Pollinator-friendly practices to enhance crop production in apples and pears

GARIBALDI, LUCAS A.; GESLIN, BENOIT; AIZEN, MARCELO A.; GARCIA, NANCY; LE FÉON, VIOLETTE; PEREIRA, ANA J.; VASSIÈRE, BERNARD E.

Ribeirão Preto

Congreso; Simpósio: Abelhas na Interface da Agricultura e Conservação, XI Encontro sobre Abelhas; 2015

Deployment of honey bee (Apis mellifera) colonies in cultivated fields is a widely used management practice to enhance crop yield through pollination. However, worldwide the stock of domesticated honey bees is growing slower than the agricultural demand for pollination which could lead to a current or future mismatch between supply and demand. We thus need to develop friendly managing procedures that can enhance the effectiveness of bees to pollinate crops. Honey bees are the most commonly used bee to pollinate a wide array of crops globally, however their contribution to crop yield quantity and quality remains largely unknown for most crops. We studied the pollination of pear and apple (the first and third most exported fruit by weight in Argentina, respectively) in the main fruit producing area of Argentina (Neuquén region, North Patagonia) and the impact of pollinator management on fructification. During the flowering of 2014, we sampled 88 trees of apples and pears distributed across 24 farms, from pollination to fruit set and harvest quality. In half of the farms, we installed high quality colonies of Apis mellifera, which were previously prepared following a standard protocol. These colonies were free of American and European foulbrood, with a rate of Varroa infestation <5% (based on worker sealed brood), and a laying queen with a population of at least 15 000 workers. The remaining farms received honey bee colonies without any specific qualitycontrol. We thus studied the effects of crop and colony management on bee visitation and behaviour, fruit set, and fruit yield and quality (circumference, height, weight, number of seeds, and sugarconcentration). The pollination process relied solely on managed honey bees as we did not observe any wild pollinator visiting pear or apple flowers during our whole survey. Fruit set was positively influenced by the visitation rate (number of visits/100 flowers/minute), which in turn was related to both colony number and quality. Trees that were located in farms supplied with high-quality colonies received significantly more visits. High visit frequency was also related to changes in bee foragingbehaviour that resulted in higher pollination effectiveness of single visits. The fact that pollination process relied solely on Apis mellifera is of great concern because of the high vulnerability of such a simple pollination network. Yet our study depicts a situation that might become widespread in the future if wild bee populations continue to decline, with the service of pollination relying on honey bees only. We discuss these results in regards to economic costs and benefits for farmers. In the future,we will launch several studies (including the introduction of a local bumblebee species) in order to provide alternative and complementary practices to achieve more sustainable pollination in this region.