Phylogenetic evidence for the invasion of a commercialized European Phasmarhabditis hermaphrodita lineage into North America and New Zealand

Biological control (biocontrol) as a component of pest management strategies reduces reliance on synthetic chemicals, and seemingly offers a natural approach that minimizes environmental impact. However, introducing a new organism to new environments as a classical biocontrol agent can have broad and unanticipated biodiversity effects and conservation consequences. Nematodes are currently used in a variety of commercial biocontrol applications, including the use of Phasmarhabditis hermaphrodita as an agent targeting pest slug and snail species. This species was originally discovered in Germany, and is generally thought to have European origins. P. hermaphrodita is sold under the trade name Nemaslug®, and is available only in European markets. However, this nematode species was discovered in New Zealand and the western United States, though its specific origins remained unclear. In this study, we analyzed 45 nematode strains representing eight different Phasmarhabditis species, collected from nine countries around the world. A segment of nematode mitochondrial DNA (mtDNA) was sequenced and subjected to phylogenetic analyses. Our mtDNA phylogenies were overall consistent with previous analyses based on nuclear ribosomal RNA (rRNA) loci. The recently discovered P. hermaphrodita strains in New Zealand and the United States had mtDNA haplotypes nearly identical to that of Nemaslug®, and these were placed together in an intraspecific monophyletic clade with high support in maximum likelihood and Bayesian analyses. We also examined bacteria that co-cultured with the nematode strains isolated in Oregon, USA, by analyzing 16S rRNA sequences. Eight different bacterial genera were found to associate with these nematodes, though Moraxella osloensis, the bacteria species used in the Nemaslug® formulation, was not detected. This study provided evidence that nematodes deriving from the Nemaslug® biocontrol product have invaded countries where its use is prohibited by regulatory agencies and not commercially available

Thermotolerance of Fungal Conidia

Conidia of entomopathogenic fungi (EF) are the propagules most frequently used in arthropod biocontrol programs. This anamorphic form is essential for the infection process, including spore germination, penetration, vegetative growth, conidiogenesis and dissemination. Most EF are mesophilic and can develop between 10 and 40 °C, but optimal growth is between 25 and 35 °C. Abiotic factors, especially temperature (high or low) can determine their viability, virulence and success or failure of infection process. Temperature has the highest impact on conidial stress inhibiting metabolic processes, such as decreased morphogenesis during germination, protein denaturation and membrane disorganization. Several studies show that some strains of Beauveria spp., Metarhizium spp., and Isaria spp. exhibit conidial survival even when grown at high temperatures, indicating a relationship between conidial thermotolerance and their geographical isolation origin. Moreover, the high variability in fungal thermotolerance is also dependent of the culture media composition and growth condition. EF that grow at high temperatures do not grow at low temperatures and vice versa. Moreover, when growth conditions are not set at optimal temperatures, EF development is affected and their effectiveness in biological control programs of arthropods is reduced. Thermal stress directly impacts on fungal strains ability to target arthropods and their environmental activity performance. The screening for fungal strains with a higher thermotolerance and the improvement on conidial formulations may aid in optimizing the conditions for biocontrol agent application.Fil: Paixão, Flávia R. S.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner"; ArgentinaFil: Fernandes, Éverton. Universidade Federal de Goiás; BrasilFil: Pedrini, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner"; Argentin

Insects as chemosensors of humans and crops

Insects transmit disease to hundreds of millions of people a year, and cause enormous losses to the world's agricultural output. Many insects find the human or plant hosts on which they feed, and identify and locate their mates, primarily through olfaction and taste. Major advances have recently been made in understanding insect chemosensation at the molecular and cellular levels. These advances have provided new opportunities to control insects that cause massive damage to health and agriculture across the world