Plant signaling compounds to manage huanglongbing vector in citrus groves

Overview

Huanglongbing (HLB), also known as citrus greening disease, is one of the most devastating threats to commercial citrus production worldwide. It is spread primarily by the Asian citrus psyllid (Diaphorina citri), which locates citrus trees using a combination of visual and scent cues. This research proposes the use of two plant signaling compounds, Methyl Jasmonate (MJ) and Salicylic Acid (SA), applied as foliar sprays to modulate the volatile emissions of citrus trees and thereby reduce psyllid colonization in commercial groves.

Preliminary work by Dr. Joseph Patt (USDA) demonstrated that MJ application lowers the proportion of methyl salicylate (MeSA) emitted by HLB-infected trees. Because MeSA is a key attractant for D. citri, suppressing its emission could discourage psyllid settling during shoot flush, a critical period for HLB transmission. MJ also enhances emission of volatiles that attract natural enemies of the psyllid, adding a biological control dimension. SA-treated trees showed different volatile profiles dominated by MeSA, suggesting both compounds could be combined in a push-pull pest management strategy.

Technical specifications

Approach:

• Foliar spray application of Methyl Jasmonate and Salicylic Acid at low and high concentrations to citrus foliage
• Comparison of psyllid settling and aggregation on healthy versus HLB-infected trees
• Measurement of MeSA and other key volatile organic compounds emitted from treated foliage using gas chromatography-based methods
• Evaluation of dose-response relationships between compound concentration and psyllid foraging behavior
• Time-course analysis of volatile emissions over several days to assess durability of the effect

Key findings from prior research:

• MJ-treated HLB-infected trees emitted lower proportions of MeSA compared to controls
• MJ enhanced emission of volatiles attractive to psyllid natural enemies
• SA-treated trees showed volatile profiles dominated by the psyllid attractant MeSA
• Observed effects were short-lasting, motivating further study of dose and timing

Potential applications:

• Integrated pest management for citrus groves affected by HLB
• Push-pull strategies combining repellent and attractive volatile cues
• Reduced reliance on broad-spectrum insecticides in citrus production

Technology readiness level

The research is at an early experimental stage (TRL 2–3). Prior proof-of-concept work has demonstrated that MJ and SA application alters citrus volatile profiles and influences psyllid colonization in controlled settings. The proposed validation will systematically test dose effects, durability of volatile changes, and psyllid behavioral responses on both healthy and HLB-infected trees. Further field-scale trials and formulation optimization would be needed before commercial deployment.