An Improved Rearing Procedure for the Carrot Rust Fly (Diptera: Psilidae) With Observations on Life History and Conditions Controlling Diapause Induction and Termination

Abstract

Carrot rust fly (CRF), Psila rosae (Fabricius) (Diptera: Psilidae), caged with 2-month-old carrot plants at 20 °C, 50–70% RH, and 16:8 L:D laid an average of 109 eggs per female. With ca. 50% survival from egg to pupae, the rearing procedure yielded a 25 × population increase per generation. The duration of the life cycle at 20 °C was ca. 65 days. Calculated threshold temperatures and degree days above those temperatures necessary for complete development were: eggs, 4.5 °C and 94 degree days (°D); larvae, 2.02 °C and 625 °D; and pupae, 1.47 °C and 374 °D. Larvae collected in the field in fall developed normally when incubated at 22 and 19 °C; ca. 40% of the pupae entered diapause at 16 °C, and 100% at 13 and 10 °C. Fall-collected larvae chilled at 1 °C for ca. 3 months developed normally at all temperatures including those which induced diapause in pupae from unchilled larvae. With laboratory-reared pupae, 100% diapause was induced with > 10 days exposure to 13 or 10 °C. Twenty weeks storage at 1 °C was sufficient to terminate diapause in > 95% of the pupae. The ability of both CRF larvae and pupae to survive cold temperature conditions suggests that 2 separate spring emergence peaks may occur, which could have important implications if the spring flight is to be predicted on the basis of °D accumulations.

Development of the overwintering stages of the carrot fly, Psila rosae (Diptera: Psilidae)

“…In the present study, it was estimated that diapause was completed after 270 days at 5°C and after 180 days at 7°C. These quantitative estimates agree with the earlier qualitative estimates (McClanahan & Niemczyk, 1963;Brunei & Missonier, 1968;Stadler, 1970;Burn & Coaker, 1981) that more than 200 days of 'cold' treatment are required to reduce the time for development of diapausing pupae to the 21-25 days required for the development of non-diapausing pupae (McLeod et al, 1985;Van't Sant, 1961). In the present study, development times, and thus by inference the intensity of diapause, reached a maximum of about 55 days after 80 days of 'cold' treatment.…”

“…response to low temperatures. This finding was confirmed by Burn & Coaker (1981) and McLeod et al (1985). However, Brunei & Missonier (1968) showed that sensitivity to low temperatures increased from late summer to autumn and that the percentage of insects entering diapause increased from early July to late August.…”

“…The mean time for adults to emerge ranged from 114 + 27 days at 9°C to 44 + 9 days at 21.5°C. Similar data from a Canadian (Ontario) population of P. rosae (McLeod et al, 1985) are shown for comparison ( fig. 6-Line 2), though in the Canadian situation, the pupae were collected in October as the ground is generally frozen solid in February.…”

“…6-Line 3). Data for larvae pre-chilled at 1°C for 97 days are shown for the Ontario population (McLeod et al, 1985) ( fig. 6-Line 4).…”

Effect of pre-wintering and wintering temperature regimes on weight loss, survival, and emergence time in the mason bee Osmia cornuta (Hymenoptera: Megachilidae)

“…The time to emerge after exposure to warm temperatures is inversely related to the duration of the cold exposure period, a pattern that has been described for numerous temperatezone winter-diapausing insects (e.g. Neilson, 1962;McLeod et al, 1985;Bell, 1989;Wang and Laing, 1989;Denlinger and Tanaka, 1999). Although in some insect species diapause may alternatively be completed without chilling (Danks, 1987;Hodek and Hodková, 1988), individuals of both Osmia species chilled for less than 90 days have low survival, protracted emergence periods and are less vigorous after emergence.…”