Native and introduced bee abundances on carrot seed crops in New Zealand

Abstract

In New Zealand, unmanaged bees species can be important crop pollinators, but their abundance and distribution is poorly known within hybrid carrot seed crops. Standardised counts of bees visiting flowering carrot umbels (1350 umbels observed/field) across 19 commercial hybrid fields were conducted between 1000 h and 1500 h. Despite honey bees being observed in all fields, abundance varied greatly between fields (mean=98.1; maximum=330, minimum=1). Other bees observed visiting umbels were Lasioglossum sordidum (17 fields; mean=14; maximum=65); Leioproctus sp. (12 fields; mean=2.0; maximum=19); Hylaeus sp. (one field; maximum= 1) and Bombus terrestris (six fields; mean=2.0; maximum=11). The number of individual bees (all species together) counted/ umbel on male fertile umbels was significantly higher than on male sterile umbels, a factor that could contribute to sub-optimal pollen flow between umbel lines by bees. Examination of their movements between male fertile and sterile lines is required to verify their efficiency as pollinators.

Are insect flower visitor assemblages distinguishable between Brassica napus and B. rapa?

“…sativus (L.) Dominand) (Evans et al 2011), honey bees (A. mellifera), bumblebees (Bombus terrestris), and the native bees (L. sordidum and Leioproctus sp.) visiting carrot (Howlett et al 2015). However, when single varietal crops are grown in separate fields as in this study, local site factors can be the more important in influencing flower-visitor assemblage composition in at least some circumstances.…”

“…Insects were classified into the families Apideae (bees); Diptera (flies); Coleoptera (beetles); and Lepidoptera (butterflies and moths). We only considered insects as flower visitors if they had previously been identified as such within other New Zealand crops including Daucus carota (Howlett et al 2015), Actinidia deliciosa (Howlett et al 2017b), Persea americana, Allium cepa, Brassica rapa (Howlett et al 2009a). These were then counted from each trap sample.…”

“…Schübl. & G. Martens (Howlett et al 2015), kiwifruit (Howlett et al 2017b) and avocado (Read et al 2017). Moreover, at least some of these bee and non-bee pollinators have been shown to consistently move between a flowering crop and the surrounding environment (Mesa et al 2013) and carry viable pollen over distance of at least 400 m (Rader et al 2011).…”

The potential management of the drone fly (<i>Eristalis tenax</i>) as a crop pollinator in New Zealand

“…For example, drone flies may be a more efficient pollinator of hybrid vegetable seed crops than honey bees as they will more readily move between hybrid lines (Gaffney et al 2018). This movement is necessary to transport pollen from male fertile to male sterile umbels (Howlett et al 2015). There is also potential for crop growers to rear them en-masse on readily available substrates, including effluent or decaying plant material.…”

Insect flower visitors of planted native species within the arable landscape on the Canterbury Plains, New Zealand

“…chinensis (Howlett et al 2009), onion Allium cepa (Howlett et al 2005), carrot Daucus carota subsp. sativus (Howlett et al 2015), and radish Raphanus ativus (Howlett et al 2013b). Native bees, bumblebees and several fly species have been verified as pollinators of pak choi (Howlett et al 2011;Rader et al 2009), onion (Howlett et al 2017), carrot (Howlett 2012) and other vegetable seed fields in Canterbury (B. Howlett unpublished data).…”