| This study evaluated the effectiveness of combining an insect-pathogenic fungus, Metarhizium anisopliae var. anisopliae (Metch.) Sorok., with either oat, Avena sativa L., or rye, Secale cereale L., cover crops to control the sugarbeet root maggot (SBRM), Tetanops myopaeformis (Roder). Oat was sown at 0, 186, and 233 seeds/m2, and rye was sown at 0, 374, and 466 seeds/m2. The fungus was applied either as granular formulation at planting or as postemergence spray close to peak fly activity. Test parameters in this study were root injury ratings, root yield, and sucrose yield.; Cover crop seeding rate had a significant impact on all test parameters, and insecticidal treatments had a significant impact on yield parameters only. The root injury in check plots ranged from 5.5-7.1, indicating a high SBRM pressure. Plots that received the insect pathogen in the absence of ground cover had high levels of root injury (root injury rating ≥5.5 on a 0-9 scale), which resulted in low root and sucrose yields. A combination involving a high seeding rate of rye with M. anisopliae spray resulted in the lowest root scarring (4.5) and high yields (46.2 Mg/ha root yield and 4.6 Mg/ha sucrose yield). Oat combined with M. anisopliae provided inconsistent results. Plots seeded to a high seeding rate of oat had an overall root injury of 5.0 and produced 43.4 Mg/ha root yield. A high seed rate of cover crops, although beneficial for SBRM control, removed more soil moisture compared to the low rate.; Formulation type significantly impacted conidia survival. Cover crops did not affect M. anisopliae persistence in this experiment. More conidia were found after 30 d in plots that received the sprayable liquid formulation than those treated with granules.; The pathogenic fungus, Fusarium solani (Mart.) Sacc., was isolated from T. myopaeformis pupae during a field survey. About 44% pupae (n=1200) collected were found infected from F. solani. This fungus successfully penetrated the sclerotized pupal cuticle and caused rapid tissue destruction in freshly-pupated individuals. Adults often formed inside older pupae, but died when exposed to this pathogen. The LC50 of F. solani was 1.8 x 106 conidia/ml. |
