Pear and cherry slug is a common problem in my area, mainly due to the fact that this was a fruit growing area of Melbourne which has left the area with an endemic problem of fruit tree pests. Pear and cherry slug control is a task that I have grappled with ever since I put my cherry tree in a few years ago.
Initially I wasn’t familiar with the problem but as the leaves on my cherry tree were gradually reduced to skeletons I knew that I had an issue. A bit of research revealed that it was pear and cherry slug and I quickly deduced that some sort of control was going to be necessary. A quick spray with pyrethrum spray seemed to sort the devils out.
The pear and cherry slug is the larvae of the sawfly. The adult sawfly lay their eggs on the leaves of the cherry or pear tree which then hatch to for the slugs. The slugs proceed to eat the leaves of the tree, producing the distinctive lace like pattern that is indicative of the problem. On a closer look you will see the small black slugs on the leaf.
Once the slug has reached maturity it will drop to the ground and pupate. After it completes that process it will emerge to fly back up to the leaves of the tree to lay its eggs. There are two lifecycles a season, so that is why pear and cherry slug control is important, otherwise the second, heavier wave can really decimate an already weakened tree.
Other Pear and Cherry Slug Control Options.
Now I don’t really like using pyrethrum spray if I can help it as it is pretty non-selective, killing both the beneficial insects as well as the pests, and in an organic garden the beneficial insects are quite important. That is why I started looking for other methods of pear and cherry tree slug control. The best one that I tried this year was simply casting wood ash onto the tree (from downwind). I have seen a couple of theories as to how this works including that the ash changes the pH of the leaf, killing the slug. Having seen it in action I think that it is more that the dry ash simply dehydrates the slug, killing it. Of course the ash has the added benefit that it is high in potash which is essential for good fruit production, so you are fertilising the tree at the same time.
I have also seen suggested using a lime spray on the leaves to kill the slugs. This is also supposed to change the pH which sounds very plausible, though I guess this will dehydrate the slugs too. Peter Cundall describes how to use this method in his article here, though he does seem to mix up industrial quantities, so adjust the proportions for your needs. Regardless of the method you use, you do need to control this pest as it will quickly eat through all of the leaves, seriously weakening the tree and reducing your cherry and pear crop for next year.
So let me know using the comments section below, have you had any luck with pear and cherry slug control using these methods? Or do you have another method that has worked well for you?