BBQ photo reveals invasive pest taking over Aussie gardens 'quickly and easily'
An Aussie gardener helped his neighbour prune the infested lemon tree before the problem got out of hand.
As the warmer weather nears, Aussies may be bringing out their barbeques for an outdoor feed. But it was for an unlikely reason one man prepared a "nice barbie" in his backyard last weekend.
An image shared by the West Australian gardener shows his BBQ covered in off-cuts from his neighbour's lemon tree, which he helped prune. All because it housed an invasive, serial pest that "spreads very quickly and easily" – and burning them is one way to get rid of the pest.
To most, the tree branches might appear harmless, with bulbs appearing to grow within the stems. But the unusual-shaped bark is a sign of a citrus gall wasp infestation which targets citrus trees, mostly lemon and grapefruit, and can wreak havoc on the production of the fruit, and its trees.
"The citrus gall wasp is a native insect to Australia found on finger limes. Now, these wasps happily attack other citrus trees like oranges and lemons," Professor Brett Summerell, Chief Scientist at Botanic Gardens of Sydney told Yahoo.
"These wasps can reduce fruit production and can make citrus trees quite sick."
How to manage a citrus gall wasp infestation
The gardener shared the images on Facebook this week explaining he's helped his neighbour prune the tree which was infected. "Nice weather for a BBQ. Helped neighbour prune lemon tree badly infested by citrus gall wasp. The galls are pruned out for a nice barbie," he said.
Pruning is said to be a suitable control method, and one homeowners can undertake easily. However, wasps can still emerge from offcuts if pruned too close to their usual emergence period — usually between September and December. So burning can be one way to mitigate any risk associated with wasp-infected offcuts. Shredding and mulching or placing the branches in a sealed bag can help too.
The best time to prune out galls is from April to June.
Serious damage caused to citrus trees
The Citrus gall wasp is an Australian native insect originally from northern NSW and Queensland but is now established in most Perth suburbs after spreading across the country.
It was first detected in WA in the Perth suburb of Eden Hill in 2013 and is now an established pest in the Perth metropolitan area. South Australia and Victoria have also been impacted.
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The insect is known to target all citrus species and is considered an ongoing pest for gardeners. Thankfully, it has not been found in commercial citrus orchards in Western Australia yet, according to the state's Department of Primary Industries and Regional Development — but can still be problematic.
The eggs are laid in new shoots of citrus trees, as shown in the images, and the tree reacts by producing distinctive galls around the developing larvae. Adult wasps then emerge from galls.
The galls created to house the larvae are known to disrupt water and nutrient flow which can weaken trees and affect productivity. Heavy infestations will often reduce fruit size and quantity over time.
"Instead of just pruning your tree, it is recommended to carefully slice the top of the gall so the wasp larvae are exposed and die. You can also remove them from your plant by pruning the affected parts, the galls, but if you do this, you should dispose of it in a sealed bag so they cannot emerge later," Summerell said.
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