Submitted to: Journal of Sugarbeet Research
Publication Type: Abstract Only
Publication Acceptance Date: 1/11/1999
Publication Date: N/A
Technical Abstract: The fungus, Metarhizium anisopliae (Metschnikoff), has potential as an alternative to chemical soil insecticides for the management of the sugarbeet root maggot. For 3 years (1996-98) in the same field, soil applications of an isolate of the fungus (ARS-T1) were made over rotations (wheat, barley, and sugarbeets) and seasons (fall and spring) to evaluate the effectiveness of management strategies. There is a need to better understand what happens to the fungus in the soil after applications (i.e., what concentration of conidia is present, do conidia persist throughout the season, does the fungal concentration build-up with repeated applications or timing of applications, and do conidia move within the soil profile). From May 27 to Aug 19 of 1998, soil samples within the top 22.5 cm (in increments of 7.5 cm) of the soil profile were taken every 2 weeks and analyzed for the presence and quantity of conidia. Concentrations of conidia for all the fungal treatments ranged from 40-160 x 103 conidia/g of soil throughout the sampling period. The number of conidia did not increase with more applications, nor did timing of applications (fall vs. spring) affect the levels of conidia present in the soil. 57-89% of the conidia were present in the top 7.5 cm of the soil profile, and there were significantly fewer conidia present in the middle and bottom 7.5 cm of the soil profile when applications were made for only 2 years. The data suggest the fungus persists during the period of maggot activity with no appreciable reduction in conidial concentration, there is minimal buildup of innoculum over the years or with timing of applications, and there is more downward movement of conidia with more years of applications.