Breeding insect resistant trees
From the Winter 2007 edition of Bush Telegraph Magazine.
A little creature that feeds on the leaves of eucalyptus trees, particularly the flooded gum, causes a wave of fear every autumn.
People on the New South Wales north coast who live near large stands of flooded gum (Eucalyptus grandis) see the leaves turning brown nearly every autumn and think they are dying.
The culprit is Cardiaspina fiscella, a tiny insect which creates a yellow-brown, lacy or fan-like cover on the lower leaf surface.
“This occurs mostly on mature foliage, with several appearing on each leaf,” said Forests NSW tree improvement manager, Michael Henson.
“Psyllid nymphs can often be seen under these formations, or lerps, as they are called.”
The psyllids can kill the leaf, which turns yellow then red. Leaves on heavily affected trees can appear purple or brown.
But two trees near Woolgoolga have shown some resistance to the insect attack over recent years, so much so that Forests NSW has collected small branch material and grafted it in an effort to observe how resistant the two trees are.
“The specimens collected were grafted onto seedling rootstocks in order to capture the germplasm,” Michael said.
“The captured germplasm will be DNA tested and used in our tree breeding program, and may be used as a potential source for production of hybrids.”
Public Affairs & Media, Coffs Harbour
