Bees as pollinators in Brazil - USP

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Coffee, a special commodity
Most of the world coffee production is originated
from C. arabica shrubs, which are native
to southwestern Ethiopia, as well as from C.
canephora var. robusta (also known as C.
robusta), native to equatorial Africa. Coffea
arabica plants are typically grown in cold but
frost-free areas at elevations of 500-200m, and
C. canephora typically from sea level to 1000m
(Klein, et al., 2003a, Donald, 2004). Coffea
canephora is a self-sterile, diploid species, and
C. arabica is a self-sterile tetrapoid species
(Klein, et al., 2003a).
Traditionally, coffee farming involves the
planting of coffee bush under a selectively
thinned canopy of existing rainforest trees. This
combination of shading trees and coffee
shrubs form an integrated agroforestry system
(Donald, 2004). There are many benefits originated
from this way of production; first, shade
cover up to 50% increases yields, and the presence
of shade trees can control pest problems;
furthermore, the quality and size of coffee
beans, as well as the taste of the final product
are better under shade systems than under systems
without trees. However, this method was
replaced for a full-sun production in many
places. Where good soils and favorable climates
are present, this method produces higher
yields per unit area, although not necessarily
per plant. Nevertheless, this method also produces
some collateral effects, as an increased
rate of pest problems and secondary pesticide
problems. Nowadays, shading is only used
where it is necessary to reduce yields to keep
production sustainable in poor-nutrient soils,
where shade-loving varieties are grown, and
where shade trees form part of economic agroforestry
systems (Donald, 2004).
Another important issue related with coffee
production is the presence or absence of
pollinating insects. Formerly, the importance
of pollinators for coffee shrubs was neglect-
ed (Free, 1993), but in recent years their
importance is being evidenced after a series
of experiments made in several countries.
Here we describe these results in order to
show the importance of pollinators for the
coffee harvest.
A pioneer work in this area was performed
by Nogueira-Neto, et al., (1959), which
investigated the effect of the exclusion of pollinating
insects on the yield of the variety
Bourbon (C. arabica var. Bourbon) in a farm in
São Paulo State, Brazil. They found a tendency
(although the differences were not significant)
towards a higher production of fruits on the
plants that were allowed to receive the visit of
pollinating insects, in contrast to a control
group, which plants were not allowed to be
visited. They also observed several species of
native and introduced bees visiting coffee
flowers, as the introduced Apis mellifera and
the stingless bee Melipona quadrifasciata,
both relatively big sized bees, the most effective
pollinators of coffee flowers in their observations
(a total period of observations of six
years). According to the authors, the smaller
bees (Nannotrigona testaceicornis, Plebeia sp.,
Tetragonisca angustula, Trigona hyalinata and
T. spinipes) observed in the flowers, collecting
pollen and/or nectar were not so effective pollinators
as these big sized bees. They concluded
that for this variety of coffee (Bourbon),
insect visits are not so important as for the
diploid self-sterile species of Coffea arabica,
which needs the visiting of insects, especially
bees, as well as the wind, for their pollination
(Nogueira-Neto, et al., 1959).
Roubik (2002) strongly suggested the
importance of honey bees and native bees for
the increasing of pollination of C. arabica
plants in the New World, as well as in the Old
World. He found a positive correlation
between the coffee yields and the presence of
honey bees in the New World. As Africanized