|scientific name Delia radicum |
It is a major pest of Cruciferae crops and it is confined to gardens and cultivated lands.
Appears to be one to two generation a year in Alberta with emergence from overwintered puparia spread from mid May to mid July.
Delia radicum may be distinguished from other Delia species occurring in the field by the following combinations of characters: Adults look similar to house flies but are smaller (5mm), dark ash grey color with a dark stripe along the top of the abdomen, and covered with black hairs and bristles (setae).The reddish purple eyes on males nearly touch in the centre of the head while female eyes are separated. In males, the presence of the basal brush of long setae (anteroventral setae) on the hind femur and by relatively shorter lateral setae of the 5th sternite processes. In females, in the hind femur, the row of anteroventral setae is normally uneven and posteroventral setae are lacking.
Adults are found from late spring to late October flying close to the ground in search of suitable host plants. Flies emerge in the spring from overwintering puparia and feed on the nectar of wild flowers. They mate and females begin egg laying about a week after emerging. During their 5-6 week life span, females lay eggs singly or in masses at or near the stems of host plants on cool, moist soil. Depending on temperature, maggots hatch in 3-10days and commence feeding on small roots and root hairs and then tunnel in to the main roots. They mature in about 3-4weeks, then leave the roots and pupate in puparia about 5-20cm deep in the soil. Adult flies emerge in 2-3 weeks, mate, lay eggs, and repeat the cycle
Not of concern.
Larvae are notorious root maggots infesting all forms of cultivated cruciferous crops. The larvae can also be found on certain cruciferous weeds among which stink weed (Thlaspi arvense L.) is particularly important in Alberta as cited by Griffiths( 1986).
Holarctic. Delia radicum can be found through out Canada, where cultivation of cruciferous crops is undertaken.
As cited by Griffiths (1991), Delia radicum (Linnaeus) is included under Delia radicum subsection along side with Delia planipalpis (Stein) and Delia floralis (Fallen). There was much confusion in the past regarding the identity of Delia radicum root maggots. Many synonyms were used. Examples: Anthomyia brassicae Bouche; Anthomyia raphani Harris; Hylemyia brassicae (Bouche), etc. Currently many studies are undertaken by entomologists to enhance and conserve the natural enemies of Delia radicum belongs to families of Carabidae and Staphylinidae of order Coleoptera and family Cynipidae of order Hymenoptera in various cropping systems in particular canola cropping system to produce sustainable pest management programme Canada.
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