Researchers crack small hive beetle genome

The breakthrough should help scientists develop targeted control methods and more efficient insecticidal treatments

Scientists at the U.S. Department of Agriculture’s Agricultural Research Service have deciphered the genome of a serious threat to honeybees.

Small hive beetles are five to seven millimetres long, oval and dark-brown or black in colour with distinct club-shaped antennae. They eat everything in a bee colony, including pollen, brood, honey, combs, and dead adult bees.

The pests lay their eggs in the hive and the larvae feed until they leave the colony to pupate, only to re-infest a hive as an adult. They can cause honey to ferment and, if the number of beetles is high enough, adult bees will abandon the hive.

There are few effective treatments to rid hives of beetles.

The small hive beetle is native to sub-Saharan Africa and first arrived in the United States from South Africa via shipments of fruit to Florida or Georgia in 1996. In 1998, the beetle was blamed for losses of more than 20,000 honey bee colonies in Florida alone.

Since then, it has spread rapidly by transport of infested colonies for pollination services and shipment of packaged bees.

The beetle turned up in Ontario and Quebec in 2010 and in New Brunswick in 2017 as a result of hives imported from Ontario. It is now found on all continents except Antarctica and is an economically devastating parasite of honeybees, bumblebees and stingless bees.

However, with the beetle’s genome decoded, the new information should provide important information to develop targeted control methods and more efficient insecticidal treatments.

The genome material has already indicated how the beetle finds beehives and what pheromones or scents it follows to target colonies.

“There are two ways,” said Jay Evans, research leader with ARS. “They smell out the bees themselves or they seem to smell out a fungus (kodamaea) that is associated with bee hives. But, regardless, they likely orient via smells that they perceive through targeted cells in their antennae.”

What makes the small hive beetle so hard to control is its strong gene-guided system that allows it to detoxify insecticides.

“Beetles in general eat from a lot of plants that are well defended against them,” said Evans “(The plants) use hairs, thick skin cells, and chemicals. It is thought that this leads beetles to evolve stronger abilities to detoxify chemicals, including agro-chemicals.”

The newly deciphered genome will allow researchers to get a better understanding of these detoxification genes, and the pest control industry is already working on applications based on the new information.

“They are actively working on using some of the genetic insights for techniques like RNA interference, as are two university labs I know of,” said Evans. “This would be one way of control along with exploiting genome insights into the smell receptors of beetles to help refine effective baits for luring beetles in.”

In the report, Evans wrote that unique detoxification pathways can help identify which treatments might control the small hive beetle even in the presence of honeybees, which are notoriously sensitive to pesticides. The beetles are also known to develop in bumblebee colonies.

The small hive beetle is a close relative of the destructive Asian longhorned beetle, a wood-boring beetle that attacks healthy hardwood trees, such as maple, elm, poplar and willow. It is also a close relative to other sap beetles that are pests of fruit and vegetable crops.

Insights into the small hive beetle’s genome and its associated fungi and bacteria may help develop effective controls for closely related species.

Despite the fact that there are about 350,000 beetle species and subspecies, only seven beetle genomes have been deciphered and published.

The report, titled “Genome of the Small Hive Beetle (Aethina tumida, Coleoptera: Nitidulidae), a Worldwide Parasite of Social Bee Colonies, provides Insights into Detoxification and Herbivory,” appeared in the December 2018 journal GigaScience.

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