Evaluation of Oilseed Radish Biomass Management As A Control Strategy For Pests In No-Till Corn

Project Overview

FNC14-979
Project Type: Farmer/Rancher
Funds awarded in 2014: $7,354.00
Projected End Date: 12/31/2015
Region: North Central
State: Wisconsin
Project Coordinator:

Annual Reports

Commodities

  • Agronomic: corn

Practices

  • Pest Management: botanical pesticides

    Summary:

    This project is investigating the efficacy of radish biomass management on slug and nematode populations and the impact on yield of no-till corn.

    Use of improved, proprietary varieties of oilseed radish such a “Tillage” and “Groundhog” for cover crops has seen explosive growth and presumably has contributed to sustainability by positively affecting soil and water quality. However, experience indicates the potential for negative pest interactions, specifically the ability of radishes to create ideal habitat for slugs. These pests can devastate stands of subsequent crops, especially under no-till conditions, and there’s no reliable control method.

    Radishes may contain a built-in control method for slugs if managed for this purpose. As members of the mustard family, they produce glucosinolates which are converted to allyl-isothiocyanate upon plant decomposition. Mechanical disruption of cells (such as chopping the cover crop) may produce lethal concentrations of allyl-isothiocyanate to reduce pest populations. This is a common component of biofumigation, but is frequently followed by incorporation of plant residues and commonly, sealing the soil surface with plastic. Common wisdom and to a lesser extent, science suggests this step is necessary to maintain concentrations of the mustard gas due to its volatility. Incorporation of residues also requires tillage so is at cross purposes to no-till production. It’s also possible that destruction of ideal slug habitat may reduce over-wintering populations and egg production. This may be the case where vegetation is chopped, allowing the biomass and soil surface to dry.

    In field trials, we are investigating the impact of radish management on pest populations, soil protection and corn performance. Treatments following wheat harvest include no cover crop, unmanaged radish and radish-managed (chopped with a flail chopper in early November). From the one and one-half experimental cycles completed we’ve found chopping radish with a flail chopper produces a uniform residue mat on the surface and post planting (corn) residue is similar between chopped and unchopped residue. Additional cycles will be completed over the next two years to further determine efficacy against pests.

    Introduction:

    Use of improved, proprietary varieties of oilseed radish such a “Tillage” and “Groundhog” for cover crops has seen explosive growth in the past few years and industry representatives claim millions of acres are planted in the upper mid-west in any given year (J. Simon, Partners in Progress Seed, Sun Prairie, WI, personal communication). Undoubtedly this growth in cover crop use has benefited the sustainability of agriculture by positively affecting soil quality, but experience indicates the potential for negative pest interactions, specifically the ability of radishes to create ideal habitat for slugs. These pests can devastate stands of subsequent crops, especially under no-till conditions, and we don’t have reliable control methods other than avoidance and helping the new crop out-grow its period of susceptibility early in the growing season.  Rank fall growth maintains high relative humidity under the canopy, creating an ideal environment for slug growth and reproduction, the mustard family in general is a known host for slugs and the nature of the vegetation may create an ideal over-wintering habitat.

    Radishes may contain a built-in control method for slugs if managed for this purpose. All members of the mustard family produce glucosinolates which are converted to allyl-isothiocyanate upon plant decomposition. This chemical is similar to methyl iosthiocyanate, the active ingredient in the chemical fumigant Metam Sodium which is routinely used a biocide in vegetable production. Conversion of glucosinolates to allyl-isothiocyanate is a purely chemical reaction and depends on cell rupture. This happens naturally as tissues decompose but the concentration of allyl-isothiocyanate may be too low to produce lethal effects on target organisms with natural decomposition. Also, glucosinolates are only produced in green material, not plant roots so the impact on soil-dwelling pests may be minimal.

    Mechanical disruption of cells (such as chopping the cover crop) may produce lethal concentrations of allyl-isothiocyanate to reduce pest populations. This is a common component of biofumigation, but is frequently followed by incorporation of plant residues and commonly, sealing the soil surface with plastic. Common wisdom and to a lesser extent, science suggests this step is necessary to maintain concentrations of the mustard gas because it’s highly volatile. Incorporation of residues requires tillage so is at cross purposes to no-till production.

    It’s also possible that destruction of ideal slug habitat may reduce over-wintering populations and egg production. This may be the case where vegetation is chopped, allowing the biomass and soil surface to dry.

    Project objectives:

    1. To determine if manipulated (chopped) radish cover crop residues suppress slug and nematode populations and their damage to the subsequent corn crop;
    1. To determine if manipulation (chopping) of the radish cover crop reduce its ability to protect the soil overwinter (does it reduce the conservation performance of the cover crop?)
    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.