Enhancing biological control in Eucalyptus by optimizing Tenebrio molitor L. (Coleoptera: Tenebrionidae) mass rearing

The biological control of insect pests in eucalyptus cultivation has been an important strategy. However, its efficacy faces challenges in keeping up with the rapid expansion of planted areas in Brazil. Among the challenges are the large-scale releasing methods and, most importantly, scaling up mass rearing of natural enemies in the laboratory. Thus, the objective of this work was to optimize the mass rearing of Tenebrio molitor, L. (Coleoptera: Tenebrionidae), an essential component in the biological control of eucalyptus defoliating caterpillars in Brazil. Our aim was to enhance the production of T. molitor pupae, which are used as an alternative host for Palmistichus elaeisis Delvare & LaSalle (Hymenoptera, Eulophidae) and as a source of nutrition for the predators of the Podisus genus. Both are utilized as natural enemies in biological control programs for eucalyptus defoliating caterpillars. Over a two-year period, the mass rearing process of T. molitor at Bracell, a cellulose company, underwent various optimization stages. These included the strategic separation of adult and larval stages in different rooms, accompanied by tailored temperature control, enrichment of the diet with additional sources of carbohydrates and proteins, streamlining operational processes using the lean methodology, and adapting a vibrating table for pupae collection. These optimizations resulted in a remarkable 530% increase in the total number of T. molitor pupae produced annually. Subsequently, the optimized mass rearing yielded a substantial number of individuals of Podisus sp. (257,235) and P. elaeisis (over 62 million), sufficient for the successful biological control of defoliating caterpillars on 9,277 hectares of eucalyptus. The optimizations carried out in the mass rearing of T. molitor resulted in significant gains in Bracell's defoliating caterpillar biological control program, making it the primary method of caterpillar control used by the company.