A Breakthrough in Greenhouse Pollination

For the past fourteen months I have had a strong double-entrance beehive in a fully screened greenhouse, when conventional wisdom said it could not be done. Although success with a single hive proves nothing, it is a very encouraging start.

In the winter of 2011, my neighbour Ray Daniels of Sunray Strawberries asked me to put a hive of honeybees, Apis mellifera, in an experimental greenhouse on his strawberry farm. Ray, and the manager of a firm named Magnificent, Rudi Bartels, who specialises in horticultural harvesting technology, are running numerous trials involving strawberry cultivars in hydroponic troughs, and robotic harvesting, all within a greenhouse.

The enclosure has a system of clear plastic walls, ventilation screens of very fine insect mesh, and an exterior blind that can be moved over the ventilation screens to give a range of ventilation from open to closed. The idea is to exclude unwanted insects and obviate the use of insecticides, while allowing some degree of climate control.

Of course I told Ray that to my knowledge, at that time, no one had successfully kept a hive permanently in a greenhouse, but I had a few ideas. If a hive had a front and a rear entrance, one to the wide world and the other to the enclosure, it might survive indefinitely and do the interior pollination job. Any unwanted insect would have to run the gauntlet of the beehive to gain access to the greenhouse. Ray and Rudi thought this was an acceptable risk.

A few enquiries of Winston Lamb, who had been involved in trials at Gatton by the late Graham Kleinschmidt, of pollination by hives ‘in tents’, revealed that the limited success they had was by using four- or five-frame nucleus hives in shifts of a fortnight. The nucs were fed 50/50 sugar and water syrup, and pollen. (I'll return to this.) When the experiment ended, they had concluded that a hive ‘half in and half out of the tent’ might survive and do the job. Such an arrangement would have two obvious limitations:- first, how to keep the ‘tent’ sealed while adding or removing supers, etc; and how to exclude unwanted insects.

In a fit of lateral thinking, I made up two experimental brood boxes each with a fixed base consisting of a front-access variation of the Freeman small hive beetle trap, a full-width front entrance eight mm high, and a rear entrance of about 150 mm of 50mm diameter PVC drain pipe. The advantages of the latter include ease of "plumbing" through walls, and availability of caps for temporary closure of rear entrances.

The intention was to trial one hive inside the greenhouse with the rear entrance to the outside world, and the other hive outside the greenhouse with its rear entrance providing access to the inside of the greenhouse. A site problem has delayed deployment of the latter, but I can report that the hive inside the greenhouse has been a resounding success so far.


Photo of hive inside greenhouse. Photo courtesy Rudi Bartels

Photo of hive inside greenhouse. Photo courtesy Rudi Bartels

Details are as follows.

On 29/8/11 two strong colonies were robbed and rehoused in the two experimental hives - ten-frame full-depth brood boxes with ten frames, and one or two WSP supers of nine frames. Both had their rear entrance capped, but in hindsight the bees should be using both entrances before the hives are moved to a greenhouse.

On 20/9/11 one hive was moved to a stand in the greenhouse, so that the rear entrance was plugged into a previously mounted pipe to the outside. Unfortunately, the bees took several days to start using the rear entrance, and initially there was a huge number of dead bees on the floor for the full internal perimeter of the greenhouse. A water supply had been provided before the bees’ arrival, so it was not thirst that killed them.

Premature mortality decreased once the bees began using the rear entrance as well as the front one.

An inspection on 26/9/11 revealed no sign of a queen, two recently used queen cells and no eggs or larvae, so a caged queen was introduced on 30/9/11. When next inspected, on 5/10/11, the queen had been released.

The hive was given a once-only 750 ml booster of 50/50 sugar syrup, and the water supply was not continued.

Incomplete pollination of a strawberry flower is one of several reasons for deformed fruit. Some time after the introduction of the bees to the greenhouse, I asked Rudi whether he had done deformity counts before the bees arrived, and whether he intended to do some ‘after’ counts. He said it would be a waste of time. Why? Because before the bees came, he could not find a well formed strawberry among the thousands in the greenhouse.

At the appropriate interval after the bees came, he could not find a single deformed strawberry!

So this nailed the pollination question, but what about the bees? Rudi noticed an interesting phenomenon, and came up with the likely explanation. Bees began trying to escape the enclosure in very narrow bands along one side, but not as one might expect, in a corner. It could be that a field bee using the rear entrance (to the outside world) does the waggle dance or whatever, and the appreciative audience of field bees in the hive head out the front entrance (inside the greenhouse) in the direction indicated, but hit an impassable barrier. (A bit like Christophoro Columbus hitting America on his way to China in 1492. Things don't always go as planned.)

A brood-box inspection on 30/10/11 revealed that the hive was queenright and doing OK as distinct from well. Quick, unrecorded checks in the following months confirmed that opinion, and it was robbed of a WSP box of honey on 3/5/12. In the time taken for the greenhouse hive to produce that box of honey, hives a few hundred metres away produced two or three boxes, but it must be remembered that the hive suffered a major setback when first shifted to the greenhouse. It came through winter fairly strongly. A few checks during the strawberry season revealed a slow accumulation of honey, but by 16/11/12 it was solidly packed with honey, and at the time of writing has been undersupered ready to rob.

It remains to be seen whether this hive can succeed in naturally requeening itself. The odds favour a virgin queen flying into the enclosure and either failing to mate, or mating with her brothers. So far this hive's value as a pollinator is undoubted, and its low honey production is not surprising given the continual loss of some of its field bees due to navigational problems. To keep a hive permanently in a greenhouse it might be necessary to requeen at intervals, perhaps annually as for high-productivity migratory beekeeping. The low honey production in a commercial situation would be outweighed by the value of pollination.

We expect to be able to fit the exterior hive to the greenhouse soon, while leaving the interior hive in place. We will be able to observe whether bees are using the rear entrance of the exterior hive (into the greenhouse), so there is no question of interference between the two experiments. The question which interests me is the relative longevity of the two hives.

Meanwhile, back in the real world of greenhouse pollination, Rudi has pointed out that our situation differs from that of the large-scale glasshouse operations. We have native forest and the wildflowers of pastures and cultivations (which some people call weeds) within easy reach of the experimental greenhouse. The big operators have huge glasshouses amidst hectares of glass, sometimes in cold climates with a short foraging season for bees, with little vegetation of use to the bees. In such situations the chances of bees relying on natural resources to survive the winter would be bleak. Several solutions, or combinations of solutions, are obvious, such as artificial feeds, growing plants of high nutritional value to the bees along with the target species inside or outside the greenhouses, and either keeping the bees entirely in the glasshouses or giving them access to the outside world as well.

A great deal more is now known about bee nutrition than was the case in Kleinschmidt’s day, and it might now be feasible to keep ‘bees in tents’ by feeding modern formulations such as Bee Build and Feed Bee. Rudi is particularly keen to investigate the possibility of keeping standard beehives in glasshouses by feeding them and denying them access to the outside world. This would eliminate the continual bee losses previously mentioned, presumably caused by scouts directing field bees to floral resources outside the glasshouse, but the bees using the wrong exit from the hive.

It seems to me that if natural resources permit, the inside/outside option would be more economical, but in areas of intensive glasshouse operations, the feeding option might win out.

We would like to hear from anyone working on greenhouse/glasshouse pollination. Ray Daniels may be contacted by e-Mail ray@sunraystrawberries.com.au, Rudi Bartels rudi@agnificent.com, and myself c/o my good wife julietadman@gmail.com.

Author: John Tadman