Development of an attract-and-kill co-formulation containing Saccharomyces cerevisiae and neem extract attractive towards wireworms.

Background: Wireworms (Coleoptera: Elateridae) are major insect pests of worldwide relevance. Owing to the progressive phasing-out of chemical insecticides, there is great demand for innovative control options. This study reports on the development of an attract-and-kill co-formulation based on Ca-alginate beads, which release CO and contain neem extract as a bioinsecticidal compound. The objectives of this study were to discover: (1) whether neem extract can be immobilized efficiently, (2) whether CO -releasing Saccharomyces cerevisiae and neem extract are suitable for co-encapsulation, and (3) whether co-encapsulated neem extract affects the attractiveness of CO -releasing beads towards wireworms.

Results: Neem extract was co-encapsulated together with S. cerevisiae, starch and amyloglucosidase with a high encapsulation efficiency of 98.6% (based on measurement of azadirachtin A as the main active ingredient). Even at enhanced concentrations, neem extract allowed growth of S. cerevisiae, and beads containing neem extract exhibited CO -emission comparable with beads without neem extract. When applied to the soil, the beads established a CO gradient of >15 cm. The co-formulation containing neem extract showed no repellent effects and was attractive for wireworms within the first 24 h after exposure.

Conclusion: Co-encapsulation of S. cerevisiae and neem extract is a promising approach for the development of attract-and-kill formulations for the control of wireworms. This study offers new options for the application of neem extracts in soil. © 2017 Society of Chemical Industry.