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Bee pollination benefits for nut crops

Extract from Bulletin 4298: Honeybee pollination

The data in this report on the number of beehives required for each hectare of crop are estimates based on experience of researchers in Australia and overseas. The recommended numbers vary greatly and are due to differences between variety requirements, localities and the influence of local feral bee populations on pollination. Therefore, the reader will often be presented with more than one recommendation for a given number of hives per hectare.

Symbols used in the summaries

Note: Hazel nuts, walnuts and chestnuts are wind-pollinated.

Click on the name of a nut crop to go to information about it.

See also: 'Beetubes'.

Coconut (Cocos nucifera)

Flowering:

Almost year round.

Hives per hectare:

2 to 3.

Foraging:

Honey bees (Apis mellifera) tended to forage in the morning but their duration of foraging ranged from 8 am to 2 pm (in Brazil) whilst another common bee, Augochlora sp was active between the hours of 8 am and 11 am. Honey bees visited coconut palm flowers throughout the year. On tall varieties of coconut there were an average of 44 bees/inflorescence and on dwarf varieties 36.5 bees/inflorescence were observed in Brazil - Ref. 2.

Nectar production:

High. An important nectar source for bees in Brazil (Ref. 2).

Honey production:

Amber, good quality.

Review of bee pollination benefits

• The European honey bee (Apis mellifera) and the Asian honey bee (Apis cerana) are outstanding pollinators of coconut palms (Ref. 1).
• The predominant bee species pollinating Cocos nucifera cv Brazilian Tall and cv Brazilian Dwarf was Apis mellifera (European honey bee) whilst another species Augochlora sp accounted for 23% of visits. The relative abundance of Apis mellifera was greater on tall trees (66%) than on the dwarf varieties whereas Augochlora sp concentrated its visits on dwarf palms (93%). There was a highly significant difference in the distribution of these two species among tall and dwarf palms. - Ref 2.
• Wind-pollinated.
• Increased yields (up to double) when beehives are present in plantation (India).

Abstracts of scientific papers on coconut pollination

1. TITLE: Research station for coconut cropping systems
   ABSTRACT: Information on the role of honey bees as pollinators in coconut-based mixed cropping systems in Indonesia is provided. Honey bees are very important in the pollination of coconut. Without bees, the fruit setting of palms, tall or dwarf ones drops drastically. Outstanding pollinators are Apis mellifera (European honey bee) and Apis cerana indica (Asian honey bee).
   Apart from coconut and related palm species, the bees visit a wide range of crops including wild plants to collect nectar and pollen. This phenomenon provides an advantage in attracting the bees to coconut-based mixed cropping systems.
   The occidental species A. mellifera is well known as a high yielding species in producing honey and sometimes forages coconut palms besides Mimosa spp. or other crops. The oriental species A. cerana shows fidelity to coconut palm, but is less productive. It resembles A. mellifera in behaviour. The honey of these two species may provide additional income for small landholders.
   AUTHOR: Munaan, A.
   JOURNAL: Indonesian Agricultural Research and Development Journal 19(3): 43-49.
2. TITLE: Bees visiting coconut inflorescences in Bahia, North-east Brazil.
   AUTHOR: Castro, de M. S, Viana, B. F.
   JOURNAL: Journal of Apicultural Research 36(3/4): 180-181 (1997).

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Macadamia (Macadamia tetraphylla (light pink flowers): M. integrifolia (ivory white flowers) (Proteaceae))

Flowering:

2500 flowers per tree, although less than 0.3per cent produce nuts. Most flowers are partially self-sterile.

Hives per hectare:

5 to 8; 50 to 75 per 10 ha.

Nectar production:

Very little.

Review of bee pollination benefits:

• There was a highly significant difference (P = 0.001) between open and bee-excluded plots. Flowers that were exposed to bees in open plots were 87.5 per cent pollinated, and those flowers that were bee-excluded only had 9.1 per cent of the flowers pollinated (CSIRO).
• Nut yields increased in the presence of honeybee s.
• Majority of the insect visitors are nectar feeders.
• Honeybees and the native bee Trigona were the only insects to collect pollen (Trigona is probably the plant's native pollinator in Queensland).
• Insect activity of flowers was unrelated to temperature and humidity.
• Bees need to be primed to collect pollen by feeding sugar syrup.
• Fifty-five species of insect visited macadamia flowers in orchards in eastern Australia. Only Apis mellifera and Trigona carbonaria were common. The abundance of Trigona (but not Apis) was significantly and positively correlated with extent of surrounding eucalypt vegetation. Both species of bee showed no preference for heavily versus lightly flowering trees but preferred the outer racemes to shaded racemes. Trigona foraged for a mean of 7 hours per day whilst Apis foraged for 10 hours per day. Four bird species were also observed feeding on macadamia flowers (Qld).
• Honeybees pollinate macadamia flowers primarily whilst foraging for pollen.

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Peanut (Arachis hypogaea )

Flowering:

January to April. Largely self-fertile.

Review of bee pollination benefits:

• Feral honeybees increased crop by 7 to 11 per cent.
• Bee visits and subsequent pollination increased yields.
• Bee visits occur frequently and a high level of flower tripping occurs which assists and possibly increases self-pollination.

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Pecan (Carya illinoensis )

Review of bee pollination benefits:

• Wind-pollinated, especially in dry weather.
• Large amounts of green pollen produced that is highly attractive to bees.

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Pistachio (Pistacia vera )

Review of bee pollination benefits:

• Wind-pollinated.
• Honeybees collect pollen but do not visit female flowers.

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Cashew (Anacardium occidentale)

Flowering:

The hermaphrodite flowers have extremely strong floral scent. Flowers are self-fertile but not self-pollinating. One ovule exists in each ovary of each flower. Flowering peaks from 11 am to 12.30 pm. The stigma is receptive for one day.

The north of Western Australia flowering occurs from June to July. The period from pollination to harvest is about 40 days. Yields can range from 10 kg to 45 kg/tree.

Nectar production: Flowers are rich in nectar but nectar volume, concentration and total sugar can be significantly different between different cultivars. One day old flowers had significantly more nectar than two day old flowers. Genetic differences, initial volume of nectar at anthesis and patterns of evaporation and reabsorption of nectar determine the nectar available for collection (Ref. 2). These factors would affect the honey bees attractiveness to the crop and in the table below, honey bees would select cultivar 1 to forage which would result in better pollination.

Honey bee foraging:

In Brazil, honey bees visited 6.2 flowers/minute and spent 10.6 seconds foraging each flower (Ref. 1). Most pollen was deposited ventrally (under) the thorax of the honey bee in an area known as the mesothorax (underside middle near second leg) and metathorax (underside end near third leg). Some Brazilian native bees can be better pollinators of cashew than honey bees (Ref. 4).

Pollen:

Pollen germination was 93.7% when pollen was collected from flowers and after removing pollen from honey bees, germination dropped to 50% and six hours later it dropped further to 22.1% (Ref. 3). The average pollen count on honey bees was 1 241 (Ref. 5).

Review of bee pollination benefits

• Wind-pollinated
• A concentration of beehives would help pollination.
• Honeybees were effective cashew pollinators (Ref. 5)
• Flies and ants are the primary pollinators of cashew, but wasps and bees also forage the flowers.
• Cashew production can be increased by introducing honeybee colonies.

Abstracts of scientific papers on cashew pollination

• Foraging behaviour and pollination efficiency of the bee species Apis mellifera and Centris (Hemisiella) tarsata visiting cashew flowers
• Bee plants: volume, concentration and total sugar of nectar secreted by flowers of distinct genetic material of cashew
• Changes with time in the germinability of cashew pollen grains found on different body areas of its pollinator bees
• The pollination efficiency of foraging bees on apple and cashew
• Number and distribution of cashew pollen grains on the bodies of its pollinators, Apis mellifera and Centris tarsata

1. TITLE: Foraging behaviour and pollination efficiency of the bee species Apis mellifera and Centris (Hemisiella) tarsata visiting cashew flowers.
   ABSTRACT: Studies were carried out on the foraging behaviour and pollination efficiency of the 2 bee species visiting flowers of wild cashew trees growing in coastal areas of Beberibe, state of Ceará, Brazil. Individuals of the 2 species were observed in their visits to flowers, and the average number of bees visiting each cashew tree at 10 am over several days, the average number of flowers visited by each bee species within a minute and the average time spent per flower visit for each bee species were compared. The efficiency of each bee species in setting fruit after single visits to flowers was also studied. C. tarsata individuals were almost twice as abundant as A. mellifera foragers at 10 am and visited almost twice as many flowers per minute (4.22± 0.24 versus 2.18± 0.19 and 11.94± 0.12 versus 6.20± 0.17 respectively). Furthermore, visits to flowers by C. tarsata were half as long as visits made by A. mellifera (5.07± 0.04 seconds versus 10.59± 0.34 seconds. There was no significant difference between the number of flowers pollinated by single visits of each bee species, but C. tarsata pollinated more flowers per time unit. It is concluded that C. tarsata shows potential to be used for cashew pollination.
   AUTHOR: B.M. Freitas
   JOURNAL: Anais da XXXIII Reuniáo Anual da Sociedade Brasileira de Zootecnia, Fortaleza, 21 a 26 de julho, 1996 a. Volume 2 - Forragicultura, Sociedade Brasileira de Zootecnia 666-668 (1996).
   

2. TITLE: Bee plants: volume, concentration and total sugar of nectar secreted by flowers of distinct genetic material of cashew (Anacardium occidentale L.).
   ABSTRACT: Samples of nectar were collected from 1- and 2-day-old A. occidentale flowers, bagged and unbagged, at anthesis and when bees (Apis mellifera) were most frequent on the flowers. For nectar collected soon after anthesis, there were significant differences in volume, concentration and total sugar of nectar from the genetic materials CC2 (1.10± 0.02 µL; 19.85± 0.35%; 0.232± 0.003 mg), CCP 09 (0.94± 0.03 µL; 14.01± 0.33%; 0.134± 0.002 mg) and CC1 (0.31± 0.18 µL; 19.70± 0.55%; 0.060± 0.002 mg) respectively.
   At other times of the day nectar volume did not allow refractometer readings and only the volume was assessed. A 3-way analysis of variance showed differences among cashew types, and that the amount of nectar sampled from 1-day-old flowers and bagged flowers was significantly greater than the volume sampled from 2-day-old flowers and unbagged flowers. It is concluded that there is a significant variability in volume, concentration and sugar content of nectar secreted by flowers of cashew trees of distinct genetic constitution and that these parameters, the initial nectar volume of anthesis and patterns of evaporation and/or reabsorption of nectar, determine the nectar volume available for collection.
   AUTHOR: B.M. Freitas
   JOURNAL: Anais da XXXIII Reuniáo Anual da Sociedade Brasileira de Zootecnia, Fortaleza, 21 a 26 de julho, 1996 b. Volume 2 - Forragicultura, Sociedade Brasileira de Zootecnia 395-397 (1996).
3. TITLE: Changes with time in the germinability of cashew (Anacardiu occidentale) pollen grains found on different body areas of its pollinator bees.
   ABSTRACT: The in vitro germinability of A. occidentale pollen collected directly from flowers and from areas of Apis mellifera and Centris (Hemisiella) tarsata bodies, and its variations with time, were studied. Pollen collected from flowers showed 93.7± 2.3% germinability, while that collected from the frons, ventral mesothorax and ventral metathorax of A. mellifera and C. tarsata showed 21.0± 1.6%, 51.5± 4.4%, 50.2± 4.7% and 22.3± 1.7%, 51.5± 4.2% and 51.0± 4.3% germinability respectively. The average germinability of cashew pollen on the bodies of A. mellifera and C. tarsata at the time of capture of specimens was 50.0± 6.5% and 50.3± 6.3% respectively, and 6 hours later it was as low as 22.1± 2.7% and 22.4± 2.5% respectively. It is concluded that the level of germinability of pollen on a pollinator's body depends on pollen age and the body area in which it is found. This should be considered in the study of pollination efficiency of floral visitors.
   AUTHOR: B.M. Freitas
   JOURNAL: Revista Brasileira de Biologia 57(2): 289-294 (1997).
4. TITLE: The pollination efficiency of foraging bees on apple (Malus domestic Borkh) and cashew (Anacardium occidental L.).
   ABSTRACT: The increasing use of insects as pollinators in recent years has highlighted the need for a pollination efficiency index to estimate pollinator effectiveness. The aims of this study were to identify factors that could contribute to the pollination efficiency of floral visitors and to develop a general pollination index where the fitness of both male and female functions of a flower could be evaluated and the pollination efficiency of floral visitions could be determined. Pollen- and nectar-collecting honey bees (Apis mellifera) foraging on apples (Malus domestica) [= M. pumila] and honey bees and the solitary bee Centris (Hemisiella) tarsata foraging on cashew (Anacardium occidentale), were investigated between 1992 and 1994 in the UK and Brazil, respectively. A series of experiments covered the efficiency of these bees in acquiring fresh, viable pollen on their bodies; in accumulating and distributing pollen grains over their bodies; in transferring compatible pollen to stigmas; and in setting seeds and fruits. To help interpretation of the data, the floral biology of apple and cashew were extensively investigated. Interpretations of the plant species' pollination strategies and how interactions with the foraging strategy of the bees affect the pollinator's efficiency, are given and discussed. A direct and comprehensive measure of pollinator effectiveness (GPEi), resulting from the arithmetic mean of the efficiency indices developed in this study for pollen removal from flowers, pollen acquirement by the pollinator's body, pollen transfer to stigmas and Spears' (1983) pollination efficiency index, is proposed. According to their GPEi, pollen-collecting honey bees are better pollinators of apples than nectar-collecting honey bees and C. tarsata is a better pollinator of cashew than honey bees. The usefulness and limitations of GPEi are discussed.
   AUTHOR: B.M. Freitas
   JOURNAL: PhD Thesis, University of Wales College of Cardiff, UK (1995).
5. TITLE: Number and distribution of cashew (Anacardium occidentale) pollen grains on the bodies of its pollinators, Apis mellifera and Centris tarsata.
   ABSTRACT: The number and distribution of Anacardium occidentale pollen grains on the bodies of Apis mellifera and Centris tarsata were studied at a site in NE Brazil. There was a significant difference between the number of pollen grains found on the bodies of male (av. 1805 pollen grains) and female (av. 2271 pollen grains) C. tarsata and foraging honey bees (N=1241). Microscopical studies of nine parts of the bees' bodies showed that cashew pollen was unevenly distributed and that it tended to remain on the body parts upon which it was initially deposited. Areas of the body which had greater densities of cashew pollen had also touched the cashew stigmas, supporting suggestions that Apis mellifera and Centris tarsata are effective cashew pollinators.
   AUTHOR: Freitas, B. M.
   JOURNAL: Journal of Apicultural Research 36(1): 15-22 (1997).

Page reviewed: March 2006