Prayan Pokharel - PhD

Research

Physiological and ecological implications of chemical defense in insects

My research work is based on the conceptual framework of plant-insect coevolution, mainly in the uptake and use of plant toxins by herbivorous insects (i.e., sequestration) as a defense against biological antagonists. But the physiological and ecological implications of toxin sequestration in the milkweed bugs (Heteroptera: Lygaeinae) is largely unknown. Therefore, I investigate the mechanisms underlying the costs of sequestration of dietary toxins (here, cardenolides), and try to understand the ecology and evolution of these physiological processes.

 

Effects of plant nutrition and seeding techniques on insect pests and natural predators

Since chemical synthetic pesticides have a negative impact on the environment and on human health, future agriculture needs to be based on alternative practices. One of the promising strategies is to support beneficial insects that carry out natural pest control. But the effect of plant nutrient supply and seeding regimes on both pest and beneficial insects remains unresolved. Therefore, under the realm of NOcsPS regimes, I investigate the abundance of total insect biodiversity (including pest and beneficial insects), growth and development of insect pests, and predator efficiency of beneficial insects against pest insects.

Contact

Otto-Sander-Str. 5
Altbau Phytomedizin
Raum 173

Tel: 0049(0)711-459-24663
prayan.pokharel@uni-hohenheim.de

Projects

2017 - present: Differential processing of host-plant toxins by insect herbivores as a driver of multi-trophic interactions

  • Estimate physiological costs of cardenolide sequestration using feeding assays and chemical analysis
  • Study predator-prey interaction using predation trials

2022 - present: NOcsPS (Agriculture 4.0 without Chemical-Synthetic Plant Protection) Project

  • Record insect populations across all agricultural crops using sweep nets
  • Conduct growth and fecundity assays on selected insect pests directly in the field using closed system tools such as clip-cages
  • Assess the efficiency of natural pest control by predators and parasitoids

Curriculum vitae

 

[Dec 2022-present]
Postdoctoral Scientist, Department of Applied Entomology, Institute of Phytomedicine, University of Hohenheim, Stuttgart, Germany. Project: Agriculture 4.0 without Chemical-Synthetic Plant Protection, Consortium Partner: Effect of plant nutrition and seeding technique on insect pests and natural predators.
[Jan 2018-Nov 2022]Doctorate of Natural Sciences (Dr. rer. nat.), Faculty of Natural Sciences, University of Hohenheim, Stuttgart, Germany. Doctoral Thesis: Physiological and ecological implications of sequestered cardenolides in the milkweed bugs (Heteroptera: Lygaeinae). Supervisors: Prof. Dr. Georg Petschenka, Prof. Dr. Anke Steppuhn & Prof. Dr. Volkmar Wolters
[Oct 2014-Oct 2016]

Agrobiotechnology (MSc), Justus Liebig University Giessen, Germany. Master's Thesis: Antimicrobial properties of bacterial communities in the feces of stored food pest insects. Supervisors: Dr. Gerrit Joop & Prof. Dr. Andreas Vilcinskas


 

   

Publikationen

  • Scientific Publications

Pokharel, P. "No-cost meals might not exist for insects feeding on toxic plants." Biology Open 2023, 12 (6). https://doi.org/10.1242/bio.059800

Heyworth, C*; Pokharel, P*; Blount, JD; Mitchell, C; Petschenka, G; Rowland, H. "Antioxidant availability trades off with warning signals and toxin sequestration in the large milkweed bugs (Oncopeltus fasciatus)" [*Authors contributed equally]. Ecology and Evolution 2023, 13, e09971. https://doi.org/10.1002/ece3.9971

Pokharel, P. "Physiological and ecological implications of sequestered cardenolides in the milkweed bugs (Heteroptera: Lygaeinae)." PhD Thesis, University of Hohenheim 2023. http://opus.uni-hohenheim.de/volltexte/2023/2113/

Jeckel, AM; Beran, F; Züst, T; Younkin, G; Petschenka, G; Pokharel, P; Dreisbach, D; Ganal-Vonarburg, SC; Robert, CAM. "Metabolization and sequestration of plant specialized metabolites in insect herbivores: Current and emerging approaches." Frontiers in Physiology 2022, 1905. https://doi.org/10.3389/fphys.2022.1001032

Pokharel, P; Steppuhn, A; Petschenka, G. "Dietary cardenolides enhance growth and change the direction of fecundity-longevity trade-off in milkweed bugs (Heteroptera: Lygaeinae)" Ecology and Evolution 2021, 11, 18042–18054. https://doi.org/10.1002/ece3.8402

Pokharel, P; Sippel, M; Vilcinkas, A; Petschenka, G. "Defence of milkweed bugs (Heteroptera: Lygaeinae) against predatory lacewing larvae depends on structural differences of sequestered cardenolides" Insects 2020, 11, 485. https://doi.org/10.3390/insects11080485

  • Popular Science Articles

Pokharel, P. "Addressing Climate Justice in Schools." My Republica, https://myrepublica.nagariknetwork.com/news/addressing-climate-justice-in-schools/?categoryId=opinion Published 15 June 2023

Pokharel, P. "Conservation of insects." The Kathmandu Post, https://kathmandupost.com/columns/2022/07/09/conservation-of-insects Published 9 July 2022

Pokharel, P. "Female scorpions pay a steep cost when they shed their tails for survival." Massive Science, https://massivesci.com/notes/scorpion-limb-loss-tail-mating/ Published 23 February 2021

Pokharel, P. "Should society trust science?" Crastina, https://crastina.se/the-crastina-microessay-competition-2020/winners/ Published 09 December 2020

Pokharel, P. "Whiteflies evolved to disarm plants' defenses with sugar." Massive Science, https://massivesci.com/notes/whitefly-insects-pest-agriculture-sugar/ Published 31 October 2020

Pokharel, P. "Though smelling sweet, linden trees are bad for bumblebees." Massive Science, https://massivesci.com/notes/linden-trees-are-bad-for-bumblebees-toxic-starvation/ Published 14 August 2019

Pokharel, P. "Insects are nature's little helpers." The Kathmandu Post, https://kathmandupost.com/columns/2019/08/06/insects-are-nature-s-little-helpers Published 06 August 2019

Pokharel, P. "Fall armyworms have come to Nepal from America, and they can trouble maize farmers here." Onlinekhabar, https://english.onlinekhabar.com/fall-armyworms-have-come-to-nepal-from-america-and-they-can-trouble-maize-farmers-here.html Published 25 June 2019

Pokharel, P. "Caterpillars: The Masters of Mimicry." Euro Scientist, https://www.euroscientist.com/caterpillars-the-masters-of-mimicry/ Published 4 October 2018

Pokharel, P. "Why Some Fireflies Become Femme Fatales in Their Race for Survival." The Conversation, http://theconversation.com/why-some-fireflies-become-femme-fatales-in-their-race-for-survival-91252 Published 7 February 2018

Pokharel, P. "The Hidden Secrets of Insect Poop." The Conversation, http://theconversation.com/the-hidden-secrets-of-insect-poop-81908 Published 8 August 2017

Pokharel, P. "'Himalayan Viagra' Is Threatened by Fervent Chinese Demand and Climate Change." The Conversation, http://theconversation.com/himalayan-viagra-is-threatened-by-fervent-chinese-demand-and-climate-change-78558 Published 5 June 2017