OLIVE groves in the Ovens Valley are being attacked by a fast-spreading pest, reportedly the worst infestation in years, impacting the local olive crop and adding costs for growers.
Growers are reporting an unexpected proliferation of the olive lace bug, a sap-sucking insect up to 3mm in size, attacking the leaves and causing mass defoliation if left untreated.
At Micheal Freudenstein’s Rosewhite property some olive trees appear completely leafless from the sap-sucker.
“We've never had them before,” he said.
“Healthy trees should withstand a fair bit of disease pressure but this has just overwhelmed many groves,” he said.
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Mr Freudenstein said nearly half of his 1000 olive trees have been impacted by the insect, leading to an estimated 75 per cent cut in his crop this year.
He will be consulting with an arborist to prune the particularly impacted trees to encourage regrowth.
“It's an expensive operation, the spray you have to use is three or four hundred dollars for 20 litres,” he said.
“We've never had to spray for anything in 20 years.”
He said nearly every olive grower he has spoken to has been impacted – even his neighbour with one tree.
“He asked me what the problem with the tree was and I had a look and there were lace bugs all over it,” he said.
Whorouly-based olive grower Tony LaSpina said he’s never seen a lace bug infestation in the area before, with every tree in his 3000-strong grove impacted by the insect.
“Usually olive trees don't get anything go wrong with them, but this year they have,” he said.
“It’s impacted a lot of trees, I think, around the area.”
He said they won’t have an olive harvest this year due to the lace bug, when they usually harvest 18-20 tons of the fruit.
According to former olive grower Colin Bertuch, lace bugs can be treated with sprayed pesticides, such as a pyrethroid or oil combined with a surfactant – but it’s best to get them early.
He said the Australian native insects will start breeding from September and are probably into their third or fourth breeding cycle by now.
“You can use olive oil in a simple form with a surfactant and spray them, and they suffocate the nymphs at a certain period in their cycle,” he said.
He continues to work on local groves and said he’s never seen infestations this bad.
“There are not many groves that have no impact,” he said.
“Where there is no impact, or apparently no impact, I would suggest the owners have sprayed fairly early in the piece and kept them under control.”
He said a completely defoliated tree will take around three years to restore its full canopy, impacting fruit production.
“Once your leaves are all impacted, you no longer have photosynthesis and carbon deposits going into your fruit,” he said.
Russ Knight, from the Goulburn Strathbogie Olive Growers Association, said the pest can be eradicated if treated properly when the insects are still wingless ‘instars’ (between nymphs and adults).
“That's when you belt them,” he said.
“Once they're in the fourth or fifth instar stage they've developed wings - they're gone.
“They will fly off right around the grove and you are in deep trouble.”
