Small hive beetles are considered as one of the the most destructive pests of honey bees, Aphis mellifera L. and they are scientifically known as Aethina tumida Murray (Coleoptera: Nitidulidae)(Ellis and Delaplane, 2008). This beetle is native to South Africa but it has also been found in the North America since 1996. Since 1996, these beetles are known to cause a serious economic damage to Apiculture (Beekeeping) industry in the United States. Young and mature adults of small hive beetles are light brownish red and dark black in color, respectively. Fully grown larvae (also called as grubs) of small hive beetles are whitish, about 9-10 mm long and 1.5- 2.0 mm wide. Pre-pupal stages are creamy white but mature pupae are dark brown in color. Both larval and adult stages found in active beehives but mature larval and pupal stages are found about 3 feet away from and around a beehive and 10- 20 cm deep in the soil.
Immediately after emerging from pupae, young adult beetles enter into active honeybee colonies. These adults generally use their olfactory system to find honeybee colonies by smelling their favorite foods including honey and pollen and by detecting honeybee alarm pheromones. After locating hives, beetles enter into the bee colony and hide in the cracks and crevices of colony boxes to avoid attack from soldier honeybees. In these cracks, hive beetle adults mate and their females lay eggs. Females of small hive beetles generally lay over 1000 eggs in their life-time. Depending on the temperature, these eggs hatch into small larvae within 2-3 days. Immediately after hatching from eggs, young larvae (grubs) enter into the honey comb and start feeding on honey, pollen and broods. These larvae mature in a couple of weeks and then move into soil for pupation. In the soil, pupal stages generally last for 3-4 weeks. The young adults of emerge from pupae and immediately move into honeybee hives and life cycle continues. Under optimal climatic conditions, small hive beetles can complete their egg to egg life cycle within 4-6 weeks. Small hive beetles can complete 5-6 generations in a year.
Immediately after hatching from eggs, small hive beetle larvae enter into the honey comb and begin feeding on honey, pollen (collected by bees) and brood. During this feeding process they can completely destroy honey combs. In case of heavy infestation of small hive beetles, honeybee will leave the colony. In addition, both adults and larvae of small hive beetles carry yeast, Kodamaea ohmeri on their bodies into the colony (Benda et al., 2008). Once yeast is introduced in the honeybee colony, it will start growing on comb. The growing yeast will then ferment honey in the comb. This fermented honey becomes useless as food for honey bees as well as for human consumption. In addition, the compounds secreted by yeast, Kodamaea ohmeri also attracts more beetles to beehives. As described above, small hive beetles will also destroy stored honey.
Following chemical and biological options are available for beekeepers to control small hive beetles.
A few chemical insecticides such as GuardStar and Checkmite are available to kill pupae and adults of small hive beetle, respectively but the extra care is needed during and after application of these pesticides because they may be toxic to humans, pets and the environment.
Beneficial entomopathogenic nematodes can be used as biological control agents against small hive beetles because they are effective in killing mature larvae and pupae of small hive beetles. These nematodes are also commercially available and not harmful to animals, honeybee and humans. They are easy to apply using water cans or any traditional sprayers. Recently, Dr. Shapiri-Ilan (USDA scientist) and his colleagues have demonstrated that the beneficial Heterorhabditis indica nematodes can reduce the nematodes population of small hive beetles (Shapiro-Ilan et al., 2010). These researchers also reported that Heterorhabditis indica nematodes can cause over 78% mortality of small hive beetles under laboratory conditions.
Although Heterorhabditis indica nematodes were originally isolated from Southern India, they have a global distribution. Heterorhabditis indica nematode is considered as an important candidate for the biological control of many insect pests including fungus gnats, root weevils, white grubs and small hive beetles. This nematode is heat tolerant and works better against many insect pests when temperature is above 25oC. Recently, it has been demonstrated that this warm adapted nematode is effective against small hive beetles (Shapiro-Ilan et al., 2010).
The best time to apply beneficial entomopathogenic Heterorhabditis indica nematodes on the soil surface when mature larvae (grubs) of small hive beetle move into the soil for pupation. As mature larvae of small beetles generally move about 3 feet away from beehives in the soil for pupation, entomopathogenic nematodes should be applied to the soil surface within 3 feet area around honeybee hives to target and kill both mature grubs and pupae of small hive beetles. Since entomopathogenic nematodes are very sensitive to UV light, they will die within a minute or two when exposed to direct sunlight. Therefore, nematodes should be applied early in the morning or late in the evening to avoid exposure to UV light. Another advantage of applying entomopathogenic nematodes late in the evening around the beehives is that these nematodes will be ready to attack the mature grubs/larvae of small hive beetles that generally move during night time to the soil to pupate. In addition, these moving grubs will be easily found by cruiser entomopathogenic nematode like Heterorhabditis indica to attack mature larvae that are already entered in the soil at the depth of 10-20 cm to pupae and those larvae already pupated.
Beneficial entomopathogenic Heterorhabditis indica nematodes should be applied at the rate of 23000 nematodes per square feet area around each honeybee hive. This rate of application will be enough to kill over 78% mature larvae and pupae of small hive beetles.
Cabanillas, H.E. and Elzen, P.J. 2006. Infectivity of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) against the small hive beetle Aethina tumida (Coleoptera : Nitidulidae) . Journal of Apicultural Research 45: 49-50.
Ellis, J.D., Spiewok, S., Delaplane, K.S., Buchholz, S., Neumann, P. and Tedders, W.L. 2010. Susceptibility of Aethina tumida (Coleoptera: Nitidulidae) larvae and pupae to entomopathogenic nematodes. Journal of Economic Entomology. 103: 1-9.
Shapiro-Ilan, D.I., Morales-Ramos, J.A., Rojas, M.G. and Tedders, W.L. 2010. Effects of a novel entomopathogenic nematode-infected host formulation on cadaver integrity, nematode yield, and suppression of Diaprepes abbreviatus and Aethina tumida. Journal of Invertebrate Pathology. 103: 103-108.