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Isolation and development of effective fungal biocontrol for elongate hemlock scaleĀ 

Elongate hemlock scale (EHS) completes its life cycle on the underside of needles of primarily fir and hemlock. This insect threatens Christmas tree production in the Eastern United States by impacting tree health, aesthetic value and exportability. These characteristics are paramount for a salable Christmas tree, and so this very small insect (~2 mm long) is a large concern for growers. Unfortunately, EHS may evolve to resist chemical pesticides. Moreover, these pesticides can also kill insects that are In our Christmas Tree Promotion Board (CTPB) funded project, we sought to identify fungi that naturally infect and control EHS in Christmas tree operations. After scouting in Ashe County North Carolina in 2020, an insect-killing fungus with a high degree of specificity was natural enemies of EHS, which can ultimately worsen EHS infestations found to be present across multiple Christmas tree orchards. Multiple strains of this fungus were isolated in the lab and identified as Conoideocrella luteorostrata (Figure 1A). This fungus kills armored scale insects, including EHS, in its native range in southeastern Asia. Importantly, the narrow host range of this fungus suggests that it would not infect natural enemies of EHS. Our work revealed that the same fungus is naturally causing outbreaks of disease (killing immature EHS) in North Carolina. We sought to further characterize this fungus to ultimately develop methods to apply this fungus directly to Christmas trees to control EHS. Other fungi, such as Colletotrichum fioriniae and Metarhiziopsis microspora, have been developed for this purpose; however, the potential application of these fungi is complicated by their ability to live within needles or infect other plants. We sought to isolate CL from within the needles of sampled Christmas trees, including those with EHS cadavers colonized with CL, to see if CL adopted a similar lifestyle within plant tissue. These experiments revealed that CL is naturally limited to EHS in Christmas tree operations. This is an ideal characteristic for a potential biocontrol agent. During our project, we have worked to develop bioassays to challenge EHS with CL and observe the infection process. This will allow us to evaluate the efficacy of this fungus for development into a commercial biopesticide.

  • Project ID20-10-WVU
  • CategoriesInsect Management
  • Growing Region(s)Mid-Atlantic
  • Tree SpeciesFir
  • Investigator(s)Kasson
  • Institution(s)West Virginia University Division of Plant and Soil Sciences
  • Research Year2020
  • Publication Year2020
  • ReportDownload 📁