Abstract Microorganisms with beneficial traits for protection of plants against pest and diseases and for biostimulation of plants have been selected amongst the huge diversity of microorganisms naturally occurring in the environment. The use of microbial products has to be approved by governmental authorities before they can be applied in the EU. Frameworks of regulations have been developed with particular emphasis on risk assessments of the active substances and the formulated products. Distinctly different regulations are currently used for microbial plant protection products and microbial biostimulants. If the intended purpose of use results in different potential risks, a separation into different legal frameworks is adequate. This may be the case if distinct microbial groups used for different purposes differ in toxicity and pathogenicity. A separation may also be adequate if methods and rates of application or targeted environmental compartments differ resulting in different expected risks for humans, animals, plants or the environment. Also the exploitation of different modes of action may result in different levels of risks and urge different ways of risks assessments. Objective of this review is to stimulate discussion on the reasoning of the separated regulatory frameworks and contrasting risk assessments currently applied in the EU for beneficial microorganisms used for plant protection and used for biostimulation of plants.

Several stink bugs species constitute an important pest complex in soybean worldwide. Tachinidae parasitoids are an important tool to be exploited in conservation biological control programs. We evaluated parasitism of pentatomids in different periods of their life-history: diapause (late autumn and winter), start of activity (spring) and full activity (late summer and early autumn). During the growing seasons 2017-2018 and 2019-2020, we collected stink bugs from soybean, alfalfa and wheat crops and natural vegetation, of three species (Nezara viridula, Edessa

Thousand cankers disease of Juglans (walnut) and Pterocarya (wingnut) spp. (Fagales: Juglandaceae) is caused by the fungal pathogen Geosmithia morbida Kolarík, Freeland, Utley, and Tisserat (Hypocreales: Bionectriaceae) and bark beetle pest/vector, Pityophthorus juglandis Blackman (Coleoptera: Curculionidae). To further the development of biological management strategies for thousand cankers disease, we assessed the ability of 14 endophytic Trichoderma (Hypocreales: Hypocreaceae) isolates and the commercially available isolate T. afroharzianum strain KRL-AG2 to inhibit the in vitro growth of three different G. morbida isolates via mycoparasitism and antibiosis. To identify factors that may affect field success of candidate biological control agents, we quantified the growth responses of Trichoderma spp. and the commercially available entomopathogenic fungus, Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Cordycipitaceae) strain GHA, to the plant secondary metabolite and antimicrobial compound, juglone in vitro. A total of 12 Trichoderma isolates (from six different Trichoderma species) demonstrated antagonistic activity towards G. morbida in dual-plate assays. Juglone consistently reduced the growth of B. bassiana strain GHA and 14 of the 15 screened Trichoderma isolates in vitro. Additionally, one metabolite-producing Trichoderma isolate, TN4-47, completely inhibited the growth of all three G. morbida isolates across all tested metabolite concentrations and had comparatively greater tolerance to juglone compared to other Trichoderma isolates. Future lines of research should focus on characterizing the active antagonistic compound present in the metabolite filtrates, determine the mode of action of the active component(s), and elucidate how abiotic and biotic factors may influence the growth, persistence, and antagonistic activity of candidate biological control agents in planta.

Prickly acacia (Vachellia nilotica subsp. indica (Benth.) Kyal. & Boatwr.; Fabales: Fabaceae) is a Weed of National Significance and a target for biological control in Australia. Currently there are no effective biological control agents for the weed in Australia. Based on genetic and climate matching, a gall thrips (Acaciothrips ebneri Karny; Thysanoptera: Phlaeothripidae) inducing rosette galls resulting in shoot tip dieback, was identified as a prospective biological control agent from Ethiopia. No-choice host-specificity tests were conducted on 59 test plant species in a high security quarantine in Brisbane, Australia. Acaciothrips ebneri is host-specific, inducing galls and reproducing only on prickly acacia. Acaciothrips ebneri, as predicted by the CLIMEX model, is suited to hot and arid western Queensland where major prickly acacia infestations occur. The Australian Government approved A. ebneri for field release in October 2022. This is the first time a true gall-inducing thrips has ever been approved as a weed biological control agent. Field releases commenced in January 2023 and are in progress. There are early signs of field establishment resulting in shoot tip die back in the field, and field release and monitoring will continue.