Protecting our PollinatorsIndustry Best Practice
Two stand-out sessions at APAL’s November R&D Update featuring The University of Adelaide’s Dr Katja Hogendoorn and Plant & Food Research Australia’s Dr Lisa Evans provided growers with vital advice on how to build a resilient industry through optimising crop pollination. Across three sessions, these experts provided the following tips.
Understand the diversity of pollinators and regional differences
Evans, who has spent the majority of her time in New Zealand researching bee populations and the kiwifruit industry, says that the diversity of pollinators in Australia is “incredible”, with over 1500 native bee species. There are only 27 in New Zealand. “It’s mind-blowing, but also quite tricky for researchers to identify and quantify so many species”, she said. “The variation between regions is extreme.” For example, while the honeybee is the primary pollinator for avocados in New Zealand, bees in the Tri-State Murray region will ignore avocados because citrus flowers at the same time, leaving the job of pollination to flies. “Understanding regional differences (such as different nesting conditions) will help growers manage their pollination”, Evans said.
Hogendoorn commented that diversity enhances pollination, while a reliance on a single species is dangerous: “We know that from the Irish potato famine”, she said. Diversity of pollinators increases movement of insects and promotes cross-pollination in apples.
Plant or preserve native vegetation to support bees
Hogendoorn has conducted research into how much native vegetation growers need around their orchard and how it relates to the number of seeds in apples, pollinated by honeybee and native bee populations. The ideal percentage (called the “Goldilocks number”) is to have 20 to 30 per cent native vegetation in or around the orchard. Interestingly, having a higher coverage than 30 per cent leads to poorer results: “Maybe they’re distracted”, Hogendoorn said.
Relying on apple flowers to feed bees is not enough. We need to plant for bees year-round, with Hogendoorn recommending plantings of bee-friendly vegetation under trees, in hedgerows or dedicated areas near the orchard. Advice on design plantings to support bees will soon be available through PIRSA, Trees for Life and industry websites. Plant lists will be region-specific to accommodate regional differences in pollinator species.
Be aware of the effect of netting on bee populations
Evan’s study of netted kiwifruit orchards in New Zealand found, alarmingly, that 71 per cent of bees failed to return to their colony after visiting a covered orchard, while only 37 per cent failed to return with open orchards. Foraging trips per day and average days spent foraging also decreased dramatically. “The colonies were weaker after the kiwifruit season due to netting”, she said. Colonies were losing bees and were not providing the pollination service required. In New Zealand, this led to beekeepers increasing their fees to $600 per hive for 12 days during the critical Manuka season.
Evans found that adult bees fare better with roof-only netting, or roof and partial sides. If full netting is used, she recommended rolling up the sides of the enclosures during local flowering periods to let resident bees out or they’ll have nothing to eat after the orchard flowers. Putting the sides up will allow other pollinators access, including native bees and other beneficial insects that provide biocontrol.
Netting may also change the way we organise and place hives, with research indicating the textbook guide of six to eight frames per hive may be too high. Growers may also need to lessen the number of days hives are kept in an orchard as more days equals a greater decline in bee numbers.
Evans and her team experimented with mitigation strategies including:
- Putting holes in netting to allow bees access/egress.
- Providing visual landmarks for bees so they do not become lost or disorientated.
- Decreasing colony sizes (with every additional frame of bees Evans found a four per cent decrease in numbers).
Establish a good relationship with your beekeepers before Varroa arrives
At present, much of the pollination that goes on in orchards is done for free by native bee populations. But Hogendoorn warns that the feral population is about to be wiped out with the imminent arrival in Australia of Varroa destructor, a parasitic mite that attacks and feeds on Apis cerana and Apis mellifera honeybees. With the feral population destroyed, growers will have to turn to managed hives. When managed hives are suddenly in high demand, two things may happen:
- Beekeepers may put their prices up by more than 300 per cent.
- Beekeepers may not want to put their hives under nets any more as it kills too many bees.
It’s a good idea, therefore, to establish a positive relationship with your local bee people before the crisis arrives in the form of Varroa destructor.
Be mindful when spraying before or during pollination
While spraying typically takes place before bees go into an orchard, there is some evidence that spray residues don’t break down easily under netting. Hogendoorn comments: “You’ve got to be aware of the honeybee. It would be good if you don’t spray during flowering. Get to know which pesticides are friendly to bees, spray fungicides at night, and be aware that mixing fungicides may have a stronger cumulative effect than the individual effect of each product.” Keep in mind also that systemic insecticides will still be in effect even if sprayed before bees are active.