Submitted to: Sugarbeet Research and Extension Reports
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/1/2003
Publication Date: 5/1/2003
Citation: Majumdar, A., Boetel, M.A., Jaronski, S., Dregseth, R.J., Schroeder, A.J. 2003. Integration of an entomopathogenic fungus and cereal cover crops for sugarbeet root maggot management. Sugarbeet Research and Extension Reports. 34:198-204. Interpretive Summary: This paper reports on two years of field trials on combining Metarhizium anisopliae with oat or rye cover crops in sugar beets to manage damage from the sugarbeet root maggot. In the face of a moderate level of larval infestation, postemergence sprays of Metarhizium spores integrated without provided better root protection against maggot feeding than spray applications without a cover; rye combined with Metarhizium granules, applied at-planting, had significantly less root scarring compared to corresponding Metarhizium plots without cover crop. The postemergence application of cover cropping resulted in more consistent root injury reductions when combined with granular Metarhizium in 2002, whereas the spray of the fungus at fly oviposition worked better with oat in 2003.
Technical Abstract: This is a report on two years of field trials evaluating Metarhizium anisopliae strain MA1200 with oat or rye cover crops in Pembina County, ND. Oat and rye cover crops were main treatments, sub-level treatments were three seeding rates, 0, 1.5, and 3.0 oat-bushel equivalents per acre and at-planting application of MA1200 granular formulation, a postemergence spray of MA1200 spores, at-planting application of Counter 15G, and an untreated check served as sub-sub-level treatments. Cereal cover crops were broadcast immediately before subarbeet planting. Granular Metarhizium and Counter treatments were applied using modified-in-furrow placement. Metarhizium spray application (2x10E13 infective spores per acre, in 7-inch bands at a spray output volume of 30 gallons/ac) was done at peak fly oviposition. Cover crops were killed by herbicide spray when beets were 7 inches tall. Under a moderate level of larval infestation, postemergence Metarhizium sprays integrated with oat provided better root protection against maggot feeding than without a cover; rye combined with Metarhizium granules allowed significantly less root scarring than Metarhizium without a cover crop. The postemergence application of Metarhizium was successfully integrated with both seed rates of rye. These treatment combinations were superior to no-cover plots. Environmental factors appears to impact the integrated programs because oat cover cropping resulted in more consistent root injury reductions when combined with granular Metarhizium in 2002, whereas the liquid formulation of the fungus worked better without in 2003. Combining planting-time granular and postemergence Metarhizium treatments with either oat or rye enhanced SBRM control.