Ooey-gooey Pear Slug

Pest pear slug

So, there I am, wandering about my garden, wondering what I’m going to start the fall season off with in the way of an article.  It’s a little early for bulbs, too late for annuals, perennials have had their time in the sun, grass is brown and I just don’t like chrysanthemums much.  I stop and admire the gorgeous blue hydrangea but it’s not inspiring me to write about it.  I pick another trug full of beans but I’ve had beans for supper every day this week and don’t want to write about them.  I notice all the changes I want to make in my garden this fall and it just tires me out.

Then I come across my little Garry Oak tree, standing proud at the end of my ‘woodland’ path…well, it will be a woodland one day.  The mini mighty oak is newly planted this spring and, with the help of a bag of Sea Soil and diligent watering it has shot up about two feet and promises to be a strong anchor at that end of the yard in years to come.  But right now the leaves are looking awful…like they are sunburned.  That can’t be right, they were nice a week ago and we haven’t had much sun since.

Upon closer inspection I notice that the epidermis of the leaves, the surface, is being eaten away.  Hmmmm…is there a caterpillar in my midst?  I flip a leaf over and to my horror there is an ugly, ooey-gooey, slimy, greenish tadpole-looking thing stuck to the underside.  It’s like something out of an alien movie.  Almost transparent, definitely gooey and absolutely the culprit.

Folks, it’s the pear slug and it’s making its way to a neighbourhood near you.   The pear slug is the larva of the Pear Sawfly (Caliroa cerasi).  It generally enjoys trees such as Pear (thus the name), Cherry, Hawthorne, Mountain Ash, Quince, and, as in my experience, the mighty Oak.

This Sawfly actually goes through two generations a season (lucky us).  The adults emerge from the ground in early spring; lay their eggs in slits they make in the leaves, which then hatch into the slugs (which aren’t actually slugs).  The slugs feed on the epidermis of the leaves, until fully grown then they drop to the ground and pupate, putting forth the next generation.  The second set of adults pop out, lay their eggs which turn into more larva.  This is the time of the cycle where we see the most damage, when the second set of larvae is feeding and they make skeletons out of the leaves.

Although the pear slugs don’t really do enough damage to hurt the tree they do make it a tad unsightly.  Not to mention, who wants ooey-gooey aliens on their leaves?  Usually handpicking them is the best way of control or in my case, grabbing two bits of kindling (it was close by) and squishing the leaves and therefore the slugs in between.  A good shot of water will dislodge them but it may just hasten their decent to pupate.  As they are very soft-bodied Insecticidal Soap is effective but it must come in contact with the pest to work so if you can reach them just squish them.

So, that’s what I’ve chosen to start the fall season off with.  Ooey-gooey alien slugs and skeleton leaves.  Perhaps I should’ve written this one a little closer to Halloween.  Next time I think I’ll write about fall bulbs.  Less goo and more reward.

Shirley Eppler

September 2008