Efficacy of biological control agents for the control of western corn rootworm

Abstract: The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, has beenintroduced to Europe more than 20 years ago, and it is a well-established maize pest in Hungarysince 1995. The larvae of WCR cause damage on the maize roots. The efficacy of variousbiological control agents (BCAs), such as fermented cultures of various entomopathogenic toxinproducing preparations of Bacillus thuringiensis, and some strains of the entomopathogenicconidial fungus Metarhizium anisopliae, was screened against the larvae of WCR but thepractical application of them still needs additional research and development inputs. In in vitrotests, WCR larvae were treated with microbial products (fermented cell cultures or sporesuspensions in various concentrations) at the second larval stage. Larvae were fed with freshlygerminated maize roots and larval mortality was recorded until pupation. In greenhouseexperiments maize plants were grown in pots placed in isolators. WCR eggs (20 for each plant)were put directly under the seeds. In greenhouse experiments the microbial preparations wereapplied at the time of sowing, in the same way as they were applied in the in vitro trials. Onemonth after the planting, the root mass was measured, and the damage caused by larvae wasdetermined based on the modified IOWA 1-6 scale. Most of the bacterial preparations and fungalstrains proved to be effective both in killing WCR larvae and preventing root damage on maizeplants. Some microbial treatments almost reached the efficacy of the control treatments(Tefluthrin (FORCE 1.5 G) and Bacillus thuringiensis var. tenebrionis (NOVODOR FC)) and canbe considered as promising control agents of WCR.