What was it all about?

Beginning in 2016, this five-year project analysed the role honey bees and other native pollinators (native bees and other insects) have in pollinating crops under field conditions. The global decline of insect pollinators threatens productivity in cropping systems. The honey bee in particular plays a key role for Australian horticulture, but is expected to decline severely if the Varroa mite establishes. The project also researched key factors that may limit the persistence of wild pollinator populations in agroecosystems.

The project team addressed these objectives through targeted research conducted in apple and cherry orchards as well as grower engagement aimed at achieving five objectives:

• Identify pollinator species present on farms and determine which of these visit and pollinate different horticultural crops in field situations
• Determine how bees use different floral resources across seasons and devise and test appropriate farm-level floral enhancement schemes
• Test experimentally manipulated climate change effects on the timing, quality and quantity of nectar and pollen available to bees in key forage plants
• Determine what microbial diseases infect insects in Australian pollinator communities and which of these are shared across native and honey bee populations
• Inform and educate growers and land managers about bee population health.

The team confirmed a major role for honey bees in apple and cherry orchards, and that they are the only significant pollinator in almonds.

With the role of wild honey bees versus rented hive bees unknown, a farm-level marking and survey investigation was developed. It found some native bees are equal or better pollinators at an individual insect level but occur in lower numbers. Wild stingless bees were an exception, which could be abundant when present and may already play a major pollination role. Resilience could be provided by other native bees if honey bees collapsed, with land management greatly influencing numbers.

Pollinators require non-crop floral food resources, especially in production systems where the main crop has a short bloom period. The team found that the diversity of pollinators and/or crop visitation by pollinators increased with the diversity of non-crop floral resources.

A selection of native plants were screened for nectar production and flowering phenology, with native perennial plants found to be a good option to support resident pollinators year-round. Commercially available exotic annual plant seed mixes may provide nectar and pollen resources to attract greater honey bee numbers during crop bloom.

Ongoing experiments were leveraged to investigate climate change influences on plants / pollinators. Over three flowering events, results showed that elevated CO₂ did not significantly change the nectar of Eucalyptus tereticornis trees, but that honey bee numbers were consistently lower in these conditions. In warming experiments, plant responses were highly variable between the 10 species studied, making generalisation difficult, although changes in flowering phenology were noted.

The main viruses associated with honey bees in Australia were all detected in the apple and cherry orchards, with black queen cell virus the most common. Most viruses were also detected in native pollinators, but were far less prevalent and it is not yet clear if they cause symptomatic diseases.

No major new insect-specific viruses were detected in native pollinators, however honey bees and native pollinators may potentially vector some significant plant viruses, notably apple stem grooving virus.

To engage growers, several workshops and field days were held, with fact sheets, industry magazine articles, podcasts and videos also shared. A grower study tour of India focused on crop pollination issues was organised, with links established during the tour leading to parallel collaborative research.

ACT NOW

The project team released three factsheets and a guide for use by industry:

• Bee biodiversity: Safeguards for pollination services
• Are honeybee diseases shared amongst Australian pollinators?
• Encouraging wild pollinators to your orchard
• Powerful pollinators guide