Bee Pollination of Crops

Plants have sexes somewhat same as animal do. Many plants carry both the male and female elements on the same flower while other has sex organs on the separate Plants. These plants require to be carrying from one plant to another plant of some species or other species to effect pollination. The transfer of male reproductive element (pollen) on the stigmas of flower is termed as pollination. The transfer of pollen from another to stigmas of the same flower of same plant is termed as self, while those involving the transfer of pollen from an anther to the stigma of a flower of flower of another individual plant is termed as cross pollination. Reproducing of off springs without involving the union of sperm and egg cells such as in rhizomes, tubers, grafts etc. is asexual reproduction. But most flowering plants reproduce sexually. For sexual reproduction the transfer of pollen from the male part (anther) to the stigma of the female part is required. This transfer of pollen from anther to stigma can take place within a flower or flowers of same plant or between the plants of similar genetic make up (self-pollination). But in cross pollination the transfer of pollen from the anther of one to the stigma of another plant with different genetic make up takes place. Cross pollination is to the benefit of the population and plants have various mechanisms to favour it and avoid self pollination. Cross pollination is brought about by external pollen transferring agents. A number of agents are necessary to effect pollination. These includes a biotic (wind, water, gravity etc.) and biotic (insects, bats, birds, snails and slugs etc.). Wind is the most important pollinating agent and many important crops like millets, maize, barley, wheat and rice are wind pollinated. Many types of animals also act as cross pollinators but amongst these, insects are important. Many wild bees are specialized for gathering nectar and pollen but some other insects such as flies, beetles and trips do visit the flowers to satisfy their own needs. These accidental visitors are poor or of no value pollinators except some species of flies. Of all the insects, true honeybees are by far the most important pollinators because their adults and young ones exclusively depend on ne4ctar and pollen, their body characteristics and foraging behaviour make them efficient pollinators and above all their population can be manipulated. But among all of them, the insects are the most important with bees (Apis spp.) accomplish more than 80 percent of the pollination by insects. Honey and bees wax or other hive products are the direct visible benefits from a bee colony but the bees do manifold useful service and greater benefits are accrued by their contribution in increasing crop yields. The beekeepers do a great service to the community or village than for himself. The value of bees of pollinator is first discovered by Koelreuter (1761), while knight first noted the relation between plants and hybrid vigor. Darwin's concept of natural selection opened the way for a fuller understanding of the correlation ship of bees and flowering plants, with resultant appreciation of factors affecting mutual adoption, speciation and distribution. Honey bees (Apis spp.) are the most important pollinators of agricultural and horticultural crops. Honeybees have attributes that makes them valuable for crop pollination. These can be marshaled in adequate numbers at desired places. Their body parts are modified to effect pollination. Their body size and proboscis length suits them to forage many varied types of flowers. Their wide host range enables them to pollinate much type of crops. They work for longer durations and are also less effected by adverse climatic conditions as compared to other insect pollinators. Their foraging behaviour patterns are highly favourable to qualify them as most efficient pollinators of crops. In addition to pollination services, colonies can be managed to produce honey, bee was, porpoise, royal jelly etc. which are all saleable products Out of four Apis species available in India, only Apis cerana Fabr. And the exotic Apis mellifera L can be managed esaliy for crop pollination the two wild species, Apis florae L and Apis dorsata Faber. Can not be domesticated and are therefore are not easily manageable in pollination, however they are very important pollinators of may crops. Techniques now have been developed for the transport and placement of these bees at desired locations at desired time. The forage preference, pollinating efficiency and density of bee species vary depending on the crop. The number of foragers bee at on a particular crop at my moment of time is determined by the colony size, weather factors (temperature, wind velocity, relative humidity, solar radiation etc.) and floral attractiveness (colour, odour) and nectar and pollen concentration of flower. Pollination requirements of crops have been attempted to be worked out in many crops. Use of honeybees for pollination is dependent on the natural pollinators already present in a locality but such pollinators are on the decrease due to advanced agricultural technologies and thus increased reliance on honeybees for pollination. Assessment of increase in yields due to bee pollination is difficult in some crops where the varieties are self-unfruitful. In such cases increases are unbelievable. Planned bee pollination is an input in crop husbandry in many parts of the world but in India this is receiving attention since any amount of effort in irrigation, fertilizers, plant protection etc. cannot compensate the good done by bee pollination. Following crops are benefited by bee pollination and yield can be increased by manifolds.

Table.2. Effect of bee pollination on yield increase of crops Insect pollination is a requirement for the production of many crops, but in agro ecosystem native pollinators are often too scarce to ensure adequate pollination. Large scale monoculture, necessary for economic production of mechanically cultivated and harvested crops provides of mechanically cultivated and harvested crops provides no continual source of pollen and nectar necessary to maintain strong colonies. The indiscriminate and widespread uses of pesticides highly toxic to bees either weakens to destroy many colonies or their use causes the beekeepers to relocate the colonies in profitable area. Intensive agriculture has reduced honeybee population to a point where they are insufficient for pollination of commercial planting.

Management of honeybee for Pollination:

1. Increasing the number of foragers

2. Attractants and sprayers

The purpose is to direct bees to crops. The bees perform recruitment dances and increase the numbers of bees visiting target crops, these includes:

a) Scented sucrose solution®
b) Food supplement sprays (eg. Beeline )
c) Pollen attractant
d) Pheromones and other chemicals.

3. Repellents

Repellents sprayed on the target crops reduce the bee forage and induce them to forage on the less attractive target crops e.g. carbolic acid, acetic acid, propionic anhydride, benzaldehyde, calcium chloride.
The mandibular glands pheromones, alarm pheromones can also be used.

4. Selection of breeding of honeybees

5. Management of honeybee colonies (moving colonies)

a) Timing: The colonies should be moved to a target crop blooms 5-10 percent, influence the number of foragers that are turn around it.
b) Distance from the crop: Placing the hive with in 0.5 km radius increases the crop pollination. Requirement of nest mates to the nearby sites is also greater as this information is more easily communicated. Colonies placed near crops collect more pollen and nectar, spend less time collecting load of pollen and nectar, the number of flights increases for both types with proximity to the floral source.
c) Number and placement: 3-5 colonies/hectare placed equidistant form each other within the crop is recommended. This number of colonies can be handled easily.
d) Replacement or Rotation: Colonies should be replaced or rotated with fresh ones when they begins to forage outside target crop. Colonies involved in these findings should be at least 2.4 kms apart or the bees may return to their former sites. This system is particularly useful, where the target crop e.g pear is relatively unattractive to bees.
e) Temporary placement: The flowers of crop generally present Their pollen/nectar at a certain times of the day. Thus confining the bees to their hive until to maintain bees, at least temporarily, on a crop.





6. Removing floral competition

Weeds or other non target crops should be eliminated or mowed when in flower, to avoid competition for foraging bees.

7. Pollen Dispensers

Pollen dispensers (pollen inserts) apply pollen to bees leaving Hives so that they can cross pollinate when few pollinizers varieties are available. This may increase pollination efficiency of bees without necessarily maintaining more of them in a target crop. Dispensers may stimulates foraging activity and that may induce bees to forage for the type of pollen in the dispenser.

8. Disponsable Pollination Units (DPU's)

DPU's are small comb less colonies housed in inexpensive containers that are trucked or parachuted into target crops that are inaccessible, and then destroyed or left to die when flowering is over. Conclusion Considering the importance of bees on crop pollination, more coordinated research is needed. In India the total cultivated areas is 189 million hectares and at least 1/3 area is under entomophilous crops which require pollination. At a very modest rate of 3 colonies/ hectare, 567 colonies of honeybees are needed as against the merely the one million colonies at present. It is very necessary to survey and delineate different agro-climatic zones to determines the distribution can be supplement of pollinating agents so that regions must also carry out observations on the pollen gathering activities of bees. The lean pollen gathering period can be corrected by planting suitable pollen and nectar yielding flora of that period. Pesticides applications wherever possible can be modified as soil application instead of spray, can avoid drift to nearby hives. The selection and breeding of honeybees for physical characters suited crops, form reduced flight, or for preference for specific pollens or nectar appear promising. Honeybees are the “angles or agriculture”, the farmers best friend. Using honeybees for crop pollination, the production can be increased manifolds, however it needs to be encouraged among farmers. Pollination by bees has thus become a essential factors in producing many crops along with the factors that are taken for granted.