Some entomopathogenic fungi such as Metarhizium and Beauveria not only have the ability to infect and kill insects but also the capability to associate with plant roots. The potential benefits from this plant-fungus association include nutrient acquisition, plant growth promotion and protection against stressors. The objective of this study was to evaluate the delivery of entomopathogenic fungi in seed coating to determine whether the fungal presence affected maize performance. Additionally, fungal biocontrol ability was assessed in terms of plant resistance to the larvae of Costelytra giveni (Coleoptera: Scarabaeidae) and to the fungus Fusarium graminearum (Nectriaceae). Maize seeds were coated with conidia from Metarhizium spp. or Beauveria bassiana and plant performance was evaluated as seed germination and plant dry weight. Larval mortality and the presence of Fusarium root rot symptoms were also determined. The entomopathogenic fungal persistence on the maize rhizosphere was demonstrated with a M. anisopliae isolate expressing the green fluorescent protein. Presence of both challengers was detrimental to maize performance with 33% reduction in root dry weight in control plants while no variation was observed when the entomopathogenic fungi were used to coat seeds. Some seed coatings resulted in up to 67% mycosis of C. giveni larvae and a reduction in Fusarium rot root symptoms between 24–44%. This study showed that seed coating with conidia of Metarhizium or Beauveria can be used as a delivery system for pests and plant pathogen control, while at the same time hyphae formed a close association with plant roots after conidial germination.

The nonspore-forming bacterium Serratia entomophila may be used to control the New Zealand grass grub (Costelytra giveni) but is sensitive to environmental stress and must be formulated to improve survival. Existing formulations require subsurface application limiting the area that can be treated. Formulations that allow delivery by broadcast methods are desirable to reduce application costs and increase the potential for aerial application to inaccessible areas. Two formulations were prepared for use in experiments examining the persistence and movement of inoculum through soil. When granules were applied to the soil surface, bacterial survival was negligible in uncoated core, but improved with increasing thickness of the coating. Both survival of bacteria and release into the soil were influenced by soil moisture content. Granules at <12% soil moisture showed high bacterial mortality and reduced delivery to the soil, while at 28% soil moisture most bacteria were released to the soil. There was a high level of survival of the applied bacteria within granules at 20% and 28% soil moisture. The formulations maintained viability of S. entomophila in granules stored under ambient conditions for more than 6 months. In laboratory and field tests, the application of granules caused disease in the target grass grub larvae, whether application was applied to the surface or subsurface. In field trials, broadcast applied granules could produce equivalent disease to thin-coat granules drilled into the soil, but these levels of disease were associated with the occurrence of precipitation shortly after application.