Determination of an Economic Injury Level for Old World Bollworm (Lepidoptera: Noctuidae) in Processing Tomato in Brazil

Tomato plants host various herbivores, including the Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), recently introduced into South and Central America. It is a harmful pest for tomato crops, damaging mainly the flowers and fruits. The assessment of losses and the establishment of economic injury level (EIL) and economic threshold (ET) are core steps toward establishing a control program. We determined losses caused by H. armigera on processing tomato and estimated EIL/ET values. Trials were run during two growing seasons using tomato plants caged in the field. The field cage experiment consisted of six densities of H. armigera second instar larvae (0, 1, 3, 6, 12, and 24 larvae per row meter) at two infestations periods spaced 15 d apart with the first infestation done 90 d after transplanting. The larvae were placed individually on the third upper fully developed leaf. The number of healthy and damaged fruits, size, and weight of the fruits were measured. Yield losses as a function of infestation of 1–24 larvae per row meter ranged from 4 to 34% and resulted in a yield reduction of 1.22–12.77 kg per row meter. The EIL ranged from 1.41 to 1.72 and from 2.11 to 2.58 larvae per row meter of plants in 2017 and 2018 cropping seasons, respectively. Helicoverpa armigera causes significant reduction of tomato yield. These EIL values will enable better control decision-making in processing tomato.