Semifield inoculative releases of the parasitoid <i>Pseudapanteles dignus</i> (Hymenoptera: Braconidae) for biological control of the South American tomato leafminer <i>Phthorimaea absoluta</i> (Lepidoptera: Gelechiidae)

Semifield trials were conducted to evaluate the efficiency of inoculative releases of the larval endoparasitoid Pseudapanteles dignus (Muesebeck), to control the South American tomato pinworm Phthorimaea (=Tuta) absoluta (Meyrick). The trials took place in experimental tomato greenhouses located in a major horticultural region of Argentina during 2018 and 2024. In 2018, three treatments were established: (i) Biocontrol 1, one mated adult female P. dignus + two P. absoluta larvae per plant; (ii) positive control, two P. absoluta larvae per plant, and (iii) negative control, uninfected plants. In 2024, the biocontrol treatment consisted of two releases of P. dignus, called Biocontrol 2, in which the initial release was carried out under the same conditions as in 2018, that is, Biocontrol 1, and the second release was carried out 30 d later, and consisted of one female P. dignus per plant. Each treatment was replicated three times. Weekly monitoring (March to April, 10 wk) was performed to record densities of P. absoluta and P. dignus (immature stages and adults) on five randomly selected plants per replicate. Besides, crop yield (number and weight of healthy fruits) and the cosmetic damage of fruits were assessed. Biocontrol 1 reduced larval and adult P. absoluta densities; in 2024, greater reductions were observed under Biocontrol 2. Although yield did not show differences across the whole experiment, cosmetic fruit damage was significantly reduced in both biocontrol treatments. These results support the potential of P. dignus as a biological control agent against P. absoluta in protected tomato production systems.