Potential application of the bumblebee foraging recruitment pheromone for commercial greenhouse pollination

Apidologie, Jul 2018

Commercial bumblebee colonies are important crop pollinators. Here we assess whether application of artificial foraging recruitment pheromone can increase foraging activity in Bombus terrestris colonies on a relevant timescale for commercial pollination. We measured bee traffic from the nest to a foraging arena, which is correlated with foraging activity under natural recruitment conditions. During continuous pheromone exposure bee traffic increased by 1.5 to 3.6 times, and this increase lasted up to 105 minute. Repeated 20 minute exposures of a colony to recruitment pheromone, with at least 30 minutes intermissions, triggered consistent traffic increases over a four week period. We conclude that artificial recruitment pheromone can reliably boost bee traffic leaving previously inactive colonies. This method could improve foraging activity and pollination in greenhouse colonies, especially young colonies reluctant to start foraging after introduction to the crop.Kommerziell erhältliche Hummelkolonien sind wichtige Bestäuber verschiedener Nutzpflanzen. Diese Hummelkolonien werden jedoch von den Lieferanten mit grossen Nektarbehältern verschifft, und dieses Überangebot kann die Motivation der Hummeln zur Sammeltätigkeit einschränken, was wiederum den Ertrag der Nutzpflanzen beinträchtigt. Kürzlich wurde das Pheromon identifiziert, welches Hummelarbeiterinnen zur Sammeltätigkeit stimuliert. Hier wird untersucht, ob eine künstliche Mischung der wesentlichen Komponenten des Pheromons (Eukalyptol, Ocimen und Farnesol) die Sammeltätigkeit von Hummeln (Bombus terrestris) über Zeitskalen verbessern kann, wie sie für die kommerzielle Bestäubung angemessen sind. Die Aktivität der Kolonien wurde gemessen, indem die Zahl der Arbeiterinnen bestimmt wurde, die während eines Zeitintervalls das Nest verliessen, um eine Flugarena zu erreichen. Nistkästen mit sechs Kolonien von Bombus terrestris dalmatinus (Dalla Torre) wurden jeweils mit einer Flugarena verbunden. Die Bewegungen der Tiere vom Nest zur Arena wurden während Kontrollintervallen oder Tests unter Pheromoneinfluss quantifiziert. Im ersten Experiment wurde die Dauer des Pheromoneffekts bestimmt, indem die Kolonien (nach einer Kontrolle von 30 Minuten ohne Pheromon) für 120 Minuten dem Pheromon ausgesetzt wurden. Im zweiten Experiment wurde die minimale Dauer bestimmt, die zwischen zwei Pheromonexperimenten liegen muss, um beim zweiten Test noch einen messbaren Effekt zu erzielen (20 Minuten Kontrolle; danach 20 Minuten Pheromongabe; danach 30, 50 oder 70 Minuten Pause, und schliesslich nochmals 20 Minutes Pheromongabe). Das zweite Experiment erlaubte uns, zu testen, ob die wiederholte Gabe des Pheromons über die Dauer eines Monats zu einer Abnahme des Effektes führt. Während der kontinuierlichen Pheromongabe nahm der Hummelverkehr um einen Faktor von bis zu 3,6 zu, und diese Zunahme hielt für bis zu 105 Minuten an (Abb. 1). Die wiederholte Gabe des Pheromons war effektiv, sogar wenn die Pause zwischen zwei Tests nur 30 Minuten betrug. Der Effekt der zweiten Pheromongabe war jedoch im Mittel 32 % niedriger als der der ersten (Abb. 2). Die wiederholte Stimulierung der Kolonie über mehrere Wochen führte nicht zu einer Abnahme des Effekts (Abb. 3). Unsere Studie legt nahe, dass das künstliche Pheromon verlässlich die Aktivität von inaktiven Hummelkolonien steigern kann, besonders bei jungen Kolonien, bei denen der Aktivitätsbeginn manchmal verzögert ist. Es bleibt jedoch zu zeigen, das solche Aktivitätssteigerungen tatsächlich den Nutzpflanzenertrag verbessern.

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Potential application of the bumblebee foraging recruitment pheromone for commercial greenhouse pollination

Apidologie Potential application of the bumblebee foraging recruitment pheromone for commercial greenhouse pollination* Mathieu Mol 0 Lars C 0 Nigel E. R 0 0 Queen Mary University of London, Research Centre for Psychology, School of Biological and Chemical Sciences , Mile End Road, London E1 4NS , UK 1 Manuscript editor: Jacqueline Pierre - Commercial bumblebee colonies are important crop pollinators. Here we assess whether application of artificial foraging recruitment pheromone can increase foraging activity in Bombus terrestris colonies on a relevant timescale for commercial pollination. We measured bee traffic from the nest to a foraging arena, which is correlated with foraging activity under natural recruitment conditions. During continuous pheromone exposure bee traffic increased by 1.5 to 3.6 times, and this increase lasted up to 105 minute. Repeated 20 minute exposures of a colony to recruitment pheromone, with at least 30 minutes intermissions, triggered consistent traffic increases over a four week period. We conclude that artificial recruitment pheromone can reliably boost bee traffic leaving previously inactive colonies. This method could improve foraging activity and pollination in greenhouse colonies, especially young colonies reluctant to start foraging after introduction to the crop. 1. INTRODUCTION Bumblebees are important pollinators used extensively for pollination of greenhouse commercial crops such as tomato, sweet pepper and avocado (Dasgan et al., 2004; Roldan Serrano and Guerra Sanz, 2006; Ish-Am et al., 1998; Velthuis and van Doorn, 2006) . Commercial bumblebee nest-boxes contain an ad libitum artificial nectar reservoir to feed the colony during transport from bee breeder to crop grower. These nectar feeders remain inside the colony even after they have been placed in greenhouses because many crop plants, e.g. tomato, produce no nectar (McGregor, 1976). The reservoir in the nestbox provides the colony with nectar, thus the number of full honeypots is always high. Overfeeding colonies with nectar in greenhouses could constitute a problem because it can decrease overall worker motivation to forage, as shown in laboratory conditions by Molet et al. (2008) . Indeed, in colonies with large nectar reserves stored in honeypots, successful foragers make fewer excited recruitment runs when they come back to the nest, and nonforaging workers are less responsive to nectar influx to the honeypots as a cue to initiate foraging (Dornhaus and Chittka, 2005) . Commercial bumblebee colonies are not provided with pollen in their nest-box so they have to forage for this essential resource from the crop plants. In contrast to honeybees, an individual bumblebee forager often collects both nectar and pollen during a single foraging trip; their propensity to focus on collecting one or the other resource is affected by supply and demand (Plowright et al., 1999) and also environmental conditions (Peat and Goulson, 2005) . Hence a reduction in motivation to forage for nectar is also likely to affect pollen foraging. Thus decreased motivation to exit the nest will probably lower rates of flower visitation, reducing pollination success and ultimately crop yield and quality. However bumblebee breeders or glasshouse crop growers cannot limit food supplies to colonies with a view to increasing their motivation to forage because the risks of colony mortality by starvation would be high since bumblebees only store a few days worth of food. Instead, growers buy larger numbers of colonies than might be needed if bees were fully motivated to forage. The recruitment of non-foraging bumblebee workers by successful foragers returning to the nest with nectar relies on the release of a recruitment pheromone (Dornhaus et al., 2003) . The major components of this pheromone (eucalyptol, farnesol and ocimene) have been shown to produce short term increases in foraging activity when applied singly (Mena Granero et al., 2005) or in combination (Molet et al., 2008) . Although the effectiveness of this pheromone is reduced when colonies have large nectar reserves, applying the artificial pheromone (a combination of eucalyptol, farnesol and ocimene) to such well-fed colonies can increase the number of foragers by 60% and the number of foraging bouts by 40% during a 30 minutes period after pheromone application (Molet et al., 2008) . These results suggest that artificial recruitment pheromone could be applied to commercial colonies in greenhouses to trigger an increase in foraging activity. Here we explored whether the artificial pheromone technique could be used to enhance colony foraging activity over long periods. We measured bee traffic from the nest to a foraging arena as a proxy measure of foraging activity because traffic and actual foraging activity are correlated (Kwon and Saeed, 2003; see discussion) . Therefore, we tested the efficiency of an artificial pheromone mixture at increasing bumble (...truncated)


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Mathieu Molet, Lars Chittka, Nigel E. Raine. Potential application of the bumblebee foraging recruitment pheromone for commercial greenhouse pollination, Apidologie, pp. 608-616, Volume 40, Issue 6, DOI: 10.1051/apido/2009034