Optimization of application techniques and dosages of Heterorhabditis bacteriophora for biologically controlling the larvae of the western corn rootworm

Optimierung von Ausbringungstechnik und Konzentration von Heterorhabditis bacteriophora zur Bekämpfung der Larven des Westlichen Maiswurzelbohrer

Field survival analysis of adult Diabrotica virgifera virgifera

Analyse der Überlebensrate von Diabrotica virgifera virgifera im Fel

How maize root volatiles affect the efficacy of entomopathogenic nematodes in controlling the western corn rootworm?

Because the ferocious maize pest Diabrotica virgifera virgifera LeConte can adapt to all currently used control strategies, focus has turned to the development of novel, more sustainable control methods, such as biological control using entomopathogenic nematodes (EPN). A good understanding of the biology and behaviour of these potential control agents is essential for their successful deployment. Root systems of many maize varieties emit (E)-β-caryophyllene (EβC) in response to feeding by larvae of the beetle D. v. virgifera. This sesquiterpene has been shown to attract certain species of EPN, thereby enhancing their control potential. In this study, we tested the effect of this root-produced volatile on the field efficacy of the three EPN Heterorhabditis bacteriophora, Heterorhabditis megidis and Steinernema feltiae against D. v. virgifera larvae in southern Hungary. By comparing beetle emergence and root damage for two maize varieties, one that emits EβC and one that does not, it was found that root protection by H. megidis and S. feltiae was higher on the emitting variety, but this was not the case for H. bacteriophora. Overall, all three nematode species showed good control potential. We conclude that, if properly applied and in combination with the right maize variety, the release of these nematodes can be as effective as other control method

Oviposition preferences of Diabrotica virgifera virgifera: Multiple-choice field cage trials

Eiablagepräferenzen von Diabrotica virgifera virgifera: Multiple-choice-Käfigversuche im Fel

Dispersal and oviposition behaviour of Diabrotica virgifera virgifera in non-maize crops to improve advice and guidelines for crop rotation

Verbreitungs- und Eiablageverhalten von Diabrotica virgifera virgifera in Nicht-Mais-Kulturen zur Verbesserung von Beratung und Richtlinien für den Fruchtwechse

Differences between independently invading and crossed populations of the alien maize pest Diabrotica virgifera virgifera

Unterschiede zwischen unabhängig einwandernden und gekreuzten Populationen des neuen Maisschädlings Diabrotica virgifera virgifer

Coming to stay or to go?: Stay intention and involved uncertainty of international students

Countries compete for young talents to alleviate skilled‐labor shortage. International students, who stay after graduation, allow host countries to overcome this challenge. This study investigates the factors associated with international students' intention to stay or to go after graduation from a host country's perspective. In contrast to the literature, this analysis employs survey data collected from first‐semester students. This assures that the analysis is not distorted by attrition. Furthermore, it allows policymakers to address those students who would be no longer around later in the absence of any policy measure. At the same time, it requires to deal with uncertainty as the actual migration decision will be later. This study introduces a set of uncertainty models to the migration context. The results show that, next to career opportunities and a stay in the host country before the studies, being enrolled in a Bachelor program instead of a Master program is significantly associated with the intention to stay. The findings are largely robust to different approaches accounting for the uncertainty involved. Further, Master students are found to be significantly more uncertain than Bachelor students

Influence of soil on the efficacy of entomopathogenic nematodes in reducing Diabrotica virgifera virgifera in maize

The use of entomopathogenic nematodes is one potential non-chemical approach to control the larvae of the invasive western corn rootworm (Diabrotica virgifera virgifera LeConte, Coleoptera: Chrysomelidae) in Europe. This study investigated the efficacy of Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae), Heterorhabditis megidis Poinar, Jackson and Klein (Rh., Heterorhabditidae) and Steinernema feltiae Filipjev (Rh., Steinernematidae) in reducing D. v. virgifera as a function of soil characteristics. A field experiment was repeated four times in southern Hungary using artificially infested maize plants potted into three different soils. Sleeve gauze cages were used to assess the number of emerging adult D. v. virgifera from the treatments and untreated controls. Results indicate that nematodes have the potential to reduce D. v. virgifera larvae in most soils; however, their efficacy can be higher in maize fields with heavy clay or silty clay soils than in sandy soils, which is in contrast to the common assumption that nematodes perform better in sandy soils than in heavy soils

Secondary contact and admixture between independently invading populations of the Western corn rootworm, diabrotica virgifera virgifera in Europe

The western corn rootworm, Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae), is one of the most destructive pests of corn in North America and is currently invading Europe. The two major invasive outbreaks of rootworm in Europe have occurred, in North-West Italy and in Central and South-Eastern Europe. These two outbreaks originated from independent introductions from North America. Secondary contact probably occurred in North Italy between these two outbreaks, in 2008. We used 13 microsatellite markers to conduct a population genetics study, to demonstrate that this geographic contact resulted in a zone of admixture in the Italian region of Veneto. We show that i) genetic variation is greater in the contact zone than in the parental outbreaks; ii) several signs of admixture were detected in some Venetian samples, in a Bayesian analysis of the population structure and in an approximate Bayesian computation analysis of historical scenarios and, finally, iii) allelic frequency clines were observed at microsatellite loci. The contact between the invasive outbreaks in North-West Italy and Central and South-Eastern Europe resulted in a zone of admixture, with particular characteristics. The evolutionary implications of the existence of a zone of admixture in Northern Italy and their possible impact on the invasion success of the western corn rootworm are discussed