Buddleia leaf weevil in New Zealand 5yrs on Michelle Watson

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

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

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

Buddleia in forestry 1 yr old stand

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

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

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 mm adult weevillarvaepupa

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

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

 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 What we found?

Other release sites  Further releases made in areas where buddleia a pest  Councils, forestry, gold mine  ~ 40 releases  weevils per release

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

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

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

Buddleia with agent Researching ability to colonise seedlings

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

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

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 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 Implications for forestry

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

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?

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

 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 Big thanks to…

Implications for forestry  C. japonicus will 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 ?