Effect of Norwegian entomopathogenic fungal isolates against <em>Otiorhynchus sulcatus </em>larvae at low temperatures and persistence in strawberry rhizospheres

AbstractBiological control of belowground stages of the black vine weevil Otiorhynchus sulcatus F. (Coleoptera: Curculionidae) in strawberries in cool temperate regions using entomopathogens is challenged by low temperatures during the periods when larvae are vulnerable to infections. In a laboratory study we tested six indigenous Norwegian isolates of entomopathogenic fungi (one Beauveria bassiana, three Beauveria pseudobassiana, and two Metarhizium brunneum; Ascomycota: Hypocreales) for their efficacy against O. sulcatus larvae at 6, 12, and 18°C. At the lowest temperature only Beauveria spp. affected survival of O. sulcatus while all three fungal species reduced larval survival compared to the control treatment at 12 and 18°C. Two of the Norwegian isolates, one B. pseudobassiana and one M. brunneum, were then evaluated for long-term persistence (>1year) in the bulk soil and the rhizosphere soil of strawberries in a semi-field experiment. An exotic isolate of M. brunneum sharing origin with a widespread commercial biocontrol agent (F52/Met52 (Novozymes)) was included for comparison. All three isolates showed significantly higher abundances in the rhizosphere soil compared to bulk soil at 153, 366, and 471days after inoculation, thus indicating rhizosphere competence for B. pseudobassiana. Notably, CFU levels for both Norwegian isolates were much higher than for the exotic M. brunneum isolate. Selection of locally adapted isolates may therefore be of importance when considering biocontrol strategies of belowground pests in strawberry production

Distribution and Prolonged Diapause of the Rowan Seed Predators Argyresthia conjugella (Lepidoptera: Yponomeutidae) and Megastigmus brevicaudis (Hymenoptera: Torymidae) and their Parasitoids in Norway

The seed predator Argyresthia conjugella Zeller has rowan as its preferred host plant. In years of poor fruiting in rowan, it oviposits on apples. To improve the knowledge of this apple pest, rowanberries were collected from localities all over Norway from 1971 to 1985, and seed predators and their parasitoids were allowed to emerge for up to five years. Two species of seed predators, A. conjugella and Megastimus brevicaudis Ratzeburg, and seven species of parasitic Hymenoptera were common. The distribution of these species is shown on EIS (European Invertebrate Survey) maps of Norway. The biology of the parasitoids is summarized based on the published literature and their behavior during emergence. The tendency for delayed emergence, which is an indication of prolonged diapause, was more pronounced in M. brevicaudis than in A. conjugella, the former appearing in all five years. Five of the parasitoids also delayed their emergence, and three of them to a high degree, up to five years. Prolonged diapause must be taken into account in studies of rowanberry insect guilds.publishedVersio

Confirmation of Neozygites floridana azygospore formation in two-spotted spider mite (Tetranychus urticae) in strains from tropical and temperate regions

AbstractNeozygites floridana is an obligate fungal pathogen of mites in the family Tetranychidae and is an important natural enemy of the two-spotted spider mite (Tetranychus urticae). Until now, information about the formation of azygospores remained to be fully confirmed. In this study, we document the formation of azygospores by a Brazilian N. floridana strain and the formation of azygospores and zygospores by a Norwegian N. floridana strain, both in the host T. urticae. Evidence of both zygosporogenesis and azygosporogenesis was also found in the same individual in the Norwegian stains. Further we report the presence of immature azygospores with 1–3 nuclei for the Norwegian strains, immature resting spores (probably azygospores) with 1–8 nuclei for the Brazilian strain, and mature resting spores with 2 nuclei for both the Norwegian and the Brazilian strains (azygo- or zygospores). Our observations suggest that the immature resting spore (prespore) of both strains begins in a multinucleate condition but that the nuclear number is reduced during maturation until mature resting spore is binucleate regardless of its origin as a zygospore or azygospore

Biologisk veiledningsprøving 2022. Skadedyrmidler

I 2022 ble det utført forsøk med skadedyrmidler i frukt og bær, og anlagt et forsøk i hodekål. I eple er det utført forsøk med ulike kjemiske og biologiske plantevernmidler mot blodlus (Eriosoma lanigerum), rognebærmøll (Argyresthia conjugella) og andre sommerfuglarter. I søtkirsebær er det utført et forsøk med feller med gjærlukt kombinert med farge for å øke fangsten og eventuelt også bekjempelse av kirsebærflue (Rhagoletis cerasi). Det er også utført forsøk med alternative midler mot bringebærbarkgallmygg (Resseliella theobaldi) i økologisk bringebær. Forsøket mot kålmøll i hodekål ble anlagt og delvis registrert, men ikke fullført på grunn av svakt angrep. Forsøkene og enkelte forsøksledd er finansiert av ulike prosjekter og finansieringskilder.Biologisk veiledningsprøving 2022. SkadedyrmidlerpublishedVersionpublishedVersio

Biologisk veiledningsprøving 2022. Skadedyrmidler

I 2022 ble det utført forsøk med skadedyrmidler i frukt og bær, og anlagt et forsøk i hodekål. I eple er det utført forsøk med ulike kjemiske og biologiske plantevernmidler mot blodlus (Eriosoma lanigerum), rognebærmøll (Argyresthia conjugella) og andre sommerfuglarter. I søtkirsebær er det utført et forsøk med feller med gjærlukt kombinert med farge for å øke fangsten og eventuelt også bekjempelse av kirsebærflue (Rhagoletis cerasi). Det er også utført forsøk med alternative midler mot bringebærbarkgallmygg (Resseliella theobaldi) i økologisk bringebær. Forsøket mot kålmøll i hodekål ble anlagt og delvis registrert, men ikke fullført på grunn av svakt angrep. Forsøkene og enkelte forsøksledd er finansiert av ulike prosjekter og finansieringskilder.Biologisk veiledningsprøving 2022. SkadedyrmidlerpublishedVersio

Biologisk veiledningsprøving 2021. Sopp- og skadedyrmidler

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Abiotic and Biotic Factors Affecting Resting Spore Formation in the Mite Pathogen Neozygites floridana

Neozygites floridana is an obligate mite pathogenic fungus in the Entomophthoromycota. It has been suggested that resting spores of this fungus are produced as a strategy to survive adverse conditions. In the present study, possible mechanisms involved in the regulation of resting spore formation were investigated in the hosts Tetranychus urticae and Tetranychus evansi. Abiotic and biotic factors mimicking conditions that we, based on earlier field studies, thought might induce resting spores in temperate and tropical regions were tested with isolates from Norway and Brazil. A total of 42 combinations of conditions were tested, but only one induced the formation of a high number of resting spores in only one isolate. The Brazilian isolate ESALQ1420 produced a large number of resting spores (51.5%) in T. urticae at a temperature of 11 ∘ C, photoperiod of 10L:14D, and light intensity of 42-46 ( mol m −2 s −1 ) on nonsenescent plants (nondiapausing females). Resting spores of the Brazilian N. floridana isolate ESALQ1421 were found at very low levels (up to 1.0%). Small percentages of T. urticae with resting spores (0-5.0%) were found for the Norwegian isolate NCRI271/04 under the conditions tested. The percentages of resting spores found for the Norwegian isolate in our laboratory studies are similar to the prevalence reported in earlier field studies

Computer-assisted image processing to detect spores from the fungus Pandora neoaphidis

This contribution demonstrates an example of experimental automatic image analysis to detect spores prepared on microscope slides derived from trapping. The application is to monitor aerial spore counts of the entomopathogenic fungus Pandora neoaphidis which may serve as a biological control agent for aphids. Automatic detection of such spores can therefore play a role in plant protection. The present approach for such detection is a modification of traditional manual microscopy of prepared slides, where autonomous image recording precedes computerised image analysis. The purpose of the present image analysis is to support human visual inspection of imagery data – not to replace it. The workflow has three components: • Preparation of slides for microscopy. • Image recording. • Computerised image processing where the initial part is, as usual, segmentation depending on the actual data product. Then comes identification of blobs, calculation of principal axes of blobs, symmetry operations and projection on a three parameter egg shape space.publishedVersio

Effect of three isolates of Pandora neoaphidis from a single population of Sitobion avenae on mortality, speed of kill and fecundity of S. avenae and Rhopalosiphum padi at different temperatures

We studied the effect of three Pandora neoaphidis isolates from one Sitobion avenae population, three temperatures, and two aphid species namely S. avenae and Rhopalosiphum padi on (i) aphid mortality, (ii) time needed to kill aphids, and (iii) aphid average daily and lifetime fecundity. A total of 38% of S. avenae and 7% of R. padi died and supported fungus sporulation. S. avenae was killed 30% faster than R. padi. Average daily fecundity was negatively affected only in S. avenae inoculated with, but not killed by, P. neoaphidis. Nevertheless, lifetime fecundity of both aphid species inoculated and sporulating with P. neoaphidis was halved compared to lifetime fecundity of surviving aphids in the control. Increased temperature resulted in higher mortality rates but did not consistently affect lethal time or fecundity. Results suggest that (i) temperature effects on virulence differ between isolates, even when obtained within the same host population, and (ii) even though an isolate does not kill a host it may reduce its fecundity. Our findings are important for the understanding of P. neoaphidis epizootiology and for use in pest-natural enemy modelling.Effect of three isolates of Pandora neoaphidis from a single population of Sitobion avenae on mortality, speed of kill and fecundity of S. avenae and Rhopalosiphum padi at different temperaturespublishedVersio