Recycling of entomopathogenic nematodes in Delia radicum and in other insects from cruciferous crops

2005

Biocontrol

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The susceptibility of pupating larvae of pollen beetles, Meligethes spp. Stephens (Coleoptera: Nitidulidae) and brassica pod midges, Dasyneura brassicae Winnertz (Diptera: Cecidomyidae) to entomopathogenic nematodes (Nematoda: Rhabditida) was studied in the laboratory. The results showed that brassica pod midge larvae were almost unaffected by the tested nematodes (Steinernema bicornutum, S. feltiae and Heterorhabditis bacteriophora) whereas successful pupation of pollen beetle larvae was reduced with increasing number of nematodes (S. bicornutum, S. carpocapsae, S. feltiae and H. bacteriophora). The exposed larvae had been collected in the field and some of the pollen beetle larvae were parasitised by parasitoid wasps. It appeared that parasitised larvae were less affected by nematodes than non-parasitised larvae.

Section: Discussionsupporting

confidence: 92%

Susceptibility of Meligethes spp. and Dasyneura brassicae to entomopathogenic nematodes during pupation in soil

Nielsen¹,

2005

Biocontrol

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“…Entomopathogenic nematodes of the genera Steinernema (Rhabditida: Steinernematidae) occur frequently in cultivated soils (Burman et al ., 1986; Hominick & Briscoe, 1990a,b; Griffin et al ., 1991; Haukeland, 1993; Hominick et al ., 1995; Miduturi et al ., 1996; Nielsen, 2000). The nematodes may invade soil‐inhabiting insects and kill them within 48 h by the release of pathogenic bacteria.…”

Section: Introductionmentioning

confidence: 99%

Occurrence of Steinernema species in cabbage fields and the effect of inoculated S. feltiae on Delia radicum and its parasitoids

Nielsen¹,

Agri and Forest Entomology

2004

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1 Seven organically grown cabbage fields were surveyed for entomopathogenic nematodes in the autumn by baiting. Nematodes were obtained from three fields with bait larvae infection ranging from 1.3-4.0%. 2 Inoculation of Steinernema feltiae (Rhabditida: Steinernematidae) in the spring increased bait larvae infection to 16.0-32.0%. 3 Four different species were found (Steinernema affine, Steinernema bicornutum, S. feltiae and Steinernema C1). 4 The number of Delia radicum (L.) (Diptera: Anthomyiidae) puparia was significantly reduced at plants where S. feltiae had been inoculated. 5 Delia radicum parasitoids were also affected by S. feltiae. The results indicated that Aleochara species (Coleoptera: Staphylinidae) were more negatively affected than Trypliographa rapae (Westw.) (Hymenoptera: Cynipidae).

“…Pea was the crop with the greatest number of insects (S. lineatus) and this resulted in both years in high incidences of nematodes in autumn. It is known from other studies that S. lineatus is highly susceptible to entomopathogenic nematodes (Jaworska & Ropek, 1994) and one weevil larvae of the size of S. lineatus can produce 1000-2000 infective juveniles (Nielsen & Philipsen, 2004b). Also cabbage root flies are potential hosts of entomopathogenic nematodes (Nielsen, 2003;Nielsen & Philipsen, 2004b), but the level of these insects was relatively low in the study and the growing of cabbage had only a minor positive effect on nematode incidence.…”

Section: Discussionmentioning

confidence: 72%

Seasonal population dynamics of inoculated and indigenous steinernematid nematodes in an organic cropping system

Nielsen¹,

2004

Nematol

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This study was based on naturally occurring and inoculated populations of steinernematid nematodes. The nematode populations were monitored in spring and autumn in 2 consecutive years in an organic cropping system and changes in population size were related to the presence of potential insect hosts. Nematode populations were estimated in terms of nematode incidence (percentage of positive soil samples) by using Tenebrio molitor larvae as bait. The population of naturally occurring nematodes (Steinernema affine and S. feltiae) was generally low (0-17% incidence for S. affine and 0-18% incidence for S. feltiae). Inoculated S. feltiae established well in half of the plots where inoculation had been performed and reached incidences of 87%. Establishment of inoculated nematodes, and population dynamics in general, was clearly influenced by the presence of insect hosts. In crops with high densities of potential hosts (Sitona lineatus in pea and partly Delia radicum in cabbage), nematode incidence increased from spring to autumn, whereas nematode incidence remained unchanged or decreased when few hosts were present (in barley, carrots, alfalfa and leek).