Efficacy of biological control agents, synthetic insecticides, and their combinations to control tobacco budworm [Heliothis virescens (Lepidoptera: Noctuidae)] in pigeon pea

Abstract

Tobacco budworm, Heliothis virescens (F.) (Lepidoptera: Noctuidae), is an important pest in pigeon pea [Cajanus cajan (L.) Mill.] in Puerto Rico and the tropics. The use of chemicals is the most effective strategy to control this pest. Our objective was to assess the efficacy of two biological control agents, five synthetic insecticides, and four combinations to control tobacco budworm larvae. Pigeon pea plots were sprayed with 11 insecticide treatments and water as control in 2017 and 2018. Tobacco budworm incidence and severity, and data of dry-pod/seed yield were evaluated at harvest. Plots sprayed with water, the biological control agents [Steinernema carpocapsae (Weiser) (SC), and nucleopolyhedrovirus (NP)], and chlorpyrifos had significantly higher incidences (>24%) compared with plots applied with spinetoram alone and combined with SC and NP (12–18%) in both planting years. However, there were no significant differences (P ≥ 0.05) between treatments for tobacco budworm severity (mean scores of 4.00 to 4.83 in 2017 and 2.90 to 3.60 in 2018). In contrast, significantly lower incidence (<2.00) and severity (≤2.50) were recorded with applications of chlorantraniliprole and its combination with NP and SC. However, the use of low dosages of chlorantraniliprole + NP (0.20 + 0.10 l/ha), and chlorantraniliprole + SC + oil (0.20 l + 550 g + 1.25 l/ha) increased significantly dry-pod (2.18 and 2.20 t/ha) and seed-yield (1.27 and 1.23 t/ha) only in 2017; while high dosages of β-cyfluthrin (0.20 l/ha) and chlorantraniliprole (0.30 l/ha) increased yield significantly (2.04 and 2.44; 1.72 and 1.69 t/ha) compared to the control (1.25 and 0.76 for dry-pod; and 0.78 and 0.26 t/ha for seed in 2017 and 2018, respectively). We concluded that timely applications of β-cyfluthrin and chlorantraniliprole may increase net incomes over $4000/ha and should be incorporated in insecticide rotations to control tobacco budworm in pigeon pea.