Irradiation of living plants as an interstate quarantine treatment

Start date: February 2010
End date: September 2010

Andrew Manners, 07 3824 9506
Andrew.Manners@daff.qld.gov.au

To document any phytotoxic (growth inhibiting or poisoning) effects from low-dose gamma irradiation on 20 commonly shipped nursery plants.

If the results show very few to no phytotoxic effects, then irradiation may be a viable option for the quarantine treatment of plants. In this case, the effect of low dose irradiation on three pest groups that pose a serious threat to interstate trade will also be examined.

The project had the potential to open a new avenue of quarantine treatment for living nursery stock, thus facilitating interstate and international trade.

Twenty plant species commonly shipped interstate and internationally were exposed to two levels of irradiation (about 300 and 650 Gy), with a non-irradiated control treatment. Irradiation was conducted at Steritech, an AQIS approved irradiation facility. 

The following plants were tested:

• Agapanthus sp. (blue flowered form)
• Archontophoenix cunninghamiana (Bangalow palm)
• Areca lutescens (golden cane palm)
• Callistemon ´Little John´
• Cordyline baueri ´Red Sensation´
• Dianella caerulea
• Duranta erecta ´Sheena´s Gold´
• Gardenia augusta ´Florida´
• Grevillea ´Superb´
• Harpullia pendula
• Ixora compacta
• Liriope ´Evergreen Giant´
• Magnolia ´Little Gem´
• Melalecua leucadendra (broad leaf  form)
• Murraya exotica
• Philodendron xanadu
• Syzygium ´Cascade´
• Syzygium paniculata ´Elite´
• Tibouchina ´Jazzie´
• Waterhousia unipunctata

The growth rate, chlorophyll content and plant condition were measured fortnightly for 16 weeks post irradiation. The above ground dry weights of plants were measured before irradiation (a subset that was then discarded from the trial) and 16 weeks after irradiation.

All species of plants were negatively affected by low and high gamma irradiation. The only plant (Liriope ´Evergreen Giant´) that appeared free of phytotoxic effects was not able to reshoot after harvesting above ground biomass, whereas non-irradiated plants reshot vigorously. The degree to which plant species were negatively affected and the time frames in which phytotoxic symptoms were observed varied across species.

More experimental results

Conclusion

Irradiation of living plants at doses exceeding about 300 Gy was not feasible as a quarantine treatment.

• Andrew Manners, Senior Entomologist
• Brock Dembowski, Technical Officer
• Dana Ashford, Field Assistant

This project was funded by the Nursery and Garden Industry Australia (NGIA). Nursery and Garden Industry Australia has funding for further research to prioritise non-chemical alternative treatments that could be used for interstate quarantine e.g. modified and control atmosphere techniques.

Irradiation conducted at Steritech, Narangba, Queensland
Research conducted at Redlands Research Facility, Cleveland, Queensland

Andrew Manners
Ph 07 3824 9506
Email: Andrew.Manners@daff.qld.gov.au