Buddleia leaf weevil in New Zealand 5yrs on

1. Buddleia leaf weevil in New Zealand 5yrs on Michelle Watson

2. Overview Overview: • The weed • buddleia in forestry • Buddleia in native forests • biocontrol in forestry • The insect • Field releases • what we found • implications for forestry • Another biocontrol agent? • How to collect and redistribute the agent

3. Buddleia (Buddleja davidii) • Woody shrub from China • Rapidly colonises disturbed sites • Fine, wind-dispersed seed • Able to flower 1st yr, attain 4m in 2 yrs! • Weed of plantation forests and natural areas buddleia flower

4. Buddleia in forestry • Reduces growth of plantation species • Number 1 weed central Nth Is. • Difficult to control with chemicals • Cost forestry industry ~$2.9 million/yr control & lost production • Buddleia control vital 3-5yrs after planting

5. Buddleia in forestry 1 yr old stand

6. Buddleia in native forests • Colonises disturbed sites = stream beds & slip sites • Alters plant communities, blocks access, shades rivers • e.g. Te Urewera, Kaikoura • Difficult to control due limited access

7. Buddleia biocontrol in forestry • Currently use herbicides to control buddleia • But need to reduce chemical use (eg.FSC) Challenge of an integrated control method: • Must impact buddleia within 3 years of planting • Weeds must be kept less than 60% crop height • Large areas of buddleia need to be controlled • Agent must be highly mobile to locate new sites

8. Buddleia leaf weevil (Cleopus japonicus) • Leaf feeding weevil from China • Larvae most damaging stage • Weevils lay 1-20 eggs per day • Weevils readily fly • First released in NZ in spring 2006 4mm adult weevil larvae pupa

9. Field releases • 1000 weevils released at 5 sites spring 2006 • Tracked dispersal, damage and agent numbers

10. What we found? • Established at all release sites • Adults stop mating & laying eggs at high temps • no larvae January • Indicates do best moderate winter & summer February 2007 March 2008

11. What we found? • Larvae present Sept to late May/early June • Up to 95% defoliation in April 2008,’09, ’10 and ‘11 • Heavy defoliation seen up to 5km from releases

12. Other release sites • Further releases made • in areas where buddleia a pest • Councils, forestry, gold mine • 2007-2011 ~ 40 releases • 200-500 weevils per release

13. Distribution • Established at all release sites • Most new location records in Bay of Plenty • Dispersed over 50km from some release sites • Still lots of sites not colonised by weevil, would benefit from being spread by you *

14. What we know about the agent: • Able heavily defoliate buddleia • Defoliation peaks in autumn • Repeated defoliation • Able to locate host plants further away - good adult flight ability

15. What we know about the agent: • Microclimate • Preference for gullies • Sunny, open areas • Often exhaust their resource – new adults forced to seek new host plants to survive winter • BUT, don’t know whether will colonise newly planted forests quickly enough, and impact

16. Buddleia with agent Researching ability to colonise seedlings

17. Number larvae correlated with damage y = 10.62 x 0.33 R2 of 0.810 *Treatment level averages, by distance, for all days after release.

18. Buddleia height is reduced End year 1= sig reduction in growth compared to insecticide-treated (control) plants Values - least square means & standard errors Treated plants Untreated plants

19. Implications for forestry Agent damage • Known that > 30% defoliation needed to effectively suppress buddleia in forestry • Created a model of feeding damage with distance • Predict that by end Year 1= plants at distance 0 will be more than 30% defoliated

20. Implications for forestry What does this all mean? • Results indicate C. japonicus has the ability to suppress growth of buddleia seedlings • At first this is close to the source population • Repeated defoliation between & within yrs can be expected

21. Implications for buddleia biocontrol • Buddleia has amazing ability to re-grow following defoliation • At first responds by re-growing larger leaves • Repeated defoliation needed to deplete plants reserves • Plant reserves depleted after second year defoliation • = fewer flowers, less foliage, less height growth

22. Complimentary agent? Is another agent needed? • Mecysolobus erro = stem boring weevil • Causes stems to wilt and die • More host-testing needed • Difficult to re-collect and rear • May attack spring growth when cleopus is less effective?

23. Help spread this agent • Adults most robust life stage • Best collected in spring and autumn when easy to find • Collect by beating buddleia whilst holding a beat sheet, tarp, or upside-down umbrella underneath • Keep adults out of the sun in a ventilated container with buddleia stems • Release ~20-50 adults on a clump of plants • Contact Scion for advice on collection sites

24. Big thanks to… • Funding by FRST & Better Border Biosecurity (B3) program • Forestry companies: • Rayonier, Hancock F.M., Timberlands, Pan Pac, Lake Taupo Forest Trust /NZ Forest Managers, Tempest & Associates Forestry, PF Olsen, et al. • The Conservation Company • Jenny Dymock, Des Pooley • Other forestry companies and Councils with releases • Royal Society of NZ • Scion Forest Protection group

25. Implications for forestry • C. japonicuswill only be an economically successful buddleia control option in forestry if: • disperses rapidly • reduces growth of buddleia over entire stands • effective within the first 3-5 yrs • However, benefits from buddleia control > 3yrs • easier for pruning & thinning • roadside buddleia less vigorous • reduced seed production ?