How do fertilizers alter plant microbes?

Transmission of B/CYDVs by aphids.


Fertilizers and other forms of nutrient inputs are important tools for agriculture, horticulture, and other plant industries. We also inadvertently increase nutrient inputs to plants through eutrophication and nitrogen deposition. While these processes feed plants, they may also indirectly feed microbes associated with plants. Because nutrients such as nitrogen and phosphorus are essential building blocks for plants and their microbes, nutrient inputs may alter plant-microbe and microbe-microbe interactions. It is unclear what the consequences of increased nutrient inputs are for plant health and microbial communities.


In my research, I explored the effects of nitrogen and phosphorus on a group of grass viruses that infect wild plants and crops – the Barley and Cereal Yellow Dwarf Viruses (B/CYDVs). My research questions included:

  • How do nutrient inputs affect the spatial patterns of B/CYDVs?
  • How do nutrients mediate within-host dynamics of B/CYDVs?
  • What are the consequences of B/CYDV interactions for disease transmission and plant health?

I completed this research as a PhD candidate in the Department of Ecology, Evolution, and Behavior at the University of Minnesota (UMN), advised by Eric Seabloom and Elizabeth Borer. We collaborated with ecologists (Charles Mitchell - UNC Chapel Hill, Alison Power - Cornell), plant pathologists (Christelle Lacroix - UMN), and mathematicians (Yang Kuang, Bruce Pell, and Tin Phan - Arizona State University). Undergraduate researchers and lab managers in the Seabloom/Borer lab that led and contributed to this research include Emily Boak, Ryan Campbell, Nicholas Cupery, Casey Easterday, Jessica Lettelleir, Timothy Martin, Tashina Picard, Kurra Renner, Luc Robichaud, Alexis Rogers, Missy Rudeen, and Anita Krause.

I used data from a field experiment conducted in California and Oregon, growth chamber experiments, and dynamical models to address these questions. Statistical approaches included generalized linear mixed-effects models, spatial correlations and cross-correlations, and Bayesian hierarchical models.

Key findings

  • Phosphorus addition and aphid vectors can cause viruses to spatially aggregate in fields (Kendig et al. 2017 Oikos).
  • Nutrient limitation and addition can promote positive interactions among B/CYDVs within hosts (Kendig et al. 2020 Ecology).
  • Co-infection can increase transmission rates of B/CYDVs (Kendig et al. 2020 Ecology).
  • Long-term nitrogen addition can ameliorate negative virus-virus interactions (Easterday et al. 2022 Ecology and Evolution).
Amy E. Kendig
Amy E. Kendig
Postdoctoral Researcher

ecologist and data scientist specializing in human impacts in plant communities