A study to detect the diversity of endophytic Actinobacteria from Australian rice was conducted using culture-dependent and culture-independent methods. Rice samples were collected from the rice growing area near Yanco, New South Wales, Australia. Isolation of the endophytic Actinobacteria was done over two consecutive growing seasons. The results demonstrated that most isolates were obtained from plants 10 weeks and older, and only a few were found in younger plants. Microbispora spp. were the most commonly isolated endophytic Actinobacteria (94%) with Streptomyces spp. and other genera present at lower numbers (6%). The culture-dependent method findings were confirmed by T-RFLP profile analysis. Restriction digests using HhaI and RsaI also showed an abundance of terminal restriction fragments (TRFs) profiles related to the genus Microbispora. Furthermore, other biological properties of the endophytic Actinobacteria isolates were also determined. Four isolates, Saccharothrix OSH21, Saccharopolyspora OSR26, Streptomyces OSR46 and Microbispora OSR61, were found to suppress the growth of the pathogenic fungus Rhizoctonia solani. Moreover, these isolates might be able to promote plant growth by producing indole acetic acid or to solubilise phosphate making this nutrient available for plant uptake.

There are increasing efforts aiming to utilise endophytes as biological control agents (BCAs) to improve crop production. However, reliability remains a major practical constraint for the development of novel BCAs. Many organisms are adapted to their specific habitat; it is optimistic to expect that a new organism added can find a niche or even out-compete those adapted and already present. Our approach for isolating novel BCAs for specific plant diseases is therefore to look in healthy plants in a habitat where disease is a problem, since we predict that it is more likely to find competitive strains among those present and adapted. In vitro inhibitory activities often do not correlate with in planta efficacy, especially since endophytes rely on intimate plant contact. They can, however, be useful to indicate modes of action. We therefore screen for in planta biological activity as early as possible in the process in order to minimise the risk of discarding valuable strains. Finally, some fungi are endophytic in one situation and pathogenic in another (the mutualism–parasitism continuum). This depends on their biology, environmental conditions, the formulation of inoculum, the health, developmental stage and cultivar of the host plant, and the structure of the plant microbiome.

In recent years, research into novel plant protection strategies with endophytic entomopathogenic fungi has increased markedly. However, current applications of these fungi are mostly not supported by targeted formulation strategies which should enhance fungal establishment in close proximity to plant tissue and promote endophytism. Further drawbacks are low stability of fungal propagules during drying and storage, difficult handling as well as high dosages and costs per hectare. Formulation has the potential to substantially improve all of these characteristics to come closer to implementation of these fungi in integrated pest management. This chapter reviews the currently available literature on application of formulated endophytic entomopathogenic fungi via sprays, seed treatments, and sowing of granules and beads. It further addresses future trends in formulation science to overcome current challenges of endophytic entomopathogenic fungi regarding consistent efficacy particularly under field conditions.