Plant probiotics? Understanding how soil health practices influence plant-insect interactions

2016 Annual Report for GNE16-135

GNE16-135 (project overview)
Project Type: Graduate Student
Funds awarded in 2016: $15,000.00
Projected End Date: 04/30/2018
Grant Recipient: Penn State University
Region: Northeast
State: Pennsylvania
Graduate Student:
Elizabeth Rowen
Email
Faculty Advisor:
Dr. John Tooker
Email
Penn State

Plant probiotics? Understanding how soil health practices influence plant-insect interactions

Summary

I started objectives 1 and 2 over the summer of 2016, including collecting soils from farmer-collaborators, and setting up first year of the manure experiment and collecting predator and plant damage data for objective 2. For objective 1, I set up 2 experiments to examine the effects of microbial community from different soils on herbivore performance. Through this experiment, it was determined that sterilizing soils using steam treatments changed the nutrient content of the soil and researchers were unable to determine if effects on plant growth and herbivore performance were due to nutrient differences in the soil or the microbial community. Because of this, we plan to adjust methods to better sterilize soils (by using a filtration technique to separate microbial communities). Objective 2 was started in June 2016, earlier than anticipated to have another year of data, and have collected predator community, early season pest damage data and silage yield data. We have also adjusted objective 2 by adding a cover crop treatment in addition to the manure treatment in a factorial design to isolate the effects of manure and cover crops on organic matter accumulation and soil health on insect pests/predator communities. This cover crop was planted in October 2016. 
 

Objectives/Performance Targets

Objective 1: Using farm-collected soils with different agronomic histories, I will measure the effect of microbial communities on plant resistance.
  • Pre-SARE award:
    • collected soils from 4 farms = 6 soils total in OH and PA 
    • Soil analysis at PSU soil lab 
    • Pasteurized soils and grew corn to feed to black cutworm caterpillars. Measured plant growth, herbivore performance (mass gain) on each treatment (±microbes), we found that nutrient difference due to sterilization technique was a problem. We are planning to sterilize using a filtration technique rather than just using a steam treatment. 
  • since SEPT
    • Repeated caterpillar experiment with reduced number of soils and found similar effects of microbes on caterpillar performance as first experiment. 
    • measured soil respiration with collaboration from Charlie White and Jason Kaye
    • Extracted DNA from soil samples and sent for Illumina sequencing with collaboration with Charlie Mason and Kelli Hoover
    • Found Commercial lab that does PLFA testing that is much more economical and efficient for the low number of samples that we have – Ward Laboratory  ($60/soil samples)
Objective 2: I will evaluate how nutrient management with organic-matter rich amendments (manure/compost) or inorganic fertilizers affects insect damage, predator communities, and yield.
  • Pre SARE
    • Set up year 1 of manure experiment
      • collected pitfall predator samples 1/month June-Sept 2016 – have processed and identified June samples 
      • Measured early season damage – no difference between manure and inorganic treatments 
      • Measured caterpillar performance on tissue from manure and inorganic treatments – no differences, but assay needs refinement because of high larval mortality. 
      • Measured yield – manure had lower yields than inorganic, likely due to lower emergence early in season in manure plots. 
      • Planted a cover crop in a second factorial treatment Oct 2016 (winter wheat that will have red clover frost seeded into it in February 2017). 
Objective 3: I will share results with extension educators and farmers around Pennsylvania.
  • Shared preliminary results of OBJ 1 at the International Congress of Entomology in Orlando, FL

Accomplishments/Milestones

Year 1 of soil microbial experiment, including getting soil DNA extracted for bacterial and fungal community analysis. We found that the methods outlined in the original proposal have problems because the sterilized and unsterilized soils have different nutrient content, thus we found another way to isolate the effects of nutrients from microbes on the plants. Money was only awarded to the university as of Dec 13, 2016, thus all work so far has been accomplished using other grants. 
 

Impacts and Contributions/Outcomes

Soil health practices, such as cover cropping and reducing tillage, improve physical characteristics of soil, but also appear to increase microbial community diversity. Importantly, by changing the nutritional quality or anti- herbivore defenses of host plants, some soil microbiota can influence the damage that insect herbivores cause to plants. However, research in this area has typically focused on particular microbial inoculants. We proposed to take a community approach encompassing microbes (bacteria and fungi) and natural enemies of insect herbivores to examine how agronomic practices influence beneficial organisms that can modulate levels of damage by plant-feeding insects. This work is fundamental for understanding how insect crop damage may be affected by soil health practices, and will provide insight for farmers about how management practices meant to improve soil quality can also decrease risks from plant-feeding insects.
 

Collaborators:

Dr. John Tooker

tooker@psu.edu
Associate Professor
Pennsylvania State University
001 Merkle Lab
University Park, Pennsylvania 16802
United States
Office Phone: 814-865-7082
Website: http://ento.psu.edu/research/labs/john-tooker
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