​Research Overview

​The focus of Nachappa lab is plant virus-insect vector interactions and pest management. The two key questions of our research program are: (1) how do plant pathogens affect biology and behavior of their insect vectors and (2) what plant or insect factors mediate manipulation of insect vectors by plant pathogens? Our lab is interested in understanding these interactions as a means of managing plant pests and diseases. 

Below is an overview of our current projects involving hemp:

Current Hemp Projects:

As the production of hemp increases across the United States, so have the challenges in pest and disease identification and management. We have several projects related to emerging pest and disease identification and management in hemp:
​Building Resilient Pest Management Strategies for Organic Hemp Systems

​The long term goal of this project is to create a robust organic hemp production system resilient to arthropod pests, which will provide local growers with management tools to improve crop health and sustainability. This goal will be accomplished through four objectives: 
  1. Quantify the effects of organic production systems on plant resistance to hemp pests through changes in rhizosphere microbiome.
  2. Evaluate hemp cultivars for resistance to hemp pests in organic production systems.
  3. Determine the effectiveness of OMRI-approved insecticides in combination with biological control for suppression of hemp pests.
  4. Develop effective methods to provide research-based information to hemp growers and other stakeholders.
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Adult cannabis aphid. Image credit: Whitney Cranshaw, Bugwood.org
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Winged adult cannabis aphid. Image credit: Whitney Cranshaw, Bugwood.org
Epidemiology And Management Of Beet Curly Top Virus, An Emerging Vector Borne Virus Of Hemp In Western U.S.
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​Curly top disease, caused by beet curly top virus (BCTV), has recently been identified as as an emerging disease affecting hemp in the western United States. There is a strong need to identify the drivers of emergence and establishment of BCTV in hemp to reduce disease impact. 

The long term goal of this project is to develop a better understanding of BCTV epidemiology in hemp and identify disease mitigation strategies. This will be accomplishment through the following objectives:
  1. Characterize (a) beet leafhopper vector dynamics, (b) incidence and diversity of BCTV strains, and (c) timing of BCTV infection in hemp.
  2. Evaluate the impact of host plant resistance and cultural practices on reducing BCTV incidence, yield reduction, and quality loss.
  3. Develop effective methods to provide research-based information to hemp growers and other stakeholders. 
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Hemp plant infected with BCTV. Image credit: Whitney Cranshaw, Bugwood.org
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Adult beet leafhopper. Image credit: A.C. Magyarosy, Bugwood.org
Biology And Management Of Hop Latent Viroid, An Emerging Pathogen Of Hemp
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As an emerging hemp pathogen, hop latent viroid (HLVd) has the potential to cause significant damage and crop loss. The long term goal of this project is to assess the impact and vector transmission of HLVd in hemp. This will be accomplished through the following objectives:
  1. Determine the modes of HLVd transmission by arthropod vectors, pollen, and seed.
  2. Determine the effect of induced chemical resistance in reducing HLVd symptom development and infection levels.
  3. Develop effective methods to provide research-based information to hemp growers and other stakeholders.
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Plant infected with HLVd. Image credit: Zamir Punja, Simon Fraser University
Examining the Adaptive Roles of Plant Defensive Chemistry on Pest Resistance in Cannabis sativa

Cannabis sativa is known for the presence of cannabinoids, which include Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), and more than 100 related secondary metabolites. In addition to cannabinoids, C. sativa also possesses a range of defense mechanisms (namely terpenes and phenolic compounds) that are conserved across dicots and well described in other model plant species.

​The primary goal of this project is to determine how variation in these cannabinoids affect key hemp pests. The secondary objectives of this project are to:
  1. Quantify the performance of key hemp pests and cannabinoid content on a population of 200 recombinant inbred lines (RILs).
  2. Identify candidate genes involved cannabinoid content and pest resistance.
  3. Evaluate the functional role of the candidate pest resistance genes.​
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Two hemp leaves; One heavily damaged by hemp russet mites (left) and the other healthy (right). Image credit: Whitney Cranshaw, Bugwood.org
Examining the Effects of Pesticide Treatments on Pest Populations, Cannabinoid Concentrations, and Pesticide Residues in Cannabis Sativa

The primary goal of this project is to investigate the interaction between application of pesticides on pest populations, persistence of chemical residues in the cannabis flowers, and metabolic shifts in the cannabinoid profiles. This will be accomplished through the following objectives:
  1. Quantify the effects of individual hemp pesticides on: pest populations, plant parameters, cannabinoid profiles, and pesticide residues in the inflorescence yield.
  2. Quantify the effects of mixed application on the above listed factors in the inflorescence yield.
  3. Examine the effect of the timing of the last pesticide application on the cannabinoid profile and on residual contamination at harvest. 
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Corn earworm feeding on a hemp flower bud. Image credit: Britt et al 2021, Journal of Integrated Pest Management