The extent of our reliance on animal pollination for world crop production for human food has not previously been evaluated and the previous estimates for countries or continents have seldom used primary data. In this review, we expand the previous estimates using novel primary data from 200 countries and found that fruit, vegetable or seed production from 87 of the leading global food crops is dependent upon animal pollination, while 28 crops do not rely upon animal pollination. However, global production volumes give a contrasting perspective, since 60% of global production comes from crops that do not depend on animal pollination, 35% from crops that depend on pollinators, and 5% are unevaluated. Using all crops traded on the world market and setting aside crops that are solely passively self-pollinated, wind-pollinated or parthenocarpic, we then evaluated the level of dependence on animal-mediated pollination for crops that are directly consumed by humans. We found that pollinators are essential for 13 crops, production is highly pollinator dependent for 30, moderately for 27, slightly for 21, unimportant for 7, and is of unknown significance for the remaining 9. We further evaluated whether local and landscape-wide management for natural pollination services could help to sustain crop diversity and production. Case studies for nine crops on four continents revealed that agricultural intensification jeopardizes wild bee communities and their stabilizing effect on pollination services at the landscape scale.

/pdf/importance-of-pollinators-in-changing-landscapes-for-world-2j8o9ygr29.pdf

Importance of pollinators in changing landscapes for world crops

Pollinators are a key component of global biodiversity, providing vital ecosystem services to crops and wild plants. There is clear evidence of recent declines in both wild and domesticated pollinators, and parallel declines in the plants that rely upon them. Here we describe the nature and extent of reported declines, and review the potential drivers of pollinator loss, including habitat loss and fragmentation, agrochemicals, pathogens, alien species, climate change and the interactions between them. Pollinator declines can result in loss of pollination services which have important negative ecological and economic impacts that could significantly affect the maintenance of wild plant diversity, wider ecosystem stability, crop production, food security and human welfare.

/pdf/global-pollinator-declines-trends-impacts-and-drivers-5gfi4zur4k.pdf

Global pollinator declines: trends, impacts and drivers.

Bees are subject to numerous pressures in the modern world. The abundance and diversity of flowers has declined, bees are chronically exposed to cocktails of agrochemicals, and they are simultaneously exposed to novel parasites accidentally spread by humans. Climate change is likely to exacerbate these problems in the future. Stressors do not act in isolation; for example pesticide exposure can impair both detoxification mechanisms and immune responses, rendering bees more susceptible to parasites. It seems certain that chronic exposure to multiple, interacting stressors is driving honey bee colony losses and declines of wild pollinators, but such interactions are not addressed by current regulatory procedures and studying these interactions experimentally poses a major challenge. In the meantime, taking steps to reduce stress on bees would seem prudent; incorporating flower-rich habitat into farmland, reducing pesticide use through adopting more sustainable farming methods, and enforcing effective quarantine measures on bee movements are all practical measures that should be adopted. Effective monitoring of wild pollinator populations is urgently needed to inform management strategies into the future.

https://science.sciencemag.org/content/sci/early/2015/02/25/science.1255957.full.pdf

Bee declines driven by combined stress from parasites, pesticides, and lack of flowers

https://www1.montpellier.inra.fr/lameta/articles/5.4.2_POLLINATION.pdf

Economic valuation of the vulnerability of world agriculture confronted with pollinator decline

Plant essential oils for pest and disease management

Various levels of wax deprivation in honey bee (Apis mellifera) colonies induced shifts in the temporal pattern of division of labour in worker honey bees. The most extreme wax stress induced an earlier onset of foraging, and an increase in comb building and the production of wax scales. Moderate wax stress induced only an increase in comb building and production of wax scales. No significant differences in development of hypopharyngeal gland acinal diameter were found, suggesting that production of wax and brood food and associated behaviour patterns develop and decline independently. The graded changes in behavioural response to various levels of stress found in this study support the concept of a reserve labour force in honey bee colonies, which can respond to stress through shifts in caste ontogeny.

The influence of wax deprivation on temporal polyethism in honey bee (Apis mellifera L.) colonies

Queen rearing is suppressed in honey bees (Apis mellifera L) by pheromones, particularly the queen's mandibular gland pheromone In this study we compared this pheromonally-based inhibition between temperate and tropically-evolved honey bees Colonies of European and Africanized bees were exposed to synthetic queen mandibular gland pheromone (QMP) for ten days following removal of resident queens, and their queen rearing responses were examined Queen rearing was suppressed similarly in both European and Africanized honey bees with the addition of synthetic QMP, indicating that QMP acts on workers of both races in a comparable fashion QMP completely suppressed queen cell production for two days, but by day six, cells containing queen larvae were present in all treated colonies, indicating that other signals play a role in the suppression of queen rearing In queenless control colonies not treated with QMP, Africanized bees reared 30% fewer queens than Europeans, possibly due to racial differences in response to feedback from developing queens and/or their cells Queen development rate was faster in Africanized colonies, or they selected older larvae to initiate cells, as only 1 % of queen cells were unsealed after 10 days compared with 12% unsealed cells in European colonies

Suppression of queen rearing in European and africanized honey bees Apis mellifera L. by synthetic queen mandibular gland pheromone

Studies of Varroa destructor orientation to honey bees were undertaken to isolate discrete chemical compounds that elicit host-finding activity. Petri dish bioassays were used to study cues that evoked invasion behaviour into simulated brood cells and a Y-tube olfactometer was used to evaluate varroa orientation to olfactory volatiles. In Petri dish bioassays, mites were highly attracted to live L5 worker larvae and to live and freshly freeze-killed nurse bees. Olfactometer bioassays indicated olfactory orientation to the same type of hosts, however mites were not attracted to the odour produced by live pollen foragers. The odour of forager hexane extracts also interfered with the ability of mites to localize and infest a restrained nurse bee host. Varroa mites oriented to the odour produced by newly emerged bees (<16 h old) when choosing against a clean airstream, however in choices between the odours of newly emerged workers and nurses, mites readily oriented to nurses when newly emerged workers were <3 h old. The odour produced by newly emerged workers 18–20 h of age was equally as attractive to mites as that of nurse bees, suggesting a changing profile of volatiles is produced as newly emerged workers age. Through fractionation and isolation of active components of nurse bee-derived solvent washes, two honey bee Nasonov pheromone components, geraniol and nerolic acid, were shown to confuse mite orientation. We suggest that V. destructor may detect relative concentrations of these compounds in order to discriminate between adult bee hosts, and preferentially parasitize nurse bees over older workers in honey bee colonies. The volatile profile of newly emerged worker bees also may serve as an initial stimulus for mites to disperse before being guided by allomonal cues produced by older workers to locate nurses. Fatty acid esters, previously identified as putative kairomones for varroa, proved to be inactive in both types of bioassays.

Semiochemicals influencing the host-finding behaviour of Varroa destructor.

Variation in polysubstrate monooxygenase activity, as measured by the epoxidation of aldrin, was studied in colonies of the honey bee, Apis mellifera L. Significant differences were found among colonies in spring, summer, and fall. In addition, colonies varied in their detoxification capacity from season to season, being least able to metabolize aldrin in the spring. Significant regression of the LD50 of diazinon on aldrin epoxidase activity indicated the involvement of these enzymes in determining intercolony diazinon resistance. The results also suggest that studying a number of populations with quantitatively different monooxygenase activities can give information on the in vivo metabolism of phosphorothioate insecticides.

Intercolony Variation in Pesticide Detoxification by the Honey Bee (Hymenoptera: Apidae)

The aim of this book is to sound the alarm against dangerous tactics for controlling the pests that are an annoying but integral part of our world. Over 30 years after the devastation wrought by DDT, chemical pesticides are as pervasive as ever. The author argues that this ongoing commitment to pesticides reflects our sense of place in nature: embattled, beleaguered and driven to aggression. Here he seeks to show how a more measured and discriminating approach to pests, one based on management rather than obliteration, might serve us and the natural world much better. Case studies are used and take the reader from lawns and kitchens to farms and orchards, from insects and weeds to rats and coyotes. These show the complex political, biological, economic, social and personal interactions that lie behind each pest management decision. The diverse instances of pest management are considered, and reveal a consistent pattern of mistakes and problems. The author uses these to lead to a realistic, workable proposal for reducing pesticide use.

Mark L. Winston

Papers

The influence of wax deprivation on temporal polyethism in honey bee (Apis mellifera L.) colonies

Suppression of queen rearing in European and africanized honey bees Apis mellifera L. by synthetic queen mandibular gland pheromone

Semiochemicals influencing the host-finding behaviour of Varroa destructor.

Intercolony Variation in Pesticide Detoxification by the Honey Bee (Hymenoptera: Apidae)

Nature Wars: People vs. Pests