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Lemon Tree Borer — and how to get rid of it

Adult borer beetleLemon tree borer — a little bug that doesn't live up to its name. The borer doesn't confine itself just to citrus. It could be lurking in any tree, silently killing them.

For this bug item we take you to the dizzying heights of a golden elm, because what we've found here are the clear signs of the bane of most gardeners — lemon tree borer.

To explain the life cycle of the lemon tree borer in the tree is almost impossible. We have to cut a branch to show you the grub — not a good idea in the warmer months of the year. When you cut a branch off a suitable host tree of the lemon tree borer in the warmer months, the adult beetle will lay its new eggs on the cutting wound. That's how you get your infestation.

Borer in branch

By the way, the lemon tree borer's a native of NZ, and it lays eggs in elm trees, citrus trees — you name it. Anything can be affected, as long as the wood is alive.

Now, out of these eggs come little grubs that tunnel into the wood. The grubs grow, and they grow as big as this one. Here's one of the grubs of the lemon tree borer. They go right through the branches and through the stems. They cut themselves that by eating the live wood at the front and excreting loose sawdust at the back. If you do that, sooner or later your excrement catches up with you, so what does the borer grub do? It makes little holes to the outside world and gets rid of all this excrement.

Borer holes in branch

Those holes are actually very handy, because if you can't cut the branches off, you now have access to the main tunnel, via the outside, via their own toilet holes. And that holds the key to organic control of the lemon tree borer.

So, here we're back in our possie, looking at the excrement of the lemon tree borer. I'm going to remove that first. I'm going to get myself a guitar string — I prefer to use a G string, but the B or the A will do — and I'm going to put that into the hole and hopefully spear the little devil into its you-know-what.

Eradicating borer

An alternative way to go is, if you're not so into perverse methods of spearing them is to get yourself a hypodermic needle with kerosene. You can use their toilet hole as access to fill up the main tunnel. It's not too bad for the tree.

When you've done that, get yourself some Blu-Tack and literally clog the hole up. The kerosene fumes will do the killing of the borer grub. See how nicely you can get at the grub without having to saw the branches off, which is not a good idea in summer, because these adult lemon tree borers are on the move. They sniff every cut you make.

The way to go is organic — simple. It doesn't harm the tree, and the borer stops its grinding.

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Last updated: June 2, 2004