Rent-a-Bee

Almonds | Apricots, Peaches and Nectarines | Canola | Clover | Cucurbits | Faba Beans | Kiwifruit | Lucerne | Lupins | Plums and Prunes | Pome Fruits | Sweet Cherries | Other

Almonds

A high population of honeybees is essential during almond flowering for a crop of nuts to be set. In fact, commercial almond production is not possible without honeybee pollination. For nuts to be set, a cultivar must receive pollen from a compatible polliniser cultivar. This transfer of pollen is known as ‘cross-pollination’ and honeybees are well suited to perform this task as they forage for nectar and pollen.

Almonds flower early in late winter and spring when honeybee colonies under natural conditions have a relatively low population of adult bees. Beekeepers who provide honeybee pollination services to almond growers commence preparation of their colonies in the preceding autumn to ensure each colony has a satisfactory population of adult bees available to visit the flowers and provide the best pollination result.

The main crop cultivar and polliniser cultivar are usually planted in adjacent rows. A high population of bees in the orchard will encourage foragers to move from row to row rather than along rows and this results in a high rate of cross-pollination and set of nuts. Use of a lower colony stocking rate than that currently recommended will probably not achieve this desired result.

Hives are best placed in groups, situated about 300-400 metres apart so that no tree is more than 150-200m from a hive. This is because the cool weather conditions at this time of the year can restrict honeybee flight to short distances from the hive. Groups of hives are normally placed around the edge of blocks and also in the centre of large blocks. Hives should preferably face north to north-east and be positioned in weed free, sunny positions away from the shade of almond and other trees.

Almond flowers are best pollinated as soon as possible on the day they open. Delays in pollination after this time can result in a much lower rate of set and research has shown that little if any set occurs if pollination is delayed by five days or more. For this reason, delays in hive introduction to this crop should be avoided and careful distribution of hives, as described above, should be followed so that all trees are visited by bees whenever bee flight s possible.

Leaving pollination of almond orchards to feral honeybees is poor management because their numbers are too low and they cannot be distributed throughout the orchard.

 

Apricots, Peaches and Nectarines

A number of apricot cultivars, particularly some of the newer lines, are self-infertile and require cross-pollination from another compatible cultivar to set a commercial crop. A degree of incompatibility also occurs between some cultivars. Care must be taken to determine the pollination requirements of specific cultivars before planting trees and where necessary allowance must be made for an adequate number of polliniser trees for cross-pollination of the main crop cultivar.

Trials in Victoria have shown a high degree of self-pollination in the cultivar ‘Trevatt’. Honeybees can improve the set of self-pollinating cultivars where it is desirable to increase the crop load. Where cross-pollination is required, the introduction of honeybee colonies will help to ensure a good set.

Peaches and nectarines are considered to be self-fertile and self-pollinating. This means that cross-pollination and honeybees are not usually required for an adequate crop to be set. However, honeybees readily forage on peach and nectarine blossom and can be used to increase fruit set in situations where the set is low. Bees have also been successfully used to increase the set of peaches grown in greenhouses.

When planning an orchard, it is advisable to seek advice on the pollination requirement of specific cultivars of these stone fruits from a fruit tree nurseryman.

Growers have two choices to obtain pollination

Ensure adequate numbers of bees are evenly distributed throughout the crop by using honeybee crop pollination services provided by beekeepers on a fee-for-service basis.

Leave pollination to feral honeybees. This is risky because there may not be enough feral bees in the immediate area. Their numbers may fluctuate from season to season as a result of disease, pesticides and drought. The location of their nests usually results in poor distribution of bees throughout the crop. Bees on your neighbour's property will most likely be too distant to provide you with optimum pollination.

 

Canola

Cultivars of canola (Brassica napus) are largely self fertile and self-pollinating. Self-pollination occurs when pollen is transferred from the anthers to the stigmas of the same flower. Research has shown that this crop is generally 75% self-pollinated and for some cultivars this figure may be as high as 88%. Wind can provide some pollination either by causing self-pollination through movement of the plants or cross-pollination when pollen is blown from one plant to another.

Canola is very attractive to honeybees. The nectar usually has a high sugar content and in many cases, strong honeybee colonies will store some honey although this may vary according to district and cultivar grown. Some apiarists have found nectar yields to vary from district to district. Observations by apiarists indicate that less honey is produced from canola in crops grown in southern Victoria than from crops grown in the north of the State. Pollen is also collected from canola and bees foraging on this crop will need to be managed by the apiarist to avoid swarming.

Plant breeders use honeybee pollination in breeding programs for the development of new cultivars and hybrid canola seed. Honeybees are important cross-pollinators and can significantly improve the percentage set, yield and number of seeds per pod of male sterile lines. Small honeybee colonies are also used successfully for the pollination of canola plants isolated in insect-proof cages.

Apart from breeding programs, the benefits to be obtained from honeybee pollination in normal production crops will vary according to the particular cultivar and the conditions in which the crop is grown. Honeybee pollination may help to shorten the flowering and maturation periods of the crop thereby providing a more even ripening prior to harvest. Some trials have found that as the distance between plants and hives increased the percentage set, total seed yield and oil content decreased slightly.

Researchers have compared yields of plots caged to exclude bees and plots open to bees. In some cases, honeybee pollination has increased the number of ovules fertilised and number of pods set per plant crop, but most of these trials have demonstrated only small increases in total seed yield or none at all. More recently, research in Western Australia has demonstrated a potential to increase seed yields by up to 16 percent for the cultivar Karoo.

Growers should carefully determine if there are economic benefits to be gained by hiring honeybee colonies for this crop. Growers are also encouraged to seek information from agronomists about the pollination requirements of newly released cultivars.

Clover

Clover flower heads have many florets (individual flowers) which require pollination before seed can be set.  Each floret has to be ‘tripped’ before it can be successfully pollinated.  Tripping occurs when a bee inserts its tongue into the floret and depresses the keel petal.  Pollen is then deposited on the underside of the bee by the staminal column.  When the next floret is visited and tripped, the stigma of that flower makes contact with the pollen on the underside of the bee resulting in pollination.  The transfer of pollen from plant to plant by bees results in cross-pollination and a high seed set.

White clover

Cross-pollination from flower to flower is largely required in most clones for seed to be set.  Individual florets that have been pollinated wither quickly and effective pollination is indicated by a ring of withered florets at the base of a healthy, fresh-looking flower head.  An absence of withered florets on a flower head can indicate that pollination has not yet occurred and that there may an inadequate population of bees and other insects.  Ladino clover also requires a good population of bees.

 In Victoria, plots of cultivar Haifa caged to exclude insect visits and plots open to insects produced seed yields equivalent to 13 kg and 403 kg per hectare respectively.  Honeybees comprised 88% of all insects foraging on the crop.  The trial found that for maximum seed yields to be obtained, honeybee colonies should be placed in or adjacent to the crop for the entire flowering period.

Strawberry clover

Clones of this clover have varying degrees of self-fertility.  All clones will produce higher yields when cross-pollinated by honeybees, even those that produce seed by automatic self-pollination.

Alsike clover

This crop requires cross-pollination and a high population of bees is needed for an economic set.

Red clover

Cross-pollination is essential for red clover.  Honeybees visit the flowers for both nectar and pollen and when placed in cages bees have provided effective cross-pollination leading to good seed yields.  However, honeybees have difficulty in reaching the nectar at the base of the long corolla tube in individual florets of some cultivars.  The tripping process tends to be more violent in this species than in other clovers.  Where there is attractive flora nearby, many bees may choose not to visit the red clover.  As a result, very high colony stocking rates may be required to make up for the loss of bees that choose to visit other flowers.

 

Cucurbits

Introduction

The pollination requirements of cucumber, melons, pumpkin, squash, water melon and zucchini are very similar.

Almost all cucurbits require insect pollination. This is because the pollen grains are large and sticky and are unlikely to be carried by wind. Sometimes hand pollination may be used to pollinate small cucurbit crops grown in greenhouses, but this method is both time consuming and costly in terms of labour.

The presence of a number of developing fruits or fruitlets may inhibit further set because the bearing capacity of the cucurbit plant has been reached. Where fruits are picked on a continual basis (eg zucchinis), plants will continue to produce female flowers and set fruit.

Provided the crop is growing well, honeybee pollination can help to ensure a high yield with good high quality fruit that is well shaped.

Some introductory terms

Monoecious flowers

Generally, cucurbits have separate male (pistillate) and female (staminate) flowers that appear on the same plant or vine. Both male and female flowers produce nectar. Pollen is available from male flowers only.

Hermaphrodite flowers

Melons, such as cantaloupes, musk melons and water melons also have flowers that contain both female and male sexual components in the one flower. Automatic pollination is unlikely to occur and the pollen has to be transferred to the stigma by insect or by hand pollination.

Gynoecious cultivars

Plants belonging to these cultivars produce entirely or predominantly female (pistillate) flowers.

Duration that flowers are open

Cucurbit flowers are usually only open for one day and it is therefore important that sufficient bees are present in the crop to ensure best possible pollination results.

Pumpkins, marrow, squash and zucchinis

These crops bear separate male and female flowers; nectar is available from both pistillate and staminate flowers. Male flowers yield pollen which is collected by bees.

Repeated visits by bees are necessary to deliver a good number of pollen grains to the stigma and this helps to ensure:

• A good set
  
• A high number of ovules are fertilised with a corresponding number of seeds
  
• An increase in weight of fruit.

In Victoria, research has shown that the percentage set of pumpkins varied according to the ratio of bees to flowers. When bees were present in the ratio of one bee per 1.5 flowers, a 95% set was obtained. Ratios of one bee per 2 flowers and one bee per 2.6 flowers resulted in lower sets of 58% and 50% respectively.

Recommendations for honeybee colony stocking rates vary for this group of cucurbits. For example, one strong colony per hectare is suggested for pumpkins, although this rate could be increased to 2.5 colonies/ha for high value pumpkin crops. The term ‘high value’ is not explained, but it is presumed that the high stocking rates are used when crops have a large number of plants and large number of flowers to be pollinated per hectare.

The suggested stocking rate for marrows, squash and zucchinis is 2.5 strong colonies per hectare. Some recommendations suggest up to 4 colonies/ha.

Melons - canteloupes, rock melon, musk melon

Some species have separate male and female flowers, others have both male and hermaphrodite flowers. Nectar is produced in both male and hermaphrodite flowers.

Studies have shown that honeybee pollination can ensure greater melon production than when bees are not present in a flowering crop. Not only are there more melons, but individual melons are larger. Honeybees are also used effectively for the pollination of melons grown in glasshouses.

A trial conducted in the Murrumbidgee Irrigation Area of NSW (Williams, 1985) compared the yield of melons in plots caged to exclude bees and open to bees. The results indicated that honeybees increased:

• The total number of rock melons by 25%
  
• Average melon weight by 40%.

Results from overseas trials suggest that these findings may be somewhat conservative.

Pollination is an important factor that determines the quality and marketability of melons in terms of size and shape. High numbers of seeds in individual melons will go a long way to ensuring they meet market standards. Melons with less than 400 seeds are considered unmarketable because they are more likely to be under size and misshapen.

Recommended stocking rates vary, but are generally in the range of 2 to 2.5 strong colonies per hectare. Some reports indicate that on occasions bees collect little nectar from melons and colonies can lose weight and may need feeding with sugar.

Cucumber

Cucumbers have male and female flowers. However, hybrid gynoecious cultivars that produce almost entirely female flowers are grown in situations where a once-only harvesting by machine is used. These gynoecious cultivars need to be planted close to monoecious cultivars so that cross-pollination may take place.

Honeybee pollination can increase fruit set, number of seeds per fruit and number of fruit harvested. For example, Free (1993) quotes research findings indicating that 50 bee visits per flower resulted in larger cucumbers with more seeds than fruit originating from flowers visited by only 6-8 bees. Significant yield increases resulting from honeybee pollination have been found by other trials. Honeybees have been successfully used for the pollination of cucumbers in greenhouses.

The presence of several maturing cucumber fruits tends to have an inhibitory effect on further fruit set. This should not be taken as an indicator of poor pollination. The plant has simply reached its bearing capacity.

Several stocking rates for colonies have been suggested with higher rates being used for pickling cucumbers. Gynoecious hybrids require at least 7.5 per hectare. Up to 7.5 colonies have been suggested for an area of 0.4 hectare of pickling cucumbers with up to 370,000 plants. In other situations, 1, 2.5, or 5 hives per hectare are recommended.

Water melon

This melon also has male and female flowers on the same plant. Self-fertile, bisexual (hermaphrodite) flowers can also occur in some cultivars.

Several research reports indicate poor set when pollinating insects are absent. For example, eight visits per female flower by bees produced a better set than did four bee visits. Hermaphrodite flowers produced no fruit when insects were excluded from them, but in comparison, 95% of flowers open to insects set melons.

Bees gather nectar from male and female flowers. Recommendations for colony stocking rates vary from 0.5 to 7.5 colonies per hectare; 2 or 2.5 colonies could be considered to be the average stocking rate.

Seedless watermelons do not produce viable pollen and therefore require cross-pollination (Kelly 2000). To ensure adequate pollen is available, rows of a polliniser cultivar are interspersed between rows of the seedless watermelon. The optimum planting ratio is one polliniser row to every two rows of the seedless cultivar. The minimum ratio should not be lower than one polliniser row to every four rows of the seedless cultivar. Growers must also carefully time the planting of the seedless and polliniser cultivars so that both flower at the same time. Manning (1995) indicated that some triploid/seedless cultivars do not need pollination. Growers should confirm the pollination requirements of the cultivar they intend to grow before planting occurs.

Introduction of honeybee colonies to cucurbit crops

Colonies are best introduced just before the first female flowers begin to open. Male flowers will have been in bloom for some time before female flowers begin to appear.

Honeybee colony strength

Strong colonies with 6-8 frames of brood in two-storey hives are used. Honeybees will forage on all cucurbits, but they find cucumbers and zucchinis the least attractive. In some cases it may be necessary to control flowering weeds to minimise competition from other flowering plants.

 

Faba Beans

This legume plant has about 50-80 flowers which appear in clusters at the base of the leaves. Not all flowers produce pods and it is common for a relatively large number of flowers and young pods to be shed by the plant. Flowers usually contain 3 or 4 ovules, but sometimes up to 11 ovules may occur.

Faba bean crops contain hybrid plants capable of self-pollination and self-fertilisation, and plants that require cross-pollination. This means that the crop is capable of setting a certain amount of seed without insect pollination, but the addition of honeybee pollination will improve the yield. Seed resulting from cross-pollination produces more vigorous plants than does seed originating from self-pollinated flowers.

Experiments in southern New South Wales compared seed yields of plots open to bees and plots caged to exclude bees. The results showed that faba bean yields increased by 25% when a good population of honeybees was present in the crop. Yield increases of 35% as a result of honeybee pollination have also been demonstrated in overseas trials. In one trial, flowers pollinated by honeybees had 27% more pods/stem and 14% more seeds/pod than flowers that were self-pollinated. Bee activity can also cause early pollination and a shorter period of set which in turn leads to a more compact period of maturing and easier harvesting.

The scent of faba bean flowers is attractive to honeybees, but the bees are unable to collect the nectar because their tongues are not long enough reach it. Honeybees readily collect faba bean pollen although some colonies may be less enthusiastic than others in carrying out this task and may choose to visit other flowers.

Bee activity on this crop will vary according to the time of day. Individual flowers first open around mid-afternoon. On the following day they re-open about midday and then from mid-morning for the remaining days that they open in bloom. Observations for satisfactory bee activity and stocking rates in this crop should therefore only be conducted around mid-afternoon.

Honeybee crop pollination services

Honeybee colonies may be brought to the crop so that there are enough bees to perform the pollination task and achieve the best possible seed set. Leaving pollination to feral honeybee colonies can be risky because there are usually not enough bees and they may not be close enough to visit all sections of the crop.

 

Kiwifruit

This crop bears male and female flowers on separate vines. For fruit set to occur, pollen must be transferred from male flowers to female flowers.

Kiwifruit flowers do not yield nectar. Bees collect dry pollen from male flowers that is somewhat difficult to collect and sticky, but sterile pollen from female flowers. This all means that kiwifruit flowers are not all that attractive to bees when compared to other plants.

High numbers of bees are required for optimum pollination of this crop. Female flowers must be visited by bees more than once to achieve fertilisation of a high proportion of the many ovules within the ovary.

Fruit with high numbers of seeds will develop into good-sized and even-shaped quality fruit that conforms to current market standards. Fruit with low numbers of seeds will be small, lop-sided and generally unmarketable. Misshapen fruit and low numbers of seeds indicates a pollination problem.

Colonies should be placed in sheltered, well drained, sunny positions on the edge of blocks or on headlands within blocks to ensure the bees fly well. This is preferable to the placement of hives under kiwifruit canopies where the effect of shade, poor light and cold seriously reduce honeybee activity. Groups of hives are generally placed no more than 100-200 metres apart and no vine should be further than 200 metres from a hive.

Feeding sugar syrup to hives in kiwifruit orchards will help to stimulate honeybee brood rearing and collection of pollen. These two factors will help to ensure optimum honeybee foraging activity and therefore pollination. Sugar feeding will also help the bees to maintain adequate food reserves in their hives. Many kiwifruit growers now routinely feed syrup, usually every second day, to the colonies they hire.

 

Lucerne

Each individual lucerne flower has to be ‘tripped’ for pollination and seed set to occur. Tripping occurs when a bee inserts its tongue into the flower and depresses the keel petal. Pollen is then deposited on the underside of the bee by the staminal column. When the next flower is tripped by the bee, the stigma of the flower makes contact with the deposit of pollen and pollination results.

A high population of bees in this crop will create intense competition for nectar and pollen which in turn will result in a high rate of cross-pollination. Cross-pollination results in the development of larger seeds and more seeds per pod than that obtained by any self-pollination. A high population of bees will also ensure that flowers will be visited almost as soon as they open. This results in early pollination and the potential for pods to contain the maximum number of seeds.

Honeybees soon learn to avoid tripping the lucerne flowers. This is because tripping causes the staminal column to strike a bee with a certain amount of force and sometimes trap the bee for a brief moment. Nectar gatherers begin to visit the flowers from the side and this behaviour fails to trip the flower. Where flowers are tripped by ‘side workers’ self pollination occurs and a low set of seed will result. Pollen gatherers while modifying their foraging behaviour continue to trip the majority of flowers they visit.

Production of seed lucerne will not be successful unless honeybee colonies are brought to the crop so that there are enough bees to perform the pollination task. Leaving pollination of this crop to feral honeybees only will not provide the desired result.

 

Lupins

The blue lupin (Lupinus angustifolius) and the white lupin (L. albus) are grown predominantly as an important source of protein for various stock foods. Unfortunately, there have been few studies on the pollination of lupins and there appears to be little detailed information available.

These two lupins can set seed with their own pollen and automatic self-pollination occurs within the flower. However, research trials conducted in Russia have demonstrated improved seed yield, pod length and number of pods in some cultivars of both blue and white lupin when using honeybees.

Australian trials have shown similar results. In a trial using the white lupin cultivar Hamburg in north-east Victoria, yields of plots visited by honeybees and other insects were compared to yields obtained from plots caged to prevent insect pollination. Honeybee pollination significantly increased the yield of seed by 32% (95% of the insects visiting the crop were honeybees). Similar results were also obtained in a crop of blue lupin cultivar Uniwhite where the seed yield obtained from insect visited plots increased by 23% in comparison to caged plots.

Honeybees collect good quantities of pollen from both blue and white lupins. In the Victorian trials, most bees foraged for nectar and the colonies expanded their brood area and adult populations but the quantity of lupin honey stored in the hives was not large.

Honeybee crop pollination services

Honeybee colonies may be brought to the crop so that there are enough bees to perform the pollination task and achieve the best possible seed set. Leaving pollination to feral honeybee colonies can be risky because there are usually not enough bees and they may not be close enough to visit all sections of the crop.

 

Plums and Prunes

Japanese plums are generally self-infertile and require cross-pollination. Although a number of European plums are considered to be self-fertile, cross-pollination will help to ensure the setting of an adequate crop. Some exceptions do apply however and it is advisable to seek advice from a fruit tree nurseryman on the pollination requirement of specific cultivars.

Growers have two choices to obtain pollination

Ensure adequate numbers of bees are evenly distributed throughout the crop by using honeybee crop pollination services provided by beekeepers on a fee-for-service basis.

Leave pollination to feral honeybees. This is risky because there may not be enough feral bees in the immediate area. Their numbers may fluctuate from season to season as a result of disease, pesticides and drought. The location of their nests usually results in poor distribution of bees throughout the crop. Bees on a neighbouring property will most likely be too distant to provide you with optimum pollination.

This leaflet describes orchard management practices relating to honeybee pollination. The steps will enable growers to obtain the best results from pollination services by providing the bees with every opportunity to complete their task.

Benefits provided by honeybee crop pollination services

• Honeybees are proven pollinators and can influence fruit set of plums for higher yields
  
• Populous honeybee colonies can be moved into crops to ensure optimum numbers of bees
  
• Hives may be distributed throughout the crop to ensure bees visit all trees
  
• Feral honeybee numbers can be supplemented to ensure adequate numbers of bees

 

Pome Fruits

Honeybees can provide the pollination required for the production of apples, pears, nashi fruit and quinces that meet current quality standards and have good marketability.

Pollination is essential for fruit set and the formation of seeds. Seeds produce hormones that beneficially affect growth and size of individual fruit. Fruits with seeds distributed evenly in the ovary are uniformly shaped, but those with seeds unevenly distributed are usually misshapen.

 Growers have two choices to obtain pollination

• Ensure adequate numbers of bees are evenly distributed throughout the crop by using honeybee crop pollination services provided by beekeepers on a fee-for-service basis. Hives can be distributed in the crop to ensure that all trees are visited by bees.
  
• Leave pollination to feral honeybees. This is risky because there may not be enough feral bees. Their numbers may vary from season to season as a result of disease, pesticides and drought. The location of feral nests usually some distance from the crop will result in a poor distribution of bees throughout the orchard. This also applies to bees introduced to your neighbour's property.

Summary of benefits provided by honeybee pollination services

Honeybees are proven pollinators and can influence:

• Fruit set (eg. in a research trial, 240 fruit/100 flower clusters on apple trees open to bee visits compared to 8 fruit/100 clusters on apple trees caged to prevent bee visits)
  
• Seed numbers for improved fruit quality in terms of shape and size (7 seeds per fruit on open trees; compared to 2 seeds per fruit on caged trees) and improved storage life
  
• Early pollination before ovules begin to degenerate (research has shown that pollination of ‘Delicious’ flowers 48 and 72 hours after flower opening produced low sets of 11% and 3% respectively)
  
• Optimum pollination of king blooms for quality fruit.

 

Sweet Cherries

Honeybees are effective pollinators of cherries. Provided compatible pollen is available for pollination and fertilisation of ovules, trees visited by honeybees will have a greater set and yield of fruit than trees not visited by bees (35 kg compared to 2 kg respectively in a research trial in Victoria).

The need for cross-pollination

Cross-pollination is the transfer of pollen from one cultivar to another cultivar. Cross-pollination is necessary for the many cultivars of cherries that are self-incompatible. These cultivars cannot set crops unless pollen is received from another compatible cultivar. There are at least 13 incompatibility groups of sweet cherries and it is important that a suitable pollinser is chosen from the right group. Growers are advised to seek information about the pollination requirements of each cultivar to be grown from a fruit tree nursery. Nursery staff can also provide information on universal pollen donors and self-fertile cultivars.

Growers have two choices to obtain pollination

• Ensure adequate numbers of bees are evenly distributed throughout the crop by using honeybee crop pollination services provided by beekeepers on a fee-for-service basis.
  
• Leave pollination to feral honeybees. This is risky because there may not be enough feral bees. Their numbers may vary from season to season as a result of disease, pesticides and drought. The location of feral nests usually some distance from the crop will result in a poor distribution of bees throughout the orchard. This also applies to bees introduced to your neighbour's property.

Benefits provided by honeybee crop pollination services

• Honeybees are proven pollinators and can influence fruit set of cherries for higher yields.
• Populous honeybee colonies can be moved into crops to ensure optimum numbers of bees.
• Hives may be distributed throughout the crop to ensure bees visit all trees.
• Feral honeybee numbers can be supplemented to ensure adequate numbers of bees.

Inside this leaflet are a number of steps that will enable growers to achieve the best results from pollination services by providing the bees with every opportunity to complete their task.

Other

For all other applications, please enquire