Acotanc: Bee Tubes in Fruit pollination

Bee Tubes in Fruit pollination

Author: Rob Manning
Research Officer
E-mail: [email protected]
Organization: Agriculture Western Australia
3 Baron-Hay Court
South Perth WA 6151
Phone: +61 8-93683567 +61 8-94742479
E-mail: [email protected]

Bees kept in cardboard tubes are a new development for orchard pollination which solves some orchard problems.

I will run through what we have done with these things. The tube itself has won a few awards. It won an award at Karragullen in ‘97, state government award about ‘96, and an award in Canada last year. It is mainly set up for people who have high density orchards where they plant with trellising, or on remote stations. To get bee hives there to put on their rockmelon or watermelon crops is expensive and difficult. It is easier to send them a package of bees they can use for about 10 weeks or so and then dispose of them when they have finished pollinating.

Some of the beekeepers who have used them have modified them a little bit. These have been wax-dipped so they are a little more waterproof. It adds to the cost, but this fellow was doing quite well with them. This is what I mean by high density orchards. The trees trellised into one single plane offer barriers to the feral bees from the forests. Some of the rows are too long for honeybees to penetrate very deeply. Some growers haven't left enough room for bee hives in groups, and the method of putting single bee hives in the rows is very time consuming. If you have big orchards, you can't fit big trucks down the rows, which makes it difficult to carry out pollination effectively.

With the tubes, bee densities in orchards can be manipulated. You might be in a forest situation where there is a high density of feral bees, or you might have a commercial beekeeper delivering hives for pollination, and what happens is the bees, at distance, when they are away from orchards too far, show a steady decline in numbers penetrating the orchards. Once bee numbers are down in orchards, yield drops. If you can manipulate the bee density to reasonably high levels in the orchard by putting in disposable hives or other methods of getting bees or insects into your orchards, there is a steady increase of yield, which is what the grower is always looking for.

One thing about apples, once the pollen germinates, it forms a pollen tube that goes into the ovule and forms a seed. The more seeds you get in apples, the higher the calcium content which gives the apple a higher ability to be cold-stored, to give a longer shelf life in the supermarket. With the lower calcium content, there is a fruit disorder that makes the fruit go brown inside, especially during cold storage.

In Japanese plums, a common variety, as you get more insects into an orchard, yield goes from about 22 kg per tree up to about 30 kg, just by increasing the pollinating insects. One way of doing it is to use some sort of disposable pollinating system. These plums are growing on trellising in high density orchards. There are many types of trellising used in orchards.

Up in the north of Western Australia, where we use these tubes in melons and curcubit crops, which are grown in big, long rows; the longer the row and the longer the distance from the bees, the less yield you get, because the percentage of foragers decreases over distance. After about 500 metres the bees on this crop are down to about less than 10%. With many of these curcubit crops, eg rockmelons, water melons, pumpkin, because they have so many seeds, the flowers need a lot of pollen. Each pollen grain forms a seed. You need that seed development to form the actual size of the fruit. If you have less than 400 seeds in a rockmelon, you won't get a commercial-sized rockmelon. A lot of research shows that if you get about 8 bees visiting every flower, you will have a successful commercial crop.

Beetubes are made out of cardboard and hold about a kilo of bees, plus the queen bee. They have to actually build their own comb in there. You feed them sugar syrup or honey to get them established. In about 4 weeks they have the comb established, and then a huge volume of pollen starts coming in to feed all their young.

We experimented with this tube, just to make sure that it worked. We set up an experiment in a cherry orchard where we had Tatura trellising,, the varieties used were Van and Bing. In order to get the distance between the rows, to separate experimental treatments so we could manipulate the bee density in each of the rows, we actually bulldozed one row of cherries in every second row. In this particular row we used 3 tubes. Another row we used none. This zero bee tube row was in the middle of the rows where we put bee tubes in. The other row at the other end had 8 tubes so it had quite high density. There were pollinator trees (Bing) every third tree, so the insect shift of pollen between the two varieties was quite good. This is essential to get the yield of cherries.

Then we monitored what the bee densities were doing. This is the 8 tube row; it is just a wall of flowers. When you have the bees in there they move up and down the face of flowers on the trellis. When you look down the next row, the bee penetration across rows is not great. In some years it is, and depends on the weather. On an overcast or wet day the bees stay fairly close.

This is the feral bee population before we started, a year later. We were getting less than 2 bees per tree. An orchardist won't get an economic yield off the trees with that. When you put the bee tubes in, you can get the density up around 10 or 11 bees per tree, which is about what you need for a commercial crop.

In the zero bee tube row, you see only a few of the flowers produce fruit. Essentially, it was a very poor yield. That is what you would see in an orchard that has very low bee activity. Subsequently, the tree yield in December was just a smattering of good-sized fruit.

In the 8 tube row, you can see a lot more flowers are pollinated, and you can see it in the harvest in December where there is a lot more fruit. These trees were running at an average of about 30 kg per tree, whereas the trees in the centre, where there were no bees, were running at about half that. About half, or 15 kg, would be of export size.

This is an illustration of what happens with the bee densities. This is the basic export size of cherries: anything bigger than that is exported, anything smaller, the exporters don't want. You see where there are high densities of bees about half the fruit are big. The trees in the centre row produced less fruit, but there was an increase in fruit size so that essentially the whole 18 kg yield is export size. When we got to the 3 tube row, we were averaging 32 kg per tree. We also had a much higher number of cherries that moved into the export range, compared to the 8 tube row. In this experiment, the 3 tube density was about the best in that situation. It just illustrates that manipulation of basic, simple bee densities in an orchard can have some dramatic results in yield. That is what orchardists are looking for in their income.

When we first started this experiment, the trees in the orchard were 7 years old. We hadn't had any bee hives in the orchard and consequently we had low yields. From 1993 to about1995 we brought some bee hives in, and we had mixed yields, up and down, because the hives had to be placed some distance away from the orchard. If it is raining or overcast, bees will only fly when it exceeds about 12.6 degrees. Anything less than that, they generally don't forage. This variable yield here is because the hives were situated away from the orchard. We think the weather had a big effect on the bees.

In 1996 and 1997, two years in a row, we had bee tubes in the orchard and both years we had pretty good yields, quite consistent yields. Some people said the yields were up because the trees were getting older. This is year 14 out here: we took the bee tubes away and just relied on the feral bees. In that year, '98, the yield fell back to 10 kg on average, from roughly about 30 kg. So it is quite a big difference. That demonstrated that the bee tubes were actually working and doing their job, it wasn't a tree age effect.

Because of the differences in distance, this one is the 8 tube row, the cherries were more mature more quickly. This one was the centre row, only 30 feet away, with no tubes in it. You see there is quite a difference in maturity of the fruits. Because of this, we felt that there was some application in which you could use bee tubes to muck around with the dates of picking, and therefore orchardists could have have their workers working different days to do all this instead of having them all there all the time. You could actually stagger the bee tubes and have the fruit maturing on different days, so it was a little fresher when it was picked.

These are the frames of brood the bees build in these tubes. Each cell contains an egg the queen bee lays, that develops into a larva. Larvae must have pollen. They must have protein, which the bees eat. They have little glands in their heads that make royal jelly out of the protein in pollen, called worker jelly in this case. They are feeding worker bees. There is a continuous cycle of bee breeding. To produce those sorts of numbers of bees you need a lot of pollen. When the bees go into orchards, they really have to hammer the trees to get pollen to survive. That is basically why the tube works. It puts the bees into an artificial swarming mode, where they actually have to survive. To survive, they have to work hard. Sometimes they work themselves to death in about 10 days.

Each bee hive maintains itself at 35 degrees, so it is fairly warm inside a hive, especially if it is cold outside. They have to burn a lot of carbohydrate (from nectar) to generate heat. The orchard trees don't produce a lot of nectar, so they run out of nectar and they run out of heat and the colony of bees collapses.

It is typical of the way comb gets built. You can rip the red lids off and look inside. This has been blown with a bit of smoke to clear away the bees, so you can see the comb.

Q. What do you do with the hives if you are spraying with insecticides?
A. We hang them up in the orchards. They have a hook we use to hang them on the trellising. We just get a garbage bag, slip in over and pull tight. Then the sprayers can come through in the evening, about 4 or 5 o'clock. We get them to use lower toxicity sprays, maybe six hour. Then the following morning, the bags get pulled off and they are away again. They have to be released before the sun comes up or they will get too hot. There is no loss this way. Whereas, with bee hives you have to actually remove or cover them.

This is what I mean about 'excluders.' When the bees squeeze past each other, each bee has a heap of pollen on it, coming in from the orchards. As they move backwards and forwards through here, the body hairs will mix the pollen up. The pollen coming in gets mixed with the pollen coming out. The black plastic here has a positive charge that it picks up from the bee movement. A lot of the pollen sticks to the edges of the plastic and gets mixed around by the bees. This is its purpose.

Because there are so many bees milling around, bringing in lots of pollen, the pollen gets knocked off their legs and you will see bits and pieces on the ground here. A lot of experiments show that if you remove the pollen from the bee the inside of the hive gets more and more short of pollen. More and more of the bees that go to collect nectar get changed over to foragers for pollen, so it actually increases the pollen yield, and increases the effectiveness of the bees in the orchard.

Here is another plum orchard. You can see bees flying around the six tubes here. You can go to the next bay and see a few, and then in the next bay there is nothing. These new man-made structures in orchards are almost like barriers to bees coming in. So if there are hives situated in front, the penetration isn't very good. In Europe they find there is a huge depression in yield in the centre of orchards. They lose lots of money on it. You could actually run lines like old fashioned washing lines that can be raised and lowered. You can hang the bees on that and raise them up so they are flying above the trees.

We have used them in avocados. After a period you get quite a build-up of the bee population, so you have all these bees to feed and they chase the pollen.

These are rockmelon crops up in the north west of Australia we pollinate with the tubes. A lot of this stuff is planted in rows a few weeks apart, so there are always plants coming on. Once the rows have been picked they are hoed in and the next row comes on stream. The bees have to be kept moving from row to row. We can keep bees in a 5 degree cold room for about six days, provided they have a fair bit of honey in with them. Most of the growers have cold rooms. They can take the bees out and put them into the next row when they need them.

We pioneered a delivery system of bees in chiller trucks at 5 degrees C. We have taken them from Perth all the way to Broome, Derby, and Kununurra. We could take them anywhere in Australia by that method.

This is the first batch we sent up, just a little batch of three, all wired up, a test run into a rockmelon crop at Broome. You can deliver quite a few in a ute which can fit down a row in this high density orchard, whereas some of the trucks can't get in, can't deliver the bees, and have to put them away from the orchard, which defeats the purpose. In a lot of orchards now, you will see bird netting. A lot of trucks can't fit under the bird netting, and the bees can't go in, so these have to go underneath. Beetubes are more effective than the traditional bee hive. They are a lot easier to use.

Q. Does putting bees in an orchard keep other insects away?
A. I have noticed that putting bees in an orchard seems to generate a lot of insect activity, especially hoverflies. It has been demonstrated that once you have removed nectar out of a flower, the flower actually secretes more. So over a period of 5 days that a flower is open, if you keep taking nectar out, it keeps pumping out more and more. Nectar is the attractant for its pollination system, for the plant to survive, keep evolving.

The other thing, when you have tubes in these sorts of trellis orchards, when there is a lot of background weeds, capeweed or radish, for instance, these plants are more attractive than plum flower. The nectar and pollen in these plants differ. The oil content of pollen from the capeweed and radish is much greater than the oil content of plum flower pollen, and the bees can prefer the high oil content pollen. If you haven't got all this mowed down, you have got Buckley's of keeping the bees on the target crop.

I was going to explain that normal bees in hives do have a disease called American Foulbrood, a bacteria that affects the larvae. It is quite a persistent disease because it forms spores. Everywhere in Australia there is a Beekeeper's Act that is quite specific about this American Foulbrood disease. Rules and regulations about where you shift bees and quarantine because of this disease. But, because we are wanting to shake a lot of bees into these tubes the industry was concerned that we would spread this disease around and affect them. In the beekeeping world honey samples are tested in the agricultural labs and the spores germinated on a special agar plate, which tells anybody looking at the agar plate how infected the honey is with American Brood disease.

So, we did some experiments where we shook fairly heavily diseased bees into tubes and maintained them for sixty days, which is long enough for them to be used in pollination. Pollination of cherries and almonds occurs in 10 days, so there is a fair bit of leeway there. It was just to show the beekeeping industry that this was a reasonably risk-free method even if we happened to shake some diseased bees out of a hive. Therefore we wouldn't be spreading disease. The infection dropped down to almost zero after 60 days when we tested the honey in these tubes. Diseased bees have spores on their bodies and in their guts. So, what it means is that when we sampled the bees sixty days later, all the spores that had been there previously, had presumably been locked up in the wax they built. The bees have wax glands under their abdomens and they convert the honey they eat into wax. Their systems are purged of spores.

Last year, we were looking at something a bit bigger, for some of the cooler climates such as Victoria. Bees in buckets have been developed in a similar system, except now these can be filled with two litres of sugar syrup to keep the bees going in terms of generating heat in the cold weather. Being active enough to pollinate during the ten or so days they are needed in the almond orchards. It is just another way of getting bees cheaply to an orchard to do the job.

Another reason for beetubes is that people involved in food have all these new rules to follow in health and safety, food quality. Because, traditionally, all the hives that were honey-producing hives went into orchards when beekeeper opportunistically used them to pollinate, there have been some instances where honey was contaminated with chemicals the orchardists used. If that is detected going into our export honey market, the export market can be ruined. So we try to shake the bees out of these hives into special containers that are just used for pollination, and then are destroyed after use.

We are still trying to push the beekeepers down the track of taking the honey hives out of the orchards and using something different. It is perhaps a new business proposition for them. Something that may make them more profitable.

Q. What happens if there isn't enough pollen?
A. The bees will starve if we don't give them supplementary feedstuff. A lot of research has gone into it; there are a lot of artificial feeds you can make up that contain pollen that has been collected by beekeepers. It is mixed with high-protein stuff like soy flour or yeast, and that is blended into a patty and fed back into the hives and the bees eat it. It contains their protein, and it maintains the young bees, just for the short interval that you might need before you go onto another crop.

Q. Do you take bees to warm places like Carnarvon?
A. Yes, we take bees up there. There are low-chill plum orchards there on trellis. We have sent them to Kununurra which is probably the hottest place.

Q. Neem trees have a seven-week flowering period in January-February. Neem makes good honey.
A. Yes, you would have to migrate the bees after that, they could probably go onto Wandoo, which starts January, February. Powderbark, which is up in the hills, and that will follow into the Marri, in February, March.

Q. Are any commercial honey producers looking at bee tubes? A. There is not enough honey in them to be worth doing it that way. There are about six beekeepers going into bee tubes, one is quite large. Beekeepers won't deliver hives to people who only want about six, because it is not economic, so they switch them on to tubes which they pick up. We have had people come in and pick them up and drive away home, as long as the air conditioning is on to keep them cool.