POLLINATORS POLLINATION AND FOOD PRODUCTION

THE ASSESSMENT REPORT ON POLLINATORS, POLLINATION AND FOOD PRODUCTION
this bee species (e.g., Richards, 1984). Alfalfa (Medicago
sativa) is a Eurasian crop introduced to North America as an
important foodstuff for cattle, but honey bees are often poor
pollinators of alfalfa (Free, 1993). Following a presumably
earlier unintentional introduction of M. rotundata to the east
coast of North America around 1930 from Eurasia, where
it is native, the species had made its way to central and
western USA by the 1950s, where large areas of alfalfa
were grown for seed. Not only is M. rotundata an excellent
pollinator of alfalfa, it also nests gregariously in artificial
domiciles. Targeted research revealed important aspects
of its biology, and a viable industry in alfalfa leafcutter bee
management became established (Stephen 1961, 1962;
Bohart, 1962; see also Pitts-Singer and Cane, 2011).
Official figures on the size of the industry (number of bees
produced) are lacking, but an estimated 800 million alfalfa
leafcutter bees are traded commercially per year and a
further 1,600 million are encouraged in and around alfalfa
fields by bee-friendly farming practices and provision of
nesting medium in the USA (Peterson et al., 1992, Reisen
et al., 2009), with a sizable industry in Canada, too, that
also supplies M. rotundata from largely pathogen-free
areas in Canada to the US market. Land surrounding
alfalfa fields in the USA is also occasionally managed for
the ground-nesting alkali bee Nomia melanderi, which is
also an efficient alfalfa pollinator. Management involves not
only the enhancement of natural nesting sites but also the
actual building of completely artificial nesting sites, called
bee beds (Johansen and Mayer, 1976). The species has not,
though, been commercialised to any extent (Cane, 2008),
and neither has Rhophitoides canus, another groundnesting
solitary bee successfully managed for alfalfa seed
production in eastern Europe (Ptacek, 1989 in Bosch,
2005). Pollination of alfalfa makes a strong case for the
diversification of managed pollinators.
Leafcutter and mason bees are all solitary, and the diversity
of these and other species employed in (semi-)commercial
enterprises remains small. In Japan, the native Osmia
cornifrons has been successfully managed since the 1940s
for improved apple pollination (Yoshida and Maeta, 1988;
Maeta, 1990), where it is traded and used to pollinate 70%
of the apple production area (Maeta, 1990). In Europe, an
estimated one million Osmia bicornis (=rufa) bees are traded
per year for apple and other fruit pollination by 10-20 small
companies, while Osmia cornuta in central and southern
Europe and Osmia lignaria in the US and Canada are being
traded to the same or greater extent for the pollination of
orchard crops (Bosch and Kemp, 2002). In the tropics,
other largely solitary species such as carpenter bees (genus
Xylocopa) have been experimentally managed as potential
pollinators of crops such as passion fruit (Passiflora edulis,
Junqueira et al., 2012; Junqueira et al., 2013), whose flower
morphology does not allow efficient pollination by honey
bees. In Australia, the native blue-banded bee Amegilla
chlorocyanea is as efficient as bumble bees in pollinating
tomatoes grown in glasshouses (Hogendoorn et al., 2006).
This list in not exhaustive.
3.3.6 Other managed pollinators
The commercial management of other insect pollinators has
great potential (Kevan et al., 1990, Howlett, 2012), but is
currently on a much smaller scale than that of honey bees,
bumble bees or solitary bees. Flies were occasionally used
for strawberry pollination in the 20 th Century (Free, 1993).
However, this practice has been largely replaced by Bombus
pollinators, considered more efficient crop pollinators than
flies. Bumble bees need to gather large quantities of pollen
and nectar for their offspring and so are far more consistent
flower visitors than flies (Free, 1993). Blowflies and syrphid
flies can also be important pollinators of crops grown for
seed in cages (to control cross-pollination), e.g. the blowfly
Calliphora vomitori for the pollination of onion grown for
seed (Currah and Ockendon, 1983), and are also available
commercially. As mentioned above, another species of
fly, Lucilia sericata (common green bottle fly), is available
commercially for pollination (section 3.2.3).
3.4 TRENDS IN INTRODUCED
POLLINATORS AND
TRANSMITTED PATHOGENS
3.4.1 Outline of section
This section provides a general overview of trends in
pollinator introductions to novel habitats and its ecological
effects, especially those related with disease transmission.
It discusses the different concepts related to pathogen
transmission and the existing evidence for honey bees,
bumble bees, and leaf cutter bees. The frequency of
introduced species and the prevalence of different infectious
diseases on a worldwide scale is summarised according to
the existing evidence.
3.4.2 Ecological effects of
introduced pollinators
In this section, the term ‘introduced species’ will be used as
synonymous with ‘non-native species’ to denote a species
that lives outside its original distributional range, which
has arrived there by human activity, either deliberate or
accidental, and is able to survive and reproduce in the new
habitat without human assistance. An introduced species
might become an invasive species if it can outcompete
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3. THE STATUS AND TRENDS IN POLLINATORS
AND POLLINATION