Olive anthracnose (OA), caused by fungal species belonging to Colletotrichum genus, is one of the major aerial olive diseases worldwide. Increasing restrictions on synthetic fungicides have intensified the search for sustainable alternatives based on biological control agents (BCAs). In this study, six BCAs (Aureobasidium pullulans PV-1033, Bacillus velezensis PV-700, Epicoccum nigrum RD4C, Phoma glomerata PV-375, Trichoderma asperellum IMI393899, and T. atroviride TS) were evaluated against 16 isolates representing six Colletotrichum species associated with OA in Spain and Italy. Antagonistic activity was assessed through dual-culture and volatile organic compounds (VOCs) in vitro assays, followed by efficacy tests on detached olive fruits and in planta. Bacillus subtilis QST 713 (Serenade® ASO) and copper sulphate were included as reference products. All BCAs significantly inhibited mycelial growth in vitro, although their efficacy varied with the Colletotrichum species and BCA tested. The two Trichoderma isolates consistently showed the strongest activity, particularly through VOCs production. In detached-fruit assays, disease suppression was pathogen-dependent; and P. glomerata PV-375 and T. atroviride TS were selected for further in planta evaluation against C. acutatum C9D2C and C. godetiae Col-511. Both BCAs significantly reduced disease incidence and disease progress in planta, providing levels of protection comparable to those achieved with B. subtilis QST 713 and copper sulphate. These findings demonstrate that BCA efficacy against OA depends on both pathogen species and experimental system, and highlight the importance of integrating in vitro, detached fruit, and in planta assays to identify promising BCAs for sustainable disease management.
Tobacco root rot is mainly a soil-borne disease caused by fungi such as Fusarium oxysporum, and it reduces both yield and quality. Traditional chemical control is effective but often leaves residues, whereas biological control, although environmentally safe, still suffers from poor colonization of beneficial microbes in the rhizosphere and unstable control efficacy in the field. Plant root exudate metabolites are recognized as crucial mediators that enhance the colonization of beneficial microorganisms. Despite this recognized importance, a deeper understanding of how metabolome-driven colonization of probiotics specifically determines plant resistance against soil-borne diseases is still lacking. Here, we first isolated, screened, and identified a probiotic strain, Bacillus subtilis HJ1-29, with antagonistic activity against the pathogenic fungus Fusarium sp . We then screened the root exudates for prebiotics that improve the colonization of HJ1-29 and identified leucine. We further examined the underlying mechanisms and found that leucine improved the chemotaxis and biofilm formation of HJ1-29, and the combination of HJ1-29 and leucine reduced spore production and altered the mycelial morphology of the fungal pathogen. Finally, pot experiments showed that the leucine-HJ1-29 treatment had the lowest disease index among all treatments, with a control efficacy of 97.8%, and increased the activities of PAL and POD in tobacco leaves. Overall, our results suggest that root-secreted leucine is associated with the recruitment of probiotic B. subtilis HJ1-29 and contributes to the suppression of the pathogen and to the control of Fusarium root rot. This study provides new insights into the use of functional synbiotics as a promising strategy for manipulating plant-microbiome interactions in sustainable agriculture.
Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) is a major pest of soybean, causing stay-green syndrome and significant losses in yield and quality. Though several parasitoids have been reported, their biological control potential is still limited due to low female progeny ratios and difficulties in mass rearing. To identify a parasitoid with high parasitism efficiency and strong mass production potential, we tested two brachypterous species of Anastatus (Hymenoptera: Eupelmidae) ( A. gastropachae and A. meilingensis ), and two strains of the species A. meilingensis ( A. meilingensis -1 and A. meilingensis -2) for host age preference and performance on R. pedestris eggs of different ages (0-, 2-, 4-, and 6-day-old). All three parasitoids ( A. gastropachae , A. meilingensis -1 and A. meilingensis -2) successfully parasitized host eggs across all age classes, with emergence rates exceeding 85% and minimal host-feeding activity. Parasitism rates were highest on 0-, 2-, and 4-day-old eggs. Among the tested parasitoids, A. meilingensis -2 consistently showed the highest parasitism levels and maintained a female progeny ratio above 60% on 2- and 4-day-old eggs, whereas the female ratio was below 10% for A. meilingensis -1 and zero for A. gastropachae . Moreover, individuals of A. meilingensis -2 emerging from R. pedestris eggs (i.e., F 1 generation) retained the ability to parasitize both 0-day-old and 4-day-old R. pedestris eggs, producing a female ratio exceeding 65% on both host ages. These results suggest that A. meilingensis -2 could be a potential biological control agent for the sustainable management of R. pedestris due to its high parasitism efficiency and favorable sex ratio.
Temperature fluctuations within high tunnel cropping systems can significantly influence the performance of parasitoid wasps used in biological control programs. We investigated the residual effects of short-term exposure to four realistic elevated temperature scenarios, previously measured in commercial berry tunnels in southwestern Germany, on two candidate parasitoids of spotted wing drosophila Drosophila suzukii (Diptera: Drosophilidae), Trichopria drosophilae (Hymenoptera: Diapriidae) and Pachycrepoideus vindemiae (Hymenoptera: Pteromalidae). Our results show that T. drosophilae was highly sensitive to overall short-term temperature increases, with significantly reduced adult survival probability after two days at maximum daily temperatures above 30 °C, and complete mortality above 34 °C. For T. drosophilae , all elevated temperature scenarios further reduced parasitism rates, offspring emergence and sex ratio, suggesting limited persistence and efficacy under thermal stress. In contrast, P. vindemiae displayed greater robustness: adult survival was stable or even increased under moderate overall short-term temperature increases, and offspring emergence and sex ratio remained unaffected across scenarios, though parasitism success declined at the highest temperature scenario. Given that high tunnels can accumulate heat beyond open-field conditions, our results therefore indicate that P. vindemiae is a more reliable candidate for use in such systems, while deployment of T. drosophilae may require additional mitigation strategies such as shading, ventilation, or repeated releases. Our findings emphasize the importance of considering thermal tolerance when selecting parasitoid species for integrated pest management programs in particular in protected cultivation systems.
The tribe Stethorini (Coleoptera: Coccinellidae), commonly called spider mite destroyers, comprises specialized mite predators with significant potential for biological control against phytophagous mites. This review synthesizes major advances following Chazeau (1985) and Biddinger et al. (2009), integrating recent findings in taxonomy, trophic ecology, and life-history biology, and field implementation. Key advances include revised global diversity (91 Stethorus and 16 Parastethorus species), elucidation of host plant‑mediated prey quality effects, and documentation of thermal conservatism in development alongside wide reproductive variation. Field implementations have demonstrated remarkable efficacy, complete Panonychus citri suppression in Chinese citrus through conservation, and 40–91% Tetranychus urticae reduction in Oregon hops using synthetic herbivore‑induced volatiles. Despite these successes, critical gaps constrain broader adoption: mass‑rearing costs remain prohibitive, pesticide compatibility is inferior to that of phytoseiid mites, and the impacts of climate change and alternative prey on predator performance remain unresolved. Practically, Stethorini are best deployed via conservation biocontrol in open‑field systems where resident populations naturally establish, rather than costly augmentative releases. Looking forward, we outline a three-priority research roadmap, deciphering the genomic basis of mite specialization, engineering cost-effective artificial diets, and developing predictive frameworks for climate-smart deployment, that could transform these underutilized predators into more reliable and economically viable components of sustainable mite management, reducing acaricide dependence worldwide.
