Influence of biotic and abiotic factors on the population fluctuation of Tuta absoluta (Lepidoptera: Gelechiidae) in an organic tomatofarming

The tomato leafminer, Tuta absoluta (Meyrick, 1917), is an important pest of tomato in South America, and has been reported in many countries in Europe and the Middle East. The population fluctuation of this species was examined during three consecutive crop years, in a commercial organic greenhouse in southeastern Parana, subtropical region of Brazil. The T. absoluta abundance was evaluated in the tomato Cordilheira variety during the three crop years, along with TO60 cultivar in the first and Pizzadoro in the last two periods evaluated. Larvae and pupae of T. absoluta were collected; pest threshold levels were not reached in any of the crop years examined. A stepwise multiple regression revealed that minimum and mean temperature were factors that significantly affected the abundance of the tomato leafminer. The peaks of abundance coincided with high previous temperatures. Larval T. absoluta density was highest during the fruiting stage and the abundance was highest on the Cordilheira variety in all seasons and during the three crop years. Four species of parasitoids distributed in three families of the order Hymenoptera were found: Conura sp. Spinola, 1837 (Chalcididae), Earinus sp. Wesmael, 1837 (Braconidae), Myosoma sp. Robertson, 1900 (Braconidae), and Casinaria sp. Holmgren, 1859 (Ichneumonidae). The latter two are cited for the first time parasitizing T. absoluta. Based on the low level of infestation of the species, our findings demonstrate that the lower temperatures prevent T. absoluta from becoming a major pest in the evaluated region, characterized by subtropical climate.