The Epiblema Dilemma: Challenges for its use as a biological control agent for parthenium in Africa Andrew McConnachie* & Lorraine Strathie (ARC-PPRI, Cedara, South Africa) Parthenium hysterophorus Weed of international significance introduced to 30 countries throughout the world (Shabbir 2012) Parthenium hysterophorus Current global control strategies: Chemical Mechanical Other (containment, competitive species, etc.) Biological Strategies in SA: Chemical Biological Zygogramma bicolorata Listronotus setosipennis Smicronyx lutulentus Epiblema strenuana Puccinia abrupta var. partheniicola (Winter rust) Carmenta sp. nr ithacae Puccinia xanthii var. parthenii- hysterophorae (Summer rust) Epiblema strenuana (Tortricidae) Origin: Widely distributed over North & Central America (Canada in north to Mexico in the south; California in west to eastern seaboard of the USA) Mode of action: Stem-galler (stems & growing points) Impact: Significant - plant height and flowering (Dhileepan 2003) Most damaging and widespread agent in Australia at present Epiblema strenuana Field host range (native range): Canada: Xanthium commune USA: P. hysterophorus, X. trifida, X. artemisiifolia, X. psilostachya Mexico & Caribbean: P. hysterophorus Laboratory host range: Mexico: P. hysterophorus, P. confertum, Ambrosia psilostachya, Rudbeckia sp., Bidens pilosa Australia: P. hysterophorus, Ambrosia artemisifolia, X.strumarium India: P. hysterophorus, Guizotia abyssinica Guizotia abyssinica (noog, niger seed, blackseed) The dilemma Epiblema is very damaging & widespread in Australia Epiblema will rapidly disperse northwards in Africa based on Australian evidence Guizotia not an issue for SA, but of important consideration for Ethiopia SA legally obliged to only inform SADC members of releases Polyphagous in native range Future pressure from SA roleplayers to further test and consider Epiblema Epiblema strenuana Field host range (native range): Canada: Xanthium commune USA: P. hysterophorus, X. trifida, X. artemisiifolia, X. psilostachya Mexico & Caribbean: P. hysterophorus Laboratory host range: Mexico: P. hysterophorus, P. confertum, Ambrosia psilostachya, Rudbeckia sp., Bidens pilosa Australia: P. hysterophorus, Ambrosia artemisifolia, X.strumarium India: P. hysterophorus, Guizotia abyssinica Imported to SA (2010) Initial strategy: Test host range of agent on the main varieties of G. abyssinica grown in East Africa Guizotia abyssinica Five main varieties of G. abyssinica grown in Ethiopia (Kuyu, Shambu, Ginchi-1, Fogera & Esete) Parthenium hysterophorus Noog growing areas (mid- to high altitude) No-choice trials Subfamily Tribe Species (cultivar)nMean tunnelling score ( SE) a, b Mean number of galls ( SE) b Mean number of larvae ( SE) b Mean number of adults ( SE) bAsteroideae HeliantheaeParthenium hysterophorous32.67 (0.33)8.33 (4.06)2.33 (1.86)5.00 (2.52) HeliantheaeGuizotia abyssinica (Ginchi-1)33.00 (0.00)7.67 (2.03)1.67 (0.88)1.00 (1.00) HeliantheaeG. abyssinica (Esete)32.67 (0.33)5.33 (2.03)1.50 (0.50)0* HeliantheaeG. abyssinica (Fogera)32.67 (0.33)5.00 (2.52)0.67 (0.67)0* HeliantheaeG. abyssinica (Shambu)33.00 (0.00)5.67 (1.67)0.67 (0.67)0* HeliantheaeG. abyssinica (Kuyu)33.00 (0.00)3.67 (1.86)0.67 (0.33)0* a Tunnelling scores were assessed as follows: 0 no tunnelling; 1 1-30% stem tunnelled; 2 31-60% stem tunnelled; 3 % stem tunnelled. b Within the same column, asterisks following the mean (SE) indicate a significant difference (p < 0.05) between the control and the test species; Mann-Whitney U test. Tests conducted in gauze covered cages 5 pairs of one-day old adults per cage Duration: 15 days Plants held in cages for 8 weeks (eclosion ceased) Dissected & assessed Epiblema damage Multiple-choice trials Tests conducted in walk-in cage (5x3x2m) 10 pairs of one-day old adults Duration: 15 days (5 day rotation to compensate for effect of light) Plants held separately in cages for 8 weeks (eclosion ceased) Dissected & assessed Multiple-choice trials Tests conducted in walk-in cage (5x3x2m) 10 pairs of one-day old adults Duration: 15 days (5 day rotation to compensate for effect of light) Plants held separately in cages for 8 weeks (eclosion ceased) Dissected & assessed Subfamily Tribe Test plant speciesnMean tunnelling score ( SE) a,b Mean number of galls ( SE) b Mean number of larvae ( SE) b Mean number of adults ( SE) bAsteroideae HeliantheaeParthenium hysterophorous92.56 (0.33)6.33 (4.33)13.33 (5.49)2.44 (1.45) HeliantheaeGuizotia abyssinica ( (Ginchi-1)60.17 (0.33)*0*0.17 (0.33)*0* HeliantheaeG. abyssinica (Esete)60.33 (0.333)*0.17 (0.33)*0.67 (0.67)*0* HeliantheaeG. abyssinica (Fogera)60* HeliantheaeG. abyssinica (Shambu)90.5 (0.33)*0.33 (0.33)*0.5 (0.33)*0* HeliantheaeG. abyssinica (Kuyu)90.11 (0.00)* 0* HeliantheaeXanthium strumarium31.50 (0.50)4.50 (2.50)5.50 (4.50)2.50 (0.50) a Tunnelling scores were assessed as follows: 0 no tunnelling; 1 1-30% stem tunnelled; 2 31-60% stem tunnelled; 3 % stem tunnelled. b Within the same column, asterisks following the mean (SE) indicate a significant difference (p < 0.05) between the control and the test species; Mann-Whitney U test. Larval development trials Subfamily Tribe Species (cultivar)nFeeding damage (frass) Gall formationEclosionTotal developmental time (days SE)Asteroideae HeliantheaeParthenium hysterophorous6 YesYes (6/6)Yes (4/4)40.8 (2.1) HeliantheaeGuizotia abyssinica (Ginchi-1)6 YesYes (3/6)Yes (1/6)47* HeliantheaeG. abyssinica (Esete)6 YesYes (2/6)Yes (3/6)46.7 (1.5)* HeliantheaeG. abyssinica (Fogera)6 YesYes (3/6)Yes (2/6)48.5 (1.5)* HeliantheaeG. abyssinica (Shambu)6 YesYes (2/6)Yes (1/6)49* HeliantheaeG. abyssinica (Kuyu)6 YesYes (3/6)Yes (4/6)53 (3.4)* Within the same column, asterisks following the mean (SE) indicate a significant difference (p < 0.05) between the control and the test species; Mann- Whitney U test. Tests conducted in gauze covered cages Eggs incubated & placed singly on plants Plants held separately in cages until adults eclosed Summary No-choice: E. strenuana feeding damage (larval tunnelling & galling) & larval counts on G. abyssinica not significantly different to P. hysterophorus No adults eclosed from 4 cultivars of G. abyssinica, possibly due to insufficient stem tissue to complete development Multiple choice: Significantly less E.strenuana feeding damage & larval counts on G. abyssinica cultivars Lack of adult eclosion on G. abyssinica again possibly due to insufficient stem tissue to complete development Larval development: Variable gall formation and eclosion of E. strenuana on G. abyssinica cultivars Significantly longer developmental times on G. abyssinica cultivars Conclusions Decision at SA national weed biocontrol workshop (2012): Shelve agent Compile a risk analysis & publish Reassess after all other agents have established & been assessed Further information: Competitive interactions with other agents? Conduct open field host range trials (Israel or Australia) Acceptable levels of damage to noog in Ethiopia? Use of pesticides? Acknowledgements Staff: Sakhi Sambo, Milly Gareeb, Derrick Nkala, Samora Mqolombeni, Lynette Khumalo Funders: DEA (Natural Resource Management Programmes), KZN DAEA