Method for generating optimal attractive scents for Asian Citrus Psyllid (ACP) biocontrol

Research by: University of Connecticut and University of Florida

Article written by: Dr. Alexander Aksenov
Article edited by: Ed Stover, Lukasz Stelinski, Peggy G. Lemaux

What is the research?

Frequent insecticide sprays have been used to suppress the HLB-pathogen’s insect vector, the Asian citrus psyllid (ACP). A far better strategy would be to use chemical lures to capture and kill the insects. Unfortunately, pheromones, secreted chemicals that act like hormones to affect the behavior of other insects, do not appear to attract ACP. Complex mixtures of volatile organic compounds (VOCs), mimicking citrus plant aromas, show some promise as attractants, but insect behavior changes with minor shifts in specific concentrations of these compounds. Using simple mixes of VOCs are not sufficiently attractive to ACP and controlled dispersal of more than a few compounds is technically challenging. To address this situation, we will optimize complex ACP-attractant VOCs, dispersed via newly developed materials, made out of a polymer support material interspersed with graphene (a conductive material made of a single layer of carbon atoms), that can capture and fix the VOCs. This material can deliver flexible, controlled mixtures of VOCs to optimize their attractiveness and can be used to disperse ACP attractants in citrus orchards. The goal of this research is to improve the attract-and-kill (AK) approach for ACP by optimizing the attractant, using the approach described below.

What are some of the major successes to date?

Stelinski and colleagues developed an AK trap, using ACP-sensory responses, that are based on their look, feel and taste,­­ and optimized trap components in greenhouse and simulated field conditions. Multiple sensory cues are used to attract psyllids to a cylindrical trap that has visible and UV colors, chemical attractants and compounds that attract pests and also contain a toxicant. The trap will be enhanced with a stimulant that mimicks complex citrus scents and that is dispersed using a novel volatile-release device with a single layer of carbon atoms (graphene), developed by the Adamson group (Figure 1). The graphene surface acts as an adsorber that controls compound release. Short current pulses are passed through the graphene, to heat the surface precisely to achieve controlled release of the compounds. By utilizing multiple graphene capsules, each with a controller, release of each compound can be precisely controlled.

Who is working on this project?  

Alexander Aksenov, Douglas Adamson, Ali Bazzi from the University of Connecticut; Lukasz Stelinski from the University of Florida.

What are the challenges and opportunities?

The team has completed 0.5 years of a two-year project. We optimized the graphene composite manufacturing procedure to ensure consistent, reproducible properties. We extensively characterized release of individual VOCs from graphene. An initial, beta version of the device is being assembled to begin testing attraction on live insects. An anticipated challenge will be delivering sufficient numbers of devices per area of crop that can manage ACP populations under natural conditions. Manufacturing these materials could be scaled to produce an economically viable product because the cost of materials is relatively low.

Funding source: USDA-National Institute of Food and Agriculture (NIFA) - Citrus Disease Research and Extension Program # Grant USDA-NIFA-SCRI-009111

Figure 1. Novel, low-cost graphene composite at progressively greater magnification. Starting from the rigid open cell foam on the left, greater magnification reveals the foam's individual cells after removing the water. Further magnification shows holes or "windows", that create a porous network that connects to cells underneath. Final magnification (far right) shows individual graphene sheets on the interior surface of a cell.