Bees busted by varroa, natives carry on

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This native bee from the genus Leioproctus is capable of carrying pollen loads similar to that of the honey bee. It is regularly seen working on onion seed crops and also on kiwifruit. Photograph by Robert Lamberts, Crop & Food Research.

Bees busted by varroa but natives and other pollinators carry on

Scientists are hoping they will be able to offer good news to arable farmers who face increased pollination costs due to the incursion of the varroa mite.

Research into native pollinators and other lesser known pollinators has shown they may be more efficient at pollinating crops than originally thought. Unlike honey bees, native bees and flies are not susceptible to varroa and their importance to agriculture, although small, may increase significantly, particularly in view of an expected 25% reduction in commercial hives in the South Island.

Crop & Food Research and the Foundation for Arable Research are optimistic further study will give growers vital clues about increasing their local populations of native pollinators.

Dr Brad Howlett of Crop & Food Research has already identified a significant number of native and other unmanaged pollinators visiting crops.

“Up until I started investigating these insects under a project funded by the Foundation for Research Science and Technology, there was very little on what else, other than honey bees, pollinated seed crops like onions, brassica and carrots. In two years we’ve established that there is a diverse array of insects visiting these crops and in many instances, they are quite common across the crops. Better still, some of them are carrying high pollen loads and move quickly between flowers.

“What we now want to establish is why sometimes these pollinators are abundant across one field but not another. We think a lot of it has to do with proximity to their preferred nesting places, places to shelter and breed, and the timing of flowering.”

Dr Howlett says it may even be feasible to develop artificial ways to increase the abundance of these pollinators, such as developing artificial nesting environments or by doing something as simple as increasing the amount of nearby hedgerow.

Meantime, Nick Pyke, Chief Executive for the Foundation for Arable Research (FAR), says growers can take some immediate action as a result of the establishment of varroa in the South Island.

“Arable growers need to act now if they want to minimise the impact that varroa could have on their business. They need to review the procedures that they currently use on farm when applying agrichemicals or irrigation to ensure that they refrain from harming pollinators in and around their property, including the mowing of sward and flowering of weeds before applying agrichemicals.”

Mr Pyke says growers could also start to familiarise themselves with indigenous pollinators and other pollinators on their farms and look at developing plans to encourage these species.

“It is also important that growers maintain good relationships with their beekeepers and continue to communicate with them regarding their pollination requirements. It is without a doubt that varroa will have a marked impact on the pollination of crops, therefore FAR will continue to provide research and extension in this area to assist with minimising the impact that the arable farming industry may face.”

About Varroa

Varroa (Varroa destructor) is an external parasite of honey bees. Adult female mites are fairly large – about 1.1 x 1.6mm. They have a hard reddish to dark brown body that is flattened and oval in shape.

Varroa mites are transferred to new bee colonies on adult bees. The mite will then leave the bee and crawl into a brood cell. Once in the cell the mite submerges itself into the larval food at the bottom of the cell and begin feeding on the prepupa. The mite will then lay its eggs. The eggs hatch and go through two juvenile stages before becoming adults. The adult mites then leave the cell when the bee emerges. The feeding of the mite weakens the hive and can cause hive failure if control measures are not implemented.

A number of other insects can pollinate flowers and could be important pollinators of crops including bumble bees, leaf cutter bees, native solitary bees and a number of species of flies. None of these species are susceptible to varroa. However, generally these species have not been managed for pollination of field crops and we are still learning about their ecology.

ENDS

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