Posts Tagged ‘Bees’
Pollination under Plastic
Last week we posted a picture showing a very large number of honeybee hives protected by an enclosure in the middle of a Chilean blueberry farm. The owner knows their value to the crop, perhaps especially for blueberries.
Some of the most frequently asked questions about growing of crops under tunnels are concerned with bees and pollination. These questions have become even more pertinent as legislation governing the use of imported bumble bees has tightened in many countries.
There are a few basic things to remember:
Bees cannot ‘see’ the polythene films used for tunnels
Honeybees waiting in hives outside don’t know what the temperature is inside tunnels
UVb light is an important steering aid for bees and other insects. Some films block more UVb than others.
Bees aren’t the only pollinating insects
Cherry blossom above a commercial bumblebee hive inside tunnels
During the summer there is normally a surplus of pollinating insects, including a great many different nectar feeding insects. It is rare to hear of fruit setting problems under tunnels that are adequately vented during the summer months. For most berry crops the best temperatures for bees coincide with those for good yields – mostly less than 25oc. Above that temperature both bees and photosysnthesis slow down significantly.
IN THE SUMMER VENTING IS IMPORTANT FOR GOOD YIELDS, POLLINATION AND FRUIT QUALITY
The danger time is in the Spring, especially when crops are being ‘forced’ to flower early. To gain temperature tunnels are kept closed. Bees kept outdoors may be shivering in their hives unaware that the tunnelled crop is warm and in open flower. In closed, permanent tunnels strawberry growers used to introduce blow flies (as pupae close to emergence) as pollinators to overcome this problem but many countries now have the luxury of bumble bee hives from commercial companies like Koppert http://www.koppert.com/pollination/. Bumble bees are active at lower temperatures than honeybees, pollinate using a ‘buzz’ method that has technical advantages for crops such as tomato and the commercially available species are less aggressive towards crop workers.
A large wild bumble bee in Argentina.
Honeybees are still used under glass for various crops – often in combination with bumblebees. The large size of hives makes this less practical for small tunnels but for large, field scale crops honeybees are worth looking at. Hives used in these situations will tend to lose bees as they waste energy attempting to fly through the sides and roof or are lost to the outdoors. Where bumble bees are not available, tunnel growers are working with honeybee hives however at the time of writing we don’t have sufficient experience to provide reliable advice on this option.
A honeybee hive inside a blueberry tunnel
IN THE SPRING DO NOT KEEP TUNNELS CLOSED DURING FLOWERING UNLESS A DAMAGING FROST IS DUE OR YOU ARE CERTAIN THAT THE NUMBER OF POLLINATING INSECTS INSIDE THE TUNNELS IS SUFFICIENT.
REMEMBER THAT, EVEN IN THE EARLY SPRING, SUNNY CONDITIONS CAN CAUSE FLOWERS TO MOVE FROM WHITE BUD TO PETAL FALL VERY QUICKLY. DON’T BEE LATE!
Bee Steering
UVb = Light in the ultra violet spectrum between the wavelengths of 315nm to 400nm
Bees do use other cues for navigation and experiments have demonstrated that bumble bees can learn to identify flowers in the absence of UV light but in general terms the impact of bees and other pollinating insects is strongly influenced by it.
When purchasing polythene films for tunnels it is worth asking for clear information about the transmission of light in the UV range. Standard Visqueen films supplied in the UK allow sufficient UVa through to facilitate the work of bees but some films, especially those formulated for use in countries with very high light levels, contain a lot more inhibitors. When these polythenes are used in dull weather or in other countries there may be problems with fruit set.
Bee Information
Mason bee shelter at a Biodynamic farm in Poland: What potential for tunnel use?
From Chile Tunnels to Wet Midlands
Where dogs fly!
Chile Tunnels
Haygrove ventured close to the Antarctic to help with a project growing Ribes in the far south of Chilean Patagonia. A wonderful bunch of INIA scientists, advisers and growers are trying to beat huge winds to produce fresh currants well outside the normal shipping season. On the flight down from Santiago Punta Arenas John Berry was told that Punta Arenas was the only place ‘were dogs fly’ and that it was necessary to have ropes along the street to assist the elderly…In the Summer! Correctly specified and with appropriate windbreaks it should be possible to build Haygrove tunnels to cope with growing conditions close to Cape Horn just as they do in the South Africa Cape region but it’s a challenge.
Wind protection required both for the tunnels and the crops
From these chilly tunnels we visited cherry and raspberry growers in the Central Plain before looking at an exceptional blueberry project north of Santiago. A very high standard of technical management at the farm has resulted in very early blueberry production on the foothills of the Andes with Haygrove tunnels providing additional earliness together with protection from both frost and wind.
Early blueberries, north of Santiago
A big thank you to our hosts and everyone who helped us! You are setting very high standards of hospitality and horticulture – even for bees which is a subject to be discussed later…..
Catering for honeybees
Wet Midlands
Back home in England the West Midlands hasn’t been dry for weeks. Famously Cumbria, 200 miles north of here, recorded 372mm in 24 hours. Ledbury hasn’t been that wet but many growers have been pleased that modern tunnel designs have allowed them to keep covers on over peat and coir grown crops during this difficult time. Telescopic and Solo tunnels have been OK during a series of November storms. Raspberries were still picking in un-heated glass last week but most growers are now concentrating on preparations for 2010.
Waiting for Summer to return