Submitted to: Sugarbeet Research and Extension Reports
Publication Type: Proceedings
Publication Acceptance Date: January 13, 1998
Publication Date: N/A
Interpretive Summary: The term "biological control" has been used, at times, in a broad context to encompass a full spectrum of biological organisms and biologically based products including pheromones, resistant plant varieties, and autocidal techniques such as sterile insects. The historical and more prevalent use of this term is restricted to use of natural enemies to manage populations of pest organisms. Biological control has been spectacularly successful in many instances, with a number of pest problems permanently resolved by importation and successful establishment of natural enemies. On the other hand, this approach has met with limited success for major pests of row crops or other ephemeral systems. The problem is often not the lack of effective natural enemies but management practices and a lack of concerted research on factors that determine the success or failure of importation attempts in the specific agro-ecosystems. Pathogenic fungi are of special interest for a number of reasons. They are often the only known natural pathogens of certain pests. Impressive epizootics of insects are commonly observed, in which entire insect populations are killed by fungi. Fungal pathogens attack insects directly by breaching the host integument, assisted or enabled by cuticle-degrading enzymes. Bacteria and viruses are by comparison passive invaders; insects must directly ingest these agents, or they enter through wounds or natural openings. Our results from the Laboratory and greenhouse demonstrate the ARS T-1 strain of our pathogenic fungus is very effective in killing all developmental stages of the sugarbeet root maggot.
Technical Abstract: Our previous laboratory studies have shown the efficacy of the entomopathogenic fungi Metharhizium anisopliae (ARS T-1 strain) on first and third instar sugarbeet root maggots (SBRM). Mortality at the most damaging 3rd instar stage was over 90% fourteen days after exposure. The fungi are also effective against adult flies. Six days after inoculation, mortality rates were 100% for M. anisopliae treated adult flies. In field tests conducted in 1996 and 1997, the best biocontrol using M. anisopliae (ARS T-1 strain) was compared to Lorsban and untreated controls for recoverable sugar. The best biocontrol treatments always involved spring and fall application of ARS T-1. As can be noted, the ARS T-1 treatment equaled Lorsban in 1996 and significantly exceeded it in 1997. This treatment exceeded the Lorsban chemical control by 400 pounds and the untreated control by 1400 pounds of recoverable sugar per acre.