Viability of using Murraya paniculata as a trap crop to manage Diaphorina citri and huanglongbing in citrus

Abstract

Trap cropping is a sustainable control method aimed at reducing pest insect populations in main crops. In this study, the effect of insecticide-treated Murraya paniculata as a trap crop to reduce Diaphorina citri populations and huanglongbing (HLB) incidence was evaluated in a large area of a commercial citrus orchard. Additionally, the economic viability of this tactic and the flushing pattern and synchrony of M. paniculata and sweet orange trees were assessed. The experiment was conducted in a randomized block design, with four blocks (4.5 ha each) located at the orchard border. Each block contained two treatments: 1) M. paniculata trap crop treated with insecticides (with trap crop) and 2) absence of M. paniculata trap crop (without trap crop). The average psyllid population and cumulative HLB incidence in the plots with trap crop (0.1 psyllids/yellow stick card/fortnight and 2.1% symptomatic trees) were ≈31% lower than in plots without trap crop (0.14 psyllids/yellow stick card/fortnight and 3.1% symptomatic trees). The number of new shoots/branch was higher in M. paniculata than in citrus trees in 83% of the assessment dates. The trap crop tactic becomes viable when HLB incidence exceeds 4.5% for orchards with trees younger than three years, and 17.1% for orchards with trees between three and 5.5 years of age. Therefore, this study confirms that M. paniculata can be used as a trap crop for managing D. citri and HLB; however, its economic viability depends on disease incidence.