Root maggots (Delia spp., Diptera: Anthomyiidae) in prairie canola (Brassica napus L. and B. rapa L.): Spatial and temporal surveys of root damage and prediction of damage levels

Abstract

Soroka, J. J., Dosdall, L. M., Olfert, O. O. and Seidle, E. 2004. Root maggots (Delia spp., Diptera: Anthomyiidae) in prairie canola (Brassica napus L. and B. rapa L.): Spatial and temporal surveys of root damage and prediction of damage levels. Can. J. Plant Sci. 84: 1171-1182. The levels of infestation and damage to canola taproots caused by crucifer-feeding root maggots (Delia spp.)(Diptera: Anthomyiidae) were determined through surveys of commercial crops across the canola growing regions of western Canada. Canola root damage caused by Delia spp. maggots was measured at the end of the season by determining the percentage of plants infested (PPI) per field and estimating average damage levels (DL, on a scale of 0 to 5) to taproots. Over the course of the survey, 2890 canola fields were sampled. Infestation by root maggots occurred wherever canola is grown in western Canada. In the study, 96% of the fields surveyed in Manitoba and Saskatchewan and 99.8% of the fields in Alberta showed evidence of root maggot feeding, with PPI much higher than in provincial surveys of a decade previously. Geographical ecoregion significantly affected both PPI and DL. The greatest amount of damage over the largest area was found in western and northwestern Alberta, although localized areas with severely damaged roots occurred along the northern edge of the entire Parkland ecoregion. Over the entire survey area, Brassica rapa L. roots had greater PPI and DL than B. napus L. roots, although species differences were not significant in Saskatchewan or Manitoba. Data from the survey were correlated with weather variables to develop a model predicting the levels of damage inflicted by root maggots to canola roots. Of the weather variables investigated, temperature, especially the average temperature in the preceding July and August, had the greatest influence on PPI and DL. The warmer the temperatures of the preceding July and August, the lower the PPI and DL in the current year. Likewise, previous year's July and August precipitation influenced PPI and DL negatively. Other weather parameters had little consistent influence on PPI and DI. The predictive model for PPI and DL, developed from the 1995-1998 survey data, incorporated canola species, ecoregion, previous July-August and September-October temperatures and precipitation. The validity of the model was assessed using a set of survey data collected in Alberta from 1981 to 1983. Regression equations of predicted results on actual results were significant. However, r 2 values for the regressions were low, in part because of the few ecoregions surveyed and the lack of canola species data recorded in the earlier survey, and because of the large increase in infestation levels since the earlier data were collected. The study is a first step in forecasting the effects of root maggots across a wide geographic area featuring many different canola production practices. For personal use only.

Proton Transfer Reaction Mass Spectrometry: Applications in the Life Sciences

“…3.3); remaining frass and microbes alone therefore can not be responsible for the elevated sulfide emissions. This also precludes that root pathogens entering the roots at the damage sites have a major effect [128], as they would also remain after larval feeding has stopped. C6 wound compounds were not detected in our analyses, neither after insect damage nor after mechanical wounding.…”

Size doesn’t matter: The effects of seed size and seeding rate on injury by root maggots (Delia spp., Diptera: Anthomyiidae) to canola (Brassica rapa L. and B. napus L.)

“…Location also strongly affected maggot damage, with much more damage occurring on roots at Melfort than at Saskatoon (Table 1). Previous work has found greater maggot feeding in northern areas of Saskatchewan than in central or southern locations (Soroka et al 2004). …”

“…Weather, principally previous year temperatures (Soroka et al 2004) and current year precipitation (Turnock et al 1992), have been shown to greatly influence Delia biology. Location also strongly affected maggot damage, with much more damage occurring on roots at Melfort than at Saskatoon (Table 1).…”

“…can be a serious threat to canola (Brassica rapa L. and B. napus L.) production in parts of the Canadian prairies (Thomas 2003;Soroka et al 2004). Yield losses caused by root maggot feeding of up to 50% in B. rapa stands and 20% in B. napus stands have been reported (Griffiths 1991).…”

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

“…The root-feeding species of Delia RobineauDesvoidy (Diptera: Anthomyiidae) have become more widespread and injurious to canola (oilseed cultivars of Brassica napus L. and B. rapa L. (Brassicacae)) on the Canadian prairies as the area planted has increased (Soroka et al 2004). In regions of the prairies with more than 250 mm of rainfall from June to August, the cabbage maggot, D. radicum (L.), is the most abundant Delia species attacking canola (Griffiths 1986b).…”