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

Abstract

The drone fly (Eristalis tenax) pollinates many crops and is found almost worldwide. Its successful management as a field-crop pollinator would provide an additional option to augment bee pollination. We reviewed literature to assess their management potential. A literature search was conducted for information on drone-fly abundance across New Zealand crops, pollinator effectiveness, lifecycle-requirements and potential for mass rearing. Relevant literature was then evaluated to assess the feasibility, benefits and limitations of their management. Eristalis tenax is a proven pollinator of pak choi (Brassica rapa spp. chinensis), kiwifruit (Actinidia deliciosa) and onion (Allium cepa), and visits the flowers of several more crops in New Zealand. It readily completes its lifecycle under laboratory conditions when reared on various organic materials. No reviewed studies were identified that showed successful management of populations for the purpose of field-crop pollination. Key challenges for their management as field-crop pollinators include: being able to mass rear them at an appropriate scale; retaining numbers within targeted areas in the field; and ensuring their use does not significantly impact on non-target species and land-user interests.

The Role of Flies as Pollinators of Horticultural Crops: An Australian Case Study with Worldwide Relevance

“…In these crops, it displays pollination efficiency traits similar to honey bees in terms of pollen loads carried [38] and stigmatic pollen deposition [41], but it also crosses more readily between hybrid parent lines than honey bees [51]. However, while E. tenax has been demonstrated to pollinate field crops and displays some life cycle, physical and behavioural attributes desirable for mass rearing on cheap and easily obtained substrates, specific information relating to its management as a field crop pollinator is currently lacking [58].…”

“…Syrphid activity is impacted by cloud cover, wind and rain, seemingly to a greater extent than for most blow flies (which are generally larger in body size). Regardless, E. tenax actively forages at temperatures as low as 5 • C [58]. Temporal variation in foraging activity will occur across species and families and, for potential pollinating agents, must be assessed alongside the timing of target crop flowering.…”

“…Rearing protocols have been established for E. tenax with adults maintained on nectar and pollen, while the larvae can be successfully reared on a diet of decomposing organic matter such as cow manure [58,172]. However, the larvae are aquatic, breeding in liquid substrates of decaying organic matter, including wet decaying seaweed, stagnant water bodies polluted with manures, human sewage and decomposing animal carcasses [58]. The posterior spiracles of the aquatic larvae of E. tenax are located on a retractable caudal segment that, extended (up to three times the length of the larvae), provides a breathing tube allowing larvae to obtain air from the surface of a water body while submerged.…”

“…As with calliphorids, the development of syrphids can be manipulated by temperature control to facilitate the synchronisation of pupation and emergence with transport and application timing [206]. [58,171,172]. Reproductive output is high, with lifetime fecundity reported at 3,000 eggs/female [172].…”

“…Upon release, syrphids such as E. tenax are capable of travelling up to 75 km a day, but foraging opportunities and physiological status direct flight activity and dispersal [58]. The adult life span upon release is dependent on species, temperature and nutritional intake ( Table 2).…”