Author
Djamila H Djeddour
d.djeddour@cabi.org
CABI
Ascot
Coauthors
Corin Pratt, CABI, Ascot, United Kingdom
Suzy Wood, CABI, Ascot, United Kingdom
Sangay Bhutia, Sikkim University, Gangtok, India
K.J David, ICAR-NBAIR, Bangalore, India
Abstract
Hedychium gardnerianum, also known as wild or Kahili ginger, is native to the Eastern Himalayas and has become highly invasive globally, particularly in New Zealand and Hawaii.
Native range surveys undertaken from 2008-2019 identified several promising natural enemies, including a stem-mining, shoot stunting Chloropid fly (Merochlorops genus). Despite a series of bureaucratic issues affecting the project, several prioritised species were exported and tested in the UK. The flies were consistently collected as single, characteristically “forked” larvae or pupae in individual host stems in the field and hatched in containment but proved difficult to rear; specificity tests also yielded inconsistent results. Published Indian records of Merochlorops are sparse but with an opportunity to examine flies from collected H. gardnerianum stems and their close relatives, a deep taxonomic dive subsequently proposed the presence of three distinct species of fly instead of one, as previously thought. These flies are morphologically very similar and hard to separate without dissection and/or microscopic examination.
A retrospective assessment of the host range testing shed doubt over the purity of cultures used and the inherent differences in susceptibility of test and host plants. Testing biocontrol agents becomes significantly more complex and risky when the taxonomy of the agent is cryptic and the results and implications for this long running project’s progress are highlighted.
keywords
Cryptic species
Chloropid flies
Hedychium gardnerianum
Highlights
Hedychium gardnerianum is host to several damaging and limiting natural enemies in the native range
Distinguishing cryptic species is key to host specificity testing
Maintenance of well curated reference specimens and engagement with systematic experts in country