Emergence Patterns of Delia radicum (Diptera: Anthomyiidae) Populations from North Carolina and New York

Abstract

Cabbage maggot, Delia radicum (L.), populations from North Carolina (Fletcher and Scaly Mountain) and New York (Geneva and Highland) were surveyed to detect differences in the emergence pattern of flies from overwintered pupae. Populations from all locations consisted of different proportions of early-and later-emerging individuals. However, populations from New York consisted predominately of early-emerging individuals (~90%), whereas populations from North Carolina were composed of a higher percentage oflater-emerging individuals. Emergence patterns of F1 progeny from crosses between early-and later-emerging flies from Scaly Mountain demonstrated that emergence traits were genetically controlled. D. radicum phenology studies in North Carolina suggested that temporal isolation of the two types was halted by an extended period of aestivation during the summer months, which subsequently allowed the two populations to interbreed during the autumn months. The relative proportion of early:late emergers appears to be unstable over time, which may be due to differential mortality factors operating when populations are temporally isolated or due to dominance or recessive factors governing earliness or lateness, or both.

Spring Emergence and Seasonal Flight ofDelia radicumL. (Diptera: Anthomyiidae) in Western Oregon

“…An increase in adult activity near the end of August has also been observed by other researchers (Walgenbach et al 1993). It is unknown whether the beginning of the fall ßight is triggered by declining temperatures, shortening of photoperiod, onset of fall rains, sufÞcient degree-day accumulation for full physiological development of the fall population, change in the quality of host plants, other environmental factors, or some combination of these.…”

“…North Carolina, where 47Ð71% of ßies emerging in 1987Ð1990 were in the early peak (Walgenbach et al 1993). Biron et al (2003) also reported a predominance of early-emergers (71.4%) in their study of D. radicum in Finland.…”

“…gions around the world have reported a bimodal spring emergence pattern, with distinct early and late peaks, that extends over several months (Read 1958, Walgenbach et al 1993, Biron et al 2003. After emergence, ßies feed on protein and carbohydrate sources such as ßowering fruit trees and other nectar-producing plants before mating (Harris andSvec 1966, Finch andCoaker 1969), which occurs within 4 Ð 6 d of emergence (Swailes 1961).…”

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

“…At the intrapopulation level, D. radicum phenotypes with rapid, intermediate, and slow development can be readily selected in the laboratory Walgenbach et al 1993;Biron et al 1998). It is hypothesized that two phenotypes persist because the early phenotype can complete more generations in warm years and the late phenotype is safer in extreme spring weather that may kill earlyemerging adults before they can reproduce Walgenbach et al 1993;Biron et al 1998). The positive correlation between the proportion of the early phenotype in a locality and thermal accumulation during the previous growing season supports this hypothesis (Turnock and Boivin 1997).…”

Reduction of Delia radicum attack in field brassicas using a vertical barrier

“…Delia radicum (L.) (Diptera: Anthomyiidae, Anthomyiinae, Hydrophoriini), known as the cabbage maggot (CM) in North America and cabbage root fly in the UK, is a major and chronic threat to the commercial production of brassica crops in the temperate northern hemisphere (Getxin, 1985;Walgenbach et al, 1993;Dalthorpe & Dreves, 2008). In Canada and elsewhere, growers have typically applied granular and/or drenched insecticides to the soil, timed according to various routine prophylactic schedules, but the number of available insecticides for CM control has diminished greatly over the past decades (Vernon & Mackenzie, 1998).…”