Steinernema affine (Nematoda: Steinernematidae), a new record for North America and its distribution relative to other entomopathogenic nematodes in British Columbia

Randomly selected ecosystems in the coastal Greater Vancouver, Fraser valley and southern Vancouver Island regions, and in the interior Okanagan region of British Columbia, were sampled for the presence of entomopathogenic nematodes (EPN). Of 133 soil samples, 23 contained EPN (18 with steinernematids and five with heterorhabditids). Three identified species and one unidentified species were found. Steinernema affine and S. kraussei occurred in most EPN positive locations in the coastal regions sampled. Steinernema affine was found in open habitats and S. kraussei in all types of tree habitats. Steinernema feltiae was found in only one location, White Rock, in the Greater Vancouver region, close to an ocean beach. Heterorhabditis megidis occurred in only the drier Okanagan valley region of central, southern British Columbia, which has a more extreme climate than the moist, moderate climate of the coastal region. It occurred mostly in agricultural land represented by orchards, vineyards, and secondary woodland. In field baiting and laboratory experiments S. affine appeared to be a more successful parasite than S. kraussei.

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

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).

Susceptibility of cabbage root fly Delia radicum, in potted cauliflower (Brassica oleracea var. botrytis) to isolates of entomopathogenic nematodes (Steinernema and Heterorhabditis spp.) indigenous to the UK

The susceptibility of larvae of the cabbage root fly (Delia radicum) to ten isolates of entomopathogenic nematodes was examined in a glasshouse experiment using cauliflower (Brassica oleracea var. botrytis) as the host plant. Steinernema affine Horticulture Research International (HRI) code 179 provided the highest level of control, killing approximately 46% of the cabbage root fly within 28 days. Two Heterorhabditis isolates (HRI code K122 and UK211) and Steinernema E1 and F1 (HRI code 194 and GWE63) did not give any significant control. In a second experiment, S. affine was applied against cabbage root fly larvae at 8000 to 64 000 nematodes per pot, and its performance was compared to identical dose applications of Nemasys®, a commercial formulation of S. feltiae. Averaged over the four dose rates, S. affine controlled significantly more cabbage root fly (36%) than Nemasys® (10.4%).

Occurrence and distribution of entomopathogenic nematodes in the Slovak Republic

Infective-stage juveniles of entomopathogenic nematodes of the genera Steinernema and Heterorhabditis were recovered by direct extraction from 36% of a total of 111 soil samples collected in various biotopes from different regions of Slovakia. The rate of prevalence was highest in forest soil (58%). On the basis of morphological characters of the infective juveniles eight Steinernema and one Heterorhabditis species were distinguished. Steinernema affine, S. intermedium and S. feltiae were most prevalent (together 74% of all records). The other species of Steinernema encountered were S. kraussei, S. carpocapsae, S. bicornutum, a species of the S. glaseri group and an undescribed species earlier recorded from Germany. In 11 of the 40 soil samples positive for entomopathogenic nematodes mixtures of two to four species were present. Several species showed a distinct habitat preference, e.g., S. affine for arable soil and S. intermedium for woodland and river bank vegetation with trees. A preference for certain soil types was less apparent. Untersuchungen uber Vorkommen und Verbreitung entomopathogener Nematoden in der Slowakischen Republik - Insgesamt 111 Bodenproben, die in unterschiedlichen Biotopen aus verschiedenen Regionen der Slowakei entnommen worden waren, wurden auf entomopathogene Nematoden untersucht. Infektionsjuvenile der Gattungen Steinernema und Heterorhabditis waren uber eine direkte Extraktion der Nematoden aus dem Boden in 36% aller Proben nachweisbar. Der hochste Anteil "positiver" Proben fand sich bei Proben aus Waldern (58%). Anhand morphologischer Merkmale der Infektionsjuvenilen waren acht Steinernema Arten und eine Heterorhabditis-Art differenzierbar. Steinernema affine, S. intermedium und S. feltiae waren die haufigsten Arten (insgesamt 74% aller Nachweise). S. kraussei, S. carpocapsae, S. bicornutum, eine Steinernema-Art der S. glaseri-Gruppe und eine noch unbeschriebene Steinernema-Art (bereits aus Deutschland bekannt) und Heterorhabditis sp. wurden seltener gefunden. In 11 aller 40 "positiven" Proben kamen zwei bis vier Arten nebeneinander vor. Einige der Arten zeigten eine deutliche Bevorzugung bestimmter Biotoptypen, so S. affine von Acker- und Gartenboden und S. intermedium von Waldern und Ufervegetation mit Baumen. Eine Bevorzugung bestimmter Bodenarten war dagegen kaum erkennbar.