Evaluation of Leaf Consumption and Determination of Economic Injury Level Caused by Plutella xylostella (L.) (Lepidoptera: Plutellidae) in Brassica oleracea var. acephala (Brassicales: Brassicaceae)

摘要

Plutella xylostella (L.) is a microlepidopteran found in all brassica-producing regions of the world. However, no economic injury level (EIL) has been established for this pest in collard greens. Therefore, studies evaluating the EIL of P. xylostella in this crop based on the number of caterpillars per plant can assist pest monitoring and the most effective time for pest control, ensuring profits and the use of pesticides only when required. The present study assessed leaf consumption of caterpillars at different levels of infestation and determinined the EIL for P. xylostella in collard greens. Based on the yield reduction index of collard greens for P. xylostella, EIL was estimated for different scenarios of pest control costs, setting the market value of the bunch of collard greens, and, alternatively, with prices varying and the control cost fixed. In simulated scenarios for 7 d after infestation, the number of caterpillars per plant was always below 1.38, whereas for 10 d, the maximum number was 1.25 caterpillars per plant. When simulating scenarios with different market values for the bunch of collard greens the lower the price of the collard greens bunch, the higher the mean number of caterpillars per plant to compensate the application cost. The mean number of caterpillars per plant ranged from 4.59 to 0.38 in the evaluation for 7 d, and from 4.17 to 0.35 caterpillars per plant for 10 d according to the price of the bunch of collard greens.