Musca domestica L. (Houseflies)
Calliphora sp. (Blue Bottle Flies)
Two species of flies are used at NCRPIS to pollinate umbelliferous crops (e.g. Anethum, Angelica, Camelina, Crambe, Dalea, Daucus, Hyoscyamus, Petroselinum, Pimpinella, Spireae, Torilis) in field and greenhouse cages. Flies are used in approximately 40 greenhouse cages in the winter and about 20 greenhouse cages in the spring/summer; about 80 field cages are supplied with flies in the summer.
Flies are considered “incidental” pollinators. As they move around flowers in search of nectar, they move pollen on their body hairs from one flower to another. When flies are included with honey bees in cages containing the above mentioned plant species, pollination is more effective than when only honey bees are present (Wilson et al, 1991). An additional greenhouse study conducted in winter 2003 – 2004 at NCRPIS showed that Pimpinella seed viability from cages provided with either houseflies alone or both species of flies was comparable and greater than cages with blue bottle flies alone.
Flies will work plants at average temperatures of 70 to 90 F (21.5 to 32.5 C). Both species of flies may be less active in inclement weather; blue bottle flies may be less active at very warm temperatures. Flies are non-aggressive toward humans, but may be considered “irritating”. Rearing of flies is well established and pupae are low cost to purchase.
At NCRPIS, both species of flies are purchased as pupae from outside sources. Houseflies are purchased locally from an Iowa State University Entomology project; blue bottle flies are purchased from a commercial source in Idaho. House fly pupae can not be stored for an extended length of time, so a fresh supply is picked up weekly. Blue bottle fly pupae can be stored at 32 F (0o C) for three weeks before adult emergence is significantly reduced; regular shipments are scheduled at the beginning of each pollination season (winter greenhouse and summer field).
Based on past NCRPIS research, ca 200 fly pupae are placed in each cage weekly (Wilson et al, 1991). In general flies will live 2 to 3 weeks but weekly replenishment ensures an adequate population for pollination. Fly pupae are incubated for 2 to 3 days in 0.2 liter paper cartons with screened lids at 80 F (26.5o C) 30 % RH before placing in cages to ensure higher percent adult emergence. Fly pupae holders constructed of 0.9 liter plastic containers weighted with plaster are placed inside each cage to receive the pupae. Adult flies also may use these containers to rest in during the evening or inclement weather. No further care is provided to the flies once they are placed in the cages.
Wilson, R.L., M.P. Widrlechner, and K.R. Reitsma. 1991. Pollination methods for maintaining carrot germplasm collections. FAO/IBPGR Plant Genetic Resources Newsletter, 85:1-3.