POLLINATORS POLLINATION AND FOOD PRODUCTION

THE ASSESSMENT REPORT ON POLLINATORS, POLLINATION AND FOOD PRODUCTION
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6. RESPONSES TO RISKS AND OPPORTUNITIES ASSOCIATED
WITH POLLINATORS AND POLLINATION
become integrated into beeswax, heightening potential for
contamination of hive products (Rosenkranz et al., 2010).
Biocontrol of Varroa and other parasitic mites is a control
strategy with some preliminary investigations, including
laboratory demonstrations of lethality to Varroa of several
different bacterial strains (Shaw et al., 2002), but other
attempts have shown less impressive results, and no
commercial products or field beekeeping trials have used
this strategy (reviewed in Rosenkranz et al., 2010, Meikle
et al., 2012). Biocontrol of parasitic mites (and other
parasites and pathogens) thus represents an important
knowledge gap.
Parasitic mites, especially Varroa, are also controlled by
beekeeping practices and other cultural controls. One such
practice that has shown efficacy is the use of “trap frames”.
Gravid Varroa females prefer to lay their eggs in drone
(male) brood cells relative to worker (female) brood cells.
After the drone cells are capped, the drone brood can be
removed, thus greatly reducing Varroa populations within a
colony (Sammataro et al., 2000; Rosenkranz et al., 2010).
Similarly, swarming management can provide some level of
Varroa control given that departing swarms leave infected
brood behind (Sammataro et al., 2000; Rosenkranz et al.,
2010). Another method involves heating colonies to 44ºC,
a temperature that bee brood can survive but which kills
developing mites (Sammataro et al., 2000; Rosenkranz et
al., 2010). A cultural practice used in the control of Acarapis
tracheal mites is the addition of patties of vegetable
shortening and sugar to colony boxes, which may disrupt
the “questing” behavior of female mites searching for new
hosts (Sammataro et al., 2000). These cultural practices
are often labour intensive and difficult to implement in large
apiary operations (Rosenkranz et al., 2010). In solitary bees,
thermal shock treatments applied during the most resistant
bee stage (dormant prepupa) are used in Japan to reduce
numbers of Chaetodactylus mites in Osmia cornifrons
populations (Yamada, 1990).
6.4.4.1.1.2.4 Support social immunity mechanisms
in eusocial taxa
These are mechanisms by which social organisms help to
prevent and treat pathogens and parasite infestations at a
social (not individual) level (Cremer et al., 2007; Sadd and
Schmid-Hempel, 2008; Evans and Spivak, 2010; Parker
et al., 2011). This is a recently emerging area of study
with limited, but growing evidence that it can have a large
impact on disease pressure. Management to support social
immunity could include provision of resin-producing plants
so that honey bees can gather propolis and not removing
propolis from colonies (Simone et al., 2009; Simone-
Finstrom and Spivak, 2012), and dietary management to
support honey hydrogen peroxide production (Alaux, 2010).
A possible trade-off is that some practices interfere with
typical beekeeping practices (e.g., removal of propolis).
More field-scale trials of supporting social immune
mechanisms would assist pollinator managers and policy
makers in evaluating their implementation.
6.4.4.1.1.2.5 Manage pathogen and parasite
evolution
This category includes two broad responses. First,
development of resistance to insecticides and antibiotics is
a well-known phenomenon in agriculture (Brattsten et al.,
1986; Perry et al., 2011) and medicine (e.g., Neu, 1992),
respectively, which has also been documented in honey
bees in terms of resistance of Varroa mites to acaricides
(Milani, 1999). There is a body of evolutionary theory on
managing insecticide and antibiotic resistance, and lessons
from this work could be applied to treatment of disease
and parasites in managed pollinators. For example, the
length of treatment, treatment rotations, and treatment
combinations could be applied in ways to reduce resistance
(e.g., Comins, 1977; Lenormand and Raymond, 1998).
Second, there is a well-described relationship in evolutionary
theory between transmission of pathogens and virulence
(harm to the host), such that increased transmission tends
to select for increased virulence (e.g., Ewald, 2004). While
there is no direct evidence of such a relationship in managed
pollinators, this pattern has been detected in a broad range
of other host-pathogen systems (reviewed in Alizon et al.,
2009). Steps could be made to assess this relationship in
managed pollinators and potentially to alter management to
select for less-virulent parasites and pathogens by reducing
parasite transmission rates.
6.4.4.1.1.3 Genetic management
Genetic management, similar to general management, is
focused on multiple goals. There are four main methods of
genetic management: 1) traditional trait-focused breeding;
2) maintenance or enhancement of genetic diversity;
3) genetic engineering, i.e. development of transgenic
pollinators; and 4) high-tech breeding. The first of these is
traditional breeding for desirable traits, and in A. mellifera
there have been extensive breeding efforts, in particular
(though not exclusively) focused on hygienic behavior to
reduce disease and parasites (Spivak and Reuter, 1998,
2001; Ibrahim et al., 2007; Büchler et al., 2010). These
objectives have been successful in terms of target trait
modification, but there is limited knowledge of how bees
originating from such breeding programs perform relative
to other lines, in managed apiary contexts, in terms of
outcomes such as colony survival and productivity. While
there is at least one report of bees from “hygienic” breeding
programs outperforming typical (non-hygienic) stocks in
terms of both disease resistance and honey production
(Spivak and Reuter, 1998), other studies have not seen
consistent advantages of bees bred for Varroa resistance