Gorse a loved and loathed weed

Profitability of a multimillion-dollar industry in the rural sector could be jeopardised by the destruction of a loathed weed.

Beekeeping is the industry - and gorse the weed.

A meeting between the Bay of Plenty branch of the National Beekeepers' Association and Bay of Plenty regional council - called because beekeepers wanted to raise awareness of the importance of gorse to beehives - has highlighted the role played by the pest plant in bringing hives up to pollination standard in spring.

Beekeeper David Black said about 20 per cent of New Zealand's honey was produced by beekeepers in the Bay of Plenty.

As well, pollination contracts in the region earned between $8 million and $9 million a year for the beekeeping industry and were worth considerably more to the region's kiwifruit and avocado orchardists in terms of increased production.

"To meet these contracts beekeepers have to manage their honeybee colonies so as to produce a hive to a recognised standard, with bees, brood and food stores present in appropriate quantities," Mr Black said.

In winter the bee colonies are small and so they must be given sufficient time to grow, and there needs to be sufficient forage available to sustain that growth.

"An essential component for any animal's growth is protein, and for honeybees this is delivered as pollen gathered from flowering plants such as gorse," he said.

Given good pollen sources, a colony will take about two months to grow big enough to be an effective pollination unit.

Crops in the Bay of Plenty requiring pollination on a commercial scale flower fairly early in the honeybee's natural growth cycle.

Depending on weather, avocado begins flowering in September and green kiwifruit in November. Gold kiwifruit flowering usually occurs about the second week of October.

Throughout August and September, beekeepers must ensure their colonies are within range of an abundant source of pollen if they are to be ready to work those crops and achieve growers' optimum fruit standards.

No native New Zealand plants are adapted to be a workable source of pollen this early in the year. Rangiora (Brachyglottis repanda) or five finger (Neopanax) may provide bees with an opportunity in certain areas for a limited time but the flowers are generally too late and too short-lived to be of any real use.

Introduced species such as willow, gorse, alder, and buttercup are important pollen sources for bees. By far the most important is gorse - in flower for several months and widespread in many areas.

European gorse - scientifically known as Ulex europaeus - is a plant species classified as a pest in Environment Bay of Plenty's Regional Pest Management Strategy (Biosecurity Act) and is subject to various control measures.

Landowners have to destroy it whenever it is growing within 10 metres of a property boundary.

Gorse cannot be sold or propagated and so far eight insects have been released as biological controls for the plant. "Gorse is widely disliked," Mr Black said. "But besides its pivotal role for beekeepers, gorse has many excellent qualities which seem to render its labelling as a pest a little unfair.

"It is a fine nurse plant, promoting the regeneration of native bush tree species and it provides a niche for small birds.

"As a leguminous plant it is an effective nitrogen fixer, improving soil's fertility, especially that of marginal, exhausted land, which is its natural habitat."

A more recently recognised product of the hives, bee pollen, is becoming an important commodity. With its long flowering period - twice a year in New Zealand - gorse forms an important proportion of the pollen harvested for therapeutic purposes.

"There is already acute competition for early pollen forage in the Bay of Plenty. If this is to increase in line with current forecasts there is some doubt there will be enough forage available," Mr Black said.

"A strategy which is determined to eliminate one of the area's most important forage plants should not be maintained."

Buy Mr Black was worried that it might already be too late.

"Without gorse, it will be difficult and costly to produce hives in the strength and numbers the horticultural industry needs.

"The next time the region's pest control strategy is to be considered, a new tolerance for a valuable species should be promoted.

"In the meantime - where they can - landowners need to make a positive effort to use odd blocks of ground to plant bee-friendly trees and shrubs."

Friend and foe

European gorse is a pest in many parts of New Zealand and subject to various control measures.

Gorse cannot be sold or propagated and so far eight insects have been released as biological controls for the plant.

But its flowers are invaluable for beekeepers, and the plant helps the regeneration of native tree species, provides a niche for small birds and improves soil fertility.

- NZPA