Grower-Adoptable Formulations of the Entomopathogenic FungusMetarhizium anisopliae(Ascomycota: Hypocreales) for Sugarbeet Root Maggot (Diptera: Ulidiidae) Management

Abstract

Producers in many North American sugarbeet (Beta vulgaris L.) growing areas rely heavily on organophosphate insecticides to manage the sugarbeet root maggot, Tetanops myopaeformis Röder. The threat of losing organophosphate options because of the potential for development of resistant root maggot strains or regulatory action has prompted a search for alternative control tools. American Type Culture Collection (ATCC) accession no. 62176, a strain of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin, was studied in field trials as a bioinsecticidal option for control of T. myopaeformis larvae because of shown virulence in preliminary laboratory testing. The fungus was evaluated at four field sites during 2001 and 2002 as a planting-time granule, an aqueous postemergence spray, or a combination of both. Three rates of M. anisopliae conidia, 4 × 1012 (1×), 8 × 1012 (2×), and 1.6 × 1013/ha (4×) were applied as granules, and the spray was tested at the 1× rate. A significant linear response in sucrose yield in relation to M. anisopliae granule application rate confirmed its entomopathogenic capacity under field conditions. Each multiple of M. anisopliae granules applied affected a yield increase of ≈171 kg sucrose/ha. The fungus was less effective than conventional insecticides at preventing stand loss from high root maggot infestations early in the season. It is concluded that, with additional research, mycoinsecticides could potentially be incorporated into management systems to complement chemical control tactics such as insecticidal seed treatments, soil insecticides (possibly at reduced rates), or postemergence materials for integrated control of T. myopaeformis adults or larvae.