title: Developing and optimising the effectiveness of entomopathogenic fungi for biological control of Cydia pomonella: A multifaceted approach
Creators: name: Antara, Nushrat Harun
Publisher: name: UNSPECIFIED
Year: 2024

description: The food industry, a cornerstone of global health and economy, faces many challenges in meeting the ever-increasing demand for nutritious and accessible products. Central to the success of this industry is the agricultural sector, particularly the cultivation of crops such as pome fruits, which are essential for diversifying diets and providing essential nutrients. However, the journey from farm to fork is not straightforward, with the limited availability of arable land and the relentless threat of insects, microbial pathogens, and pests such as the codling moth. The codling moth (Cydia pomonella, Lepidoptera: Tortricidae) is a major threat to pome fruit production, causing considerable losses to fruit farmers not only in Europe but globally. In response to the drawbacks of synthetic insecticides, many farmers are turning to biocontrol strategies, including the use of entomopathogenic fungi (EPF), as sustainable alternatives for pest management. Consequently, research efforts focused on the screening and application of EPF have increased significantly in recent years, reflecting the growing interest in environmentally friendly pest management practices worldwide. This work, which involved the isolation of 32 EPF strains from soil samples using the insect bait method and one strain from strain collection of Julius Kühn Institute (JKI), aimed not only to assess the occurrence and prevalence of these fungi, but also to investigate their virulence and the key role of chitinase production in enhancing their effectiveness to control the pest insect. Following identification procedures by microscopic examination and molecular sequencing of the ITS region, the initial screening phase focused on assessing the virulence of these strains, setting a high benchmark of over 80 % mortality against C. pomonella. This rigorous selection criterion led to the identification of 13 strains, with promising virulence. Among these, four strains i.e. JKI-BI-1496 (Cordyceps fumosorosea), two strains of JKI-BI-2620 (Beauveria bassiana), JKI-BI-2642 (Beauveria bassiana), and JKI-BI-2647 (Metarhizium robertsii), stood out for their higher chitinase activity, a crucial enzyme that facilitates the degradation of chitin, a key component of the insect exoskeleton, thereby enhancing the fungal invasion and infection process. The research also investigated the environmental adaptability of these strains, subjecting them to a range of temperature conditions and simulated sunlight exposure to assess their resilience and effectiveness under different environmental stressors. This phase was critical in determining the potential field applicability of the selected EPF strains, given the diverse and often challenging conditions found in natural agricultural environments. The study also investigated the growth and virulence potential of these fungi in four different media types — malt peptone, malt peptone with 1 % chitin, potato dextrose, and potato dextrose with 1 % chitin — to determine the optimal conditions for their proliferation and virulence. The aim of this approach was to enhance the production potential of the strains, with a particular focus on the use of chitin-amended media to simulate the natural infection process and thereby improve the efficacy of the fungi against C. pomonella. Particular attention was paid to C. fumosorosea, which showed promising properties in preliminary tests. One of the most significant findings of the study was the marked improvement in fungal virulence and effectiveness when grown in a medium containing 1 % colloidal chitin (CC), which not only facilitated a higher mortality in bioassays against C. pomonella larvae but also influenced various growth parameters, including spore and biomass production, germination and higher stability as freeze-dried spores. However, the addition of 1 % CC also presented challenges. It notably affected the fungi's resilience to prolonged sunlight exposure, which is a critical factor to consider for the field application of these biocontrol agents. To address the limitations posed by sunlight sensitivity, the research explored the effectiveness of nine water-soluble sunlight protectants. Black tea was identified as a particularly effective agent in preserving the viability and germination of submerged spores under simulated sunlight conditions. Additionally, spores coated with calcofluor white resulted higher shelf life than other additives. This approach to enhance the environmental stability of C. fumosorosea spores could be a promising strategy for the application of fungal biocontrol agents against C. pomonella in organic apple orchards. The findings emphasise the complex interplay between fungal virulence, environmental adaptability, and innovative formulation strategies in the development of effective biological control agents (BCAs). This research highlights the potential of chitin-amended media and sunlight protectants to enhance the effectiveness and stability of EPF. The findings offer valuable insights into the optimization of biocontrol strategies, paving the way for more sustainable and environmentally friendly pest management approaches in agriculture.