Pear and Cherry Slug Control

Fruit, Pests & Diseases, Summer

December 19, 2011


Pear and Cherry Slugs

Pear and Cherry Slugs

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.

Pear and Cherry Slug Control using woodash

Pear and Cherry Slug Control using woodash

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?

12 Responses to “Pear and Cherry Slug Control”

  1. Paul says:

    Thanks for the info on pear slugs! I plan to use the ash dusting method in the spring. In the meantime, I have also learned that a vigorous washing of younger, smaller trees, with a garden hose once a week is also an effective method to remove the buggers. I plan to do both … Dusting on Friday, Washing on Monday? Anyway, the slugs are a bloody nuisance and have decidedly reduced our fruit crop this year. They have to go!

  2. Matt says:

    Good luck. Let me know how you get on using the combo.

  3. Claud says:

    Thank you for the site & the info. We have been at this Mallee property 3 years. First year at the tail end of the drought we had 6- 8 pears on the old pear tree. Second year after the drought broke we had a bumper harvest & no problems Third year had a huge infestation on our old pear tree (last year) with almost no fruit. Tried all sorts of remedies, talcum powder on leaves, dishwashing liquid mixed with something else, all with no effect until I mixed up the dishwashing detergent at about 4x the recommended strength. But all the leaves dropped off as well as the slugs. This year there is lush leaf growth but only 9 -10 pears, & suddenly this week I see the dreaded slugs arriving on a few leaves. Now to try builders lime mix or wood ash as seen on your site. Did my dishwashing mix hurt the tree so that it didn’t have the strength to produce much fruit??
    Cheers Claud.

  4. Matt says:

    Hi Claud, thanks for your comment. I would say that your detergent didn’t weaken the tree, it was probably the stress of dealing with the slugs that did it. Maybe your detergent mix saved it!

    I have found this year I needed to do the wood ash twice within a week, but since then the tree has been pretty free of slugs. I imagine it will need another few dowsings with the ash throughout the summer yet.

    Good luck with your tree and I hope you get a bumper crop next year.



  5. lesley says:

    hello, i have been using pyrethrum spray with good effect, but the cost was too high, so i found that almost any of the small daisy family will work. chamomile tea cost about 36 cents to make a liter… just make a strong tea with 5 tea bags to a liter, i open up the bags then filter the tea thru a petrol funnel with a sieve , then add a small amount of dishwash liquid. seaside daisy and feverfew also works well…any of the daisies in your garden will work but i am trying to only use daisies that are also medicinal as i usually spray it on myself at some point. i also spray the cabbages and broccoli to kill the young grubs….good luck out there..

  6. Matt says:

    Thanks Lesley, that is a REALLY good tip. Cheers, Matt

  7. nicola says:

    Thanks for the quick ID. Now I am off to seriously ‘deter’ the little beasts. Just needed to confirm they were not aliens first.

  8. Jade says:

    Hi, I was just wondering if I have a cherry slug problem. I have an cherry tree right next to my fish pond and I keep seeing like saw dust on the water. Could this be some kind of insect? I have a picture of it but I don’t know how to add it to my comment.

  9. Scott says:

    I also saw another option which has worked will for me – simply dusting with flour – which apparently dries out the skin of the slug and causes them to drop off or die – seems to have worked well

  10. Matt says:

    Hi Jade, not sure about that one. It’s unlikely to be cherry slug I would have thought. You’ll often first notice cherry slug through the damage it does to the leaves.

  11. sabine says:

    I noticed the pear trees (planted as bare root in August last year and it’s early Feb now) though having grown well were showing signs of disease. Google led me to your site and having read the tips I quickly checked the wood heater for ash. Thankfully there is some left from the last fire so I dusted both the trees and will do so until they seem better. I wonder if any of the little blighters have dropped off as pupae yet. Well at least I know what to do.

  12. Kirby says:

    Claud- Using too much soap for a soap spray can be phototoxic for the leaves, and would hurt the tree…

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