Recently, I’ve noticed what look like piles of tiny white droppings on some of the leaves of my lemon tree. On further investigation it became apparent that they were wood shavings which had been dropping out of tiny holes on the underside of the branches and landing on the leaves or ground beneath. Clearly there was a wood borer of some sort inside the branches of the tree, so, under the guidance of Mabel, a local organic farmer whom I buy vegetables from, I cut off a branch and found an oval tunnel right through the middle of the branch. Chopping off bits of the branch, we finally discovered the culprit – an orange grub about an inch long with a dark head. Here’s a rather poor picture of it.
Sorry, it’s such a bad picture, but the others were even worse! Later, I noticed that some holes were filled with tiny ants, which came swarming out when I cut through, but whether they had killed a grub and taken over its tunnel for themselves, or whether they were associated with the grub in some way, I don’t know. Can anybody identify it, and does anyone know of an organic method of removing the creature before my lemon tree dies? At the moment, there appears to be nothing obviously wrong with the tree, but the grub burrows right along the length of branches, which is at the very least going to make them very susceptible to the next typhoon that blows through. Waiting for a natural predator would be the ideal solution, of course, but that would be more likely to happen in a whole, intact ecosystem, whereas my garden, despite having a tremendous array of insects, amphibians, reptiles, birds and assorted soil organisms, is surrounded by wasteland which has been repeatedly disturbed by human activities – currently a flood drainage system is being built nearby. Consequently, the chances of a natural predator arriving like the cavalry over the hill, are pretty remote, I think. What can I do, and how can I stop this happening in future? One possible clue might be the fact that we’ve had an extraordinary number of wasps in the garden this year. Could one of them be responsible?