* Commercial macadamia orchards across Australia infected with native mistletoes

* Senior CSU ecologist called in to assist in developing better control strategies

* Current management techniques and varieties add to problem

Grown for its high value, moreish nuts, commercial macadamia orchards stretch from Mid-North Coast NSW to Central Queensland.

However, this native tree is under siege from a native parasite, the mistletoe, and a Charles Sturt University (CSU) expert in mistletoes was asked to provide advice on its control in commercial orchards.

Professor David Watson, an ecologist and international authority on mistletoes with the CSU Institute for Land, Water and Society, recently completed a survey of mistletoes that infect macadamias.

He presented his findings at a national grower meeting held in Bundaberg, Queensland, in December 2018, where he suggested various control and management techniques for mistletoe, which are spread by birds that prefer mistletoe fruit (pictured below).

“Unfortunately, the mistletoe is well adapted to infecting many of the popular commercial varieties which have more open, well-lit canopies which mistletoes love,” Professor Watson said.

“Tree management that trims the crown and removes inner branches also encourages mistletoes to establish.”

Professor Watson  believes the most effective way to control mistletoe is to apply principles from integrated pest management.

“Monitoring orchards regularly for infection, regularly removing mistletoe branches twice a year, and adjacent growers work together to stop outbreaks can all help manage mistletoes in orchard areas.

“It has to be a joint effort by all who work in an orchard.”

Professor Watson (pictured left) has also recommended that more research could also help fine-tune management practices.

“We need to know more about infection rates in different macadamia varieties in all growing regions and growing conditions. The use of thermal imaging via drones could help detect the extent of mistletoes across a macadamia orchard.

“Chemical control of mistletoes has been trialed in many forestry and plantation settings, but with mixed results. In addition, bird control such as lasers could deter mistletoes dispersers from orchard of used across the growing area, but this needs to be tested.

“Finally, we need to find out if mistletoes are also harbouring beneficial insects that may control mistletoes, suppress other insect pests or increase macadamia pollination. This may affect our management decisions.”

Professor Watson is excited to be involved in this type of research in regional Australia.

“This is an example of where native ecology meets commercial agriculture, and both bring issues that need to be addressed as part of a complex interaction that includes man and nature,” he said.