A method for the continuous rearing of the cabbage root flyErioischia brassicae(Bch.) and some observations on its biology

Abstract

A method for continuously rearing cabbage root fly, Erioischia brassicae (Bch.) is described.Adult flies fed on sucrose, brewers’ yeast and yeast hydrolysate laid an average of 220 eggs per female when caged together in large numbers and 376 eggs per female when caged singly. Egg viability was 86 per cent. Egg hatch was severely reduced by relative humidities of less than 90 per cent, and the embryo became more susceptible to desiccation as it matured. The larvae were reared on swede, and maximum survival was obtained when the swedes were inoculated with an optimum number of eggs calculated from the ratio of 1 egg: 1.6 g. of swede. Different ratios were obtained from turnip and winter radish indicating that survival was probably related to the nutritional value of the rearing medium as well as to its availability. An average of 68 per cent, of the eggs placed on swede produced pupae that were equivalent in size to wild pupae. The fecundity of the flies was directly related to pupal weight and to the availability of protein in their diet. Adult longevity was reduced more by mutual disturbance than by any other factor.

Antibiosis resistance against larval cabbage root fly, Delia radicum, in wild Brassica-species

“…The proportions of successfully developing larvae and pupae are commonly used to assess the level of antibiosis resistance to D. radicum (Finch and Ackley 1977;Ellis et al 1999;Jyoti et al 2001;Felkl et al 2005). In the field experiment we collected larvae and pupae from the soil around the root system.…”

“…Green Comet. In the study of Finch and Ackley (1977), 18 and 38 % of inoculated eggs produced pupae on B. oleracea when infested at different plant ages. The papers cited above used 10-20 eggs for infestation.…”

“…They also found that B. macrocarpa and B. villosa were moderately resistant and all the tested B. oleracea accessions and cultivars were highly susceptible. In their study all accessions tested were accepted for oviposition, indicating that antixenosis is not always associated with antibiosis resistance (Finch and Ackley 1977;Wiklund 1975). Jyoti et al (2001) found antibiosis resistance in Sinapis alba, reducing weight and survival of larvae, pupae and adults of D. radicum.…”

“…In Western Europe and North America, economic losses due to root fly damage have been estimated to amount up to $100 million in some years. Furthermore, cabbage root fly infestations cause substantial yield losses in various other Brassica crops including broccoli, cauliflower, turnip, and rutabaga (Finch and Ackley 1977).…”

Spring emergence of CanadianDelia radicumand synchronization with its natural enemy,Aleochara bilineata

“…The predicted intervals between emergence of A. bilineata and prairie D. radicum suggest that emergence of A. bilineata on the prairies is well synchronized with availability of prey. Under optimal conditions, four or five days elapse between emergence of adult female D. radicum and commencement of oviposition (Finch 1974), and the oviposition rate is high for two-three weeks thereafter (Swailes 1961;Finch and Coaker 1969). Eggs hatch four2five days after oviposition (Finch and Coaker 1969).…”