Search

Entomopathogenic nematode species perform differently under different environmental conditions; therefore, the authors investigated the biological and environmental characteristics that could optimize performance of Steinernema innovationi. The authors studied the effect of temperature on infectivity and reproduction, the foraging behavior and host range. Thermal activity was optimal between 22 and 25°C. Highest infective juvenile (IJ) yields in last instar Galleria mellonella were observed at 22°C (333,014 IJs/g) and 25°C (354,165 IJs/g). An average of 26% of the IJs infected G. mellonella larvae at depths of 15 cm within 24 hr. Steinernema innovationi IJs raised greater than 95% of their body off the substrate and moved in a circular pattern, but did not jump. The hosts, Acheta domesticus, Chilo partellus, and Plutella xylostella showed the least susceptibility. All other hosts, [Eldana saccharina, Sesamia calamistis, Tenebrio molitor, G. mellonella, Cydia pomonella] suffered 100% larval mortality. Pupal mortality ranged from 47 to 68%. An LC50 and LC70 of 3 and 31 IJs/larva, respectively, were calculated for Agrotis ipsilon. The results indicate that S. innovationi is adapted to moderate temperatures. Furthermore, to the author's knowledge this is the first report of a nematode (particularly from 'glaseri group') that shows cruiser-type behavior in movement, but also nictates. [ABSTRACT FROM AUTHOR]

A new species of entomopathogenic nematode (EPN), Steinernema biddulphi n. sp., was isolated from a maize field in Senekal, Free State Province of South Africa. Morphological and molecular studies indicated the distinctness of S. biddulphi n. sp. from other Steinernema species. Steinernema biddulphi n. sp. is characterized IJs with average body length of 663 mm (606-778 µm), lateral fields with six ridges in mid-body region forming the formula 2,6,2. Excretory pore located anterior to mid-pharynx (D% = 46). Hyaline layer occupies approximately half of tail length.Male spicules slightly to moderately curved, with a sharp tip and golden brown in color. The first generation of males lacking a mucron on the tail tip while the second generation males with a short filamentous mucron. Genital papillae with 11 pairs and one unpaired preanal papilla. The new species is further characterized by sequences of the internal transcribed spacer (ITS) and partial 28S regions (D2-D3) of the ribosomal DNA (rDNA). Phylogenetic data show that S. biddulphi n. sp. belongs to the "bicornutum" clade within the Steinernematidae family. [ABSTRACT FROM AUTHOR]

Low-cost mass production of entomopathogenic nematodes (EPNs) is an important prerequisite towards their successful commercialisation. This study evaluated six low-cost solid substrate media forin vitromass production ofSteinernema innovationi. Cost analysis was undertaken and an estimated retail price was calculated. This was then compared to the costs of commercial EPN products currently on the market. The highest yield of infective juveniles (IJs) was obtained from a medium containing a puree of house fly,Musca domestica, larvae + 0.15 g canola oil, (781,678 ± 221 IJs/5 g medium). This medium also had the lowest number of adults remaining in the medium and dead IJs (<10%) at the time of harvest (Day 28). The estimated retail price (R243.27 per 50 million IJs) forS. innovationiproduced with our solid culture system was considerably lower than the market price for otherSteinernemaspecies products sold by E∼nema, BASF corporation, Koppert, BioBest and Natural Insect Control. The production system developed in this study offers a competitive technology to produce EPN products without having to invest in large-scale liquid fermentation equipment, by using a relatively cheap production medium and simple solid culture growing conditions using Erlenmeyer flasks. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematode species differ in their optimum storage temperature; therefore, we conducted a study on the survival and infectivity of the recently described Steinernema innovationi from South Africa at five storage temperatures (5°C, 10°C, 15°C, 20°C, and 25°C) over 84 d using 20,000 infective juveniles (IJ) in 25 ml aqueous suspension containing 0.1% formalin. Our results showed that survival was highest and most stable at 15°C, ranging from 84% to 88% after 84 d. Infectivity of IJ against Galleria mellonella larvae was >90% for all temperatures except for 5°C at which survival decreased to 10% after 84 d. In addition, we stored 2.5 million IJ on a sponge formulation in 15 ml of 0.1% formalin solution for 84 d at the optimum 15°C followed by 2 wk storage at 25°C. Storage of the IJ on a sponge formulation for 14 d at 25°C post 15°C storage for 84 d did not have a detrimental effect on IJ survival (87%) or infectivity to G. mellonella (95%). [ABSTRACT FROM AUTHOR]

Conidia of Beauveria bassiana and Metarhizium spp. smeared on glass slides were assayed for their responses to irradiation with weighted 312-nm UV-B and 365-nm UV-A at gradient doses of 0.005–1.1 and 1.0–18.0 J cm−2, respectively. All inverted, sigmoid dose–survival trends showed good fit to a survival model ( r2 ≥ 0.97), yielding respective UV-B LD50s of 0.23–0.59 and 0.05–0.65 J cm−2 for 24 B. bassiana and 36 Metarhizium isolates, and UV-A LD50s of 2.78–10.46 J cm−2 for 24 Metarhizium isolates. Myzus persicae apterae on detached leaves were sprayed with a concentrated spore suspension of B. bassiana or M. anisopliae, followed by exposure to the UV-B doses to cause 10–90% viability losses. These doses caused aphid mortality reductions as expected but affected neither spray-to-death period nor fungal growth on cadavers. The results highlight the merits of using UV-tolerant candidates and photoprotection measures in fungal formulations for pest control. [ABSTRACT FROM AUTHOR]

Abstract Leaf rust caused by Puccinia triticina is an important disease of wheat worldwide. Different experiments were conducted to determine efficacy of redworm and its extracts against leaf rust on wheat seedlings. The first experiment involved the use of vermicast and artificial soil as planting substrates, and living worms were introduced into soil for four months. This significantly influenced leaf rust severity, with the lowest severity recorded among inoculated plants grown in vermicast (12% severity), followed by soil pulverised with 30 worms (30%) and 20 worms (40%), while control had the highest rust severity (>70%). Second experiment watered the inoculated seedlings with the extracts (vermicast and vermiwash) which resulted into significant lower leaf rust severity of 35% and 53%, respectively while untreated plants had >85% disease severity. Vermicast, which had the highest leaf rust suppression, was further tested, whereby it reduced leaf rust infection up to 30% with increase in seedling shoot and root growth of 21% and 17%, respectively. Redworm enhances resistance to leaf rust infection on inoculated plant via increase in growth that suppresses rust development. [ABSTRACT FROM AUTHOR]