Conidia, enzymes and metabolites of Purpureocillium lilacinum Coad 4015 for the control of nematodes and insect pests: laboratory and field studies
Insect pests and plant-parasitic nematodes cause significant yield losses in agriculture, and the use of mycoparasitic fungi for their control has been increasing. However, a limited range of fungi has proven activity against these organisms, reinforcing the need to evaluate new strains and species with potential for biological control. This thesis aimed to characterize and evaluate the potential of a new strain of Purpureocillium lilacinum (COAD 4015) as a multi-target biological control agent, focusing on the management of nematodes and insect pests of agricultural importance. In Chapter 2, the strain was tested for the control of root-knot nematodes of the genus Meloidogyne in tomato crops. The application of conidia at different concentrations significantly reduced the number of eggs and juveniles in the soil and roots, in addition to promoting plant growth. The absence of fungal growth at 36°C indicated low risk to human health, reinforcing its safety for agricultural use. In Chapter 3, the efficacy of P. lilacinum was evaluated for the field control of the corn leafhopper (Dalbulus maidis). Two trials were conducted: one under commercial field conditions and another in a controlled experimental setting. The application of the fungus with an oil-based adjuvant improved conidial adhesion to the insect’s cuticle, overcoming natural barriers such as brochosomes, and resulted in population reduction of the pest, as well as a significant increase in maize grain yield. In Chapter 4, the pathogenicity of conidia, enzymes, and metabolites was investigated against D. maidis, Tenebrio molitor, and four lepidopteran pest species. The results indicated low overall pathogenicity, with moderate effects observed only in Rachiplusia nu (enzymes) and marginal response in Spodoptera frugiperda. Notably, the addition of P. lilacinum to the chemical insecticide acephate (active ingredient of the commercial product Acefato®) resulted in a 50% reduction in D. maidis mortality compared to acephate alone, suggesting a possible negative interaction between treatments. Overall, the findings position P. lilacinum COAD 4015 as a promising candidate for integrated pest and nematode management, with potential for safe and effective formulations, provided its compatibility with chemical products is carefully evaluated. Keywords: Meloidogyne; Dalbulus maidis; Spodoptera frugiperda;Rachiplusia nu; Chrysodeixis includens; Helicoverpa armigera