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Bugs like sweet corn as much as consumers

  • UMES entomologist embarks on search for safe ways to fend off insect pests

    Thursday, August 6, 2020
    Dr. Simon Zebelo

    It's that time of year when summer fields are filled with mouth-watering local sweet corn.

    A "Capacity Building Grant" from the U.S. Department of Agriculture's National Institute of Food and Agriculture worth nearly $600,000 was awarded to Dr. Simon Zebelo, a University of Maryland Eastern Shore researcher, to help expand sustainable sweet corn production on Delmarva.

    Zebelo, an associate professor and entomologist with UMES' Department of Natural Sciences, will spend the next three years on the research project, which aims to develop organically based, integrated pest management of corn earworm, a major insect pest for sweet corn.

    “We plan to design and educate growers about integrated pest management programs that simultaneously manipulate insect herbivores, weeds and beneficial arthropods that affect sweet corn,” Zebelo said.

    Sweet corn was chosen as the test crop, he said, because of its economic importance to diverse farming operations -- and preliminary investigations displaying its compatibility with plant growth promoting rhizobacteria, minimum tillage and cover cropping.

    Leaves of sweet corn that have been treated with plant growth promoting rhizobacteria, damaged by insects, mechanically damaged and untreated, will be collected.  Four biological replicates will be collected for each treatment combination. 

    Total RNA (ribonucleic acid) will be extracted from leaf samples to characterize and qualify the changes of defense-related genes that regulate direct and indirect defenses.  Corn earworm eggs will then be placed on a sweet corn leaf from plants inoculated with various plant growth-promoting rhizobacteria (PGPR) treatments in a Petri dish, which will be placed in an incubator.  After larvae hatch, the fate of a single neonate larva on each leaf will be followed until death, or moving to an interim step in development before maturing into an insect.       

    To “quantify the efficacy of promising PGPR strains tested in the first experiments,” sweet corn will be placed in micro-plots (pots using field soil) in low-tunnel houses to examine treated and untreated plants for egg-laying choice by the females.

    “Our preliminary data show that the European corn borer can differentiate between PGPR-treated corn plants, and deposits more eggs on untreated plants,” Zebelo said.

    The next step is to determine the effects of minimum tillage and using cover crops on weed and insect pests, natural enemy effectiveness and sweet corn yield, he explained.  Field experiments will be conducted during two seasons in Maryland.  During early fall, crimson clover, forage radish and rye will be combined and planted in conventional till and no-till plots. 

    Red clover with rye and red clover with forage radish biocultures will be planted in alternating rows in living mulch plus cover crop residue and living mulch plus winter-killed residue.  Subplot treatments will include herbicide and no herbicide applications.

    During the spring, cover crops in conventional till plots will be mowed, plowed and disked under.  Crimson clover deteriorates naturally in spring and forage radish will winter-kill, Zebelo said.  A roller-crimper will be used to terminate the rye in no-till and living mulch plus cover crop residue and temporarily slow red clover growth in living mulch plots. 

    In mid-to-late May, sweet corn will be seeded into each plot.  Weed biomass and density, along with timed weed removal data, will be collected, identified to species, counted and the percentage of area utilizing cover crop, weed and bare-ground estimated.

    According to Zebelo, the teaching component underwritten by the grant involves a partnership between the University of Maryland College Park and UMES to teach a new weed science course to UMES students.  As part of  UMES Extension outreach, workshops for farmers on integrated pest management also will be held to: increase awareness and adoption of the three-level hierarchical approach for pest management recommended by the National Organic Program, demonstrate the effectiveness of alternative pest management tactics developed in the field experiments, provide educators and farmers training in applied pest management tactics and create awareness of the benefits using minimum tillage and cover crops.

    Zebelo holds a doctorate in plant and environmental bio-sensory chemical ecology from the University of Turin, Italy and a master's in agricultural entomology from the Hawassa University in Ethiopia.  His research interests include: fundamental and applied aspects of plant-insect interactions, insect behavior, chemical ecology and integrated pest management. 

    This work is federally funded by the USDA/NIFA Capacity Building Grant Program (Grant No. 2019-03188). 


    Gail Stephens, agricultural communications and media associate, School of Agricultural & Natural Sciences, University of Maryland Eastern Shore, 410-621-3850, gcstephens@umes.edu.