reach the soil. Soil conditions also become important; the larvae may not pupate effectively in too dry, sandy or wet conditions. Dr. Lundie reports some indications that larvae infested with a soil-dwelling fungus died. Certain ants or other insects may prey on the larvae. The imported fire ant (Solenopsis invicta) in the southern United States comes to mind.
Dr. Lundie reports that stationary colonies are more vulnerable than those that are moved. Thus, relocating colonies may break the beetle’s life cycle, a classic control measure used elsewhere in agriculture. Certainly the bees’ self-cleaning behavior itself should be used to the utmost. Colonies will probably vary in the ability to withstand infestation and should be monitored for the ability to do so. As part of this, beekeepers should be very careful not to provide more exposed comb than the bees can adequately cover, or purposefully infest a colony that doesn’t already have beetles. The beetle’s arrival could signal a paradigm shift in honey bee management. It is possible that standard practices like stacking empty or weak colonies on stronger ones, making weak splits, and/or liberally exchanging combs may no longer be good options.
Chemical control either in stored supers or live colonies for A. tumida appears to be problematic. There are no registered materials in South Africa, and there has been little research on this front. Beetles appear to be most damaging when supers are full of honey, which is contraindicated for any pesticide application because of possible product contamination. The possibility of killing large infestations of beetle adults and larvae by using pesticides inside a colony, while not harming bees, mirrors the current dilemma in Varroa control.
The arrival of Aethina tumida is not good news for beekeeping in North America. This beetle adds to an already large litany of beekeeping challenges. It is everyone’s hope that this insect will not be a significantly worse problem than in its homeland. Until this is known, however, it must be considered an aggressive scavenger that in many instances will overwhelm even relatively strong colonies of North American honey bees of European extraction. Finally, it is a wake up call. Serious consideration continues to be given to the risk of moving biological material across international borders, and the beekeeping industry should not consider itself immune from this potentially harmful practice.
Latest information is that the small hive beetle has made its way to Brazil, perhaps opening up the whole South American continent to this pest. In addition, Varroa jacobsoni has now been found in Australia, although that is not the most virulent kind. The beat goes on as container ships and human movement put the globe at risk for a variety of reasons.
