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Goulburn Valley Fly Fishing Centre

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Willow Sawfly

The willow sawfly or willow grub, has quickly attained legendary status among the fly fishersWillow grubs are voracious and love willow leaves of south east Australia. In the few short years since they first appeared around 2005, they have proliferated to the point where it is hard to find trout feeding on anything other than Nematus oligospilus. As such they are an extremely important part of the trout fishing season and one that require further examination.


Willow Sawflies arrived in Australia sometime in the middle of this decade. While native to temperate climates of the northern hemisphere, they have thrived in similar environments below the equator, particularly in Chile, Australia and New Zealand.

According to the CSIRO, these insects first appeared around Canberra in 2005. According to our log books we listed them here without knowing what they were in that same year. Over the past 12 months reports from all over north east Victoria place them in huge numbers right across the region. It appears only a matter of time before all of south east Australia is recognised as having populations of this voracious insect.

Officially CSIRO, DPI and the like are saying that the introduction of Willow Sawfly was an accident and not part of a deliberate plan to eradicate willow trees, a species considered a pest by many within the environmental movement. There are some who doubt this claiming that they were deliberately released into Australia to combat willow infestation. This theory has little credibility as the introduction of one pest to remove another is unlikely given our history of failed attempts in the past.

The Grubs
A floating grub with a number that have sunken lying on the bottom

Willow grubs are not large with the larva typically reaching about 20mm length. Adults are only about 6-8mm long. While both stages of the life cycle are important to the fly fisher, it is the larva that is fished most often. Hence when we say grubs in this piece we will be referring to the larva of the Willow Sawfly.

The grubs vary in both size and colour. Larva found on a single tree may be straw coloured to lime green as well as every shade in between. As fly fishers we typically find that lime green versions are the most successful when imitating this insect in the larval stage. The grubs infest willow trees and totally denude them of leaves, sometimes in a matter of weeks. While bare branches are the hallmark of sawfly infestation, damaged leaves will often be the most noticeable feature pointing to the presence of these grubs.


Despite recent publications in the fly fishing media on the topic, willow grubs are a very important part of our fishing from November onwards. The oft quoted time of Christmas onwards is so far off the mark as to be ridiculous. Most of our trees have been stripped bare by this point in time.

We have had great fishing with willow grub hatches from the start of November the past two seasons. Localised to begin with, they soon spread far and wide, eating their way down the river. The fish switch to them almost the moment they start falling in and don’t stop until they are gone! That’s the longest rise in Australian fly fishing with at least three to four months fishing as a result.

How the fish respond

The willow grub hatch is not actually a hatch but a fall. A massive fall of grubs that goes on all day, every day from the moment they appear. We are talking a nonstop lemming (yes I know lemmings don’t fit their stereotype but the stereotype fits this description) type drop from the streamside foliage into the rivers.
high contrast shot shows the willow grub on the water's surface and the indentation made as a result

The huge number of insects falling onto the water and drifting in the bubble lines, causes a frantic rise by the fish. The trout really key into the ‘blip’ that each grub makes when it hits the water and will actually come 4-5 metres across the drift to take one. Most of the time however the fish will sit in strong bubble lines and simply rise as if on timer every few seconds until the heat from the day fades and the grub’s activity wanes.

This leads us to the real dilemma of fishing this hatch. What do we know about selective feeding from Schwiebert and the like? Well we know that the more prolific and insect, no matter how small in size, the more locked into that food source the fish will become. Selective feeding leads to fish locking onto the key aspects of the food item. Size, shape and colour with presentation the final ingredient required for success.

Matching the Hatch

Are there any commercial patterns available that fit the bill? Not as yet but we will have them ready for this season’s fishing (October 2009). Over the past few years we have played with every type of material in various shades of green and have finally settled on a couple of designs. The search for the right material took a long time but once we found it the catch rate went through the roof.

You can see in the photos how the willow grubs look when on the water and sinking. Upon contact with the cold water the grubs curl up in a C shape. That is the shape we need to mimic; to get the fly to sit horizontally on the surface in a C shape. This requires some careful shaping of the foam with scissors before attaching it to the hook.James' variation on the willow grub. Simple and effective.

The size of these insects is approximately 6-8mm and I tie them on a fine gauge dry fly hook of about #16. Ok the hook is too big for the insect from the traditional flytier’s perspective, but it’s the shape/size of the body that is important i.e. that the fish locks onto. Not to mention the fact a smaller hook with foam used in this way will result in missed takes.

The green colour we settled on can be seen in the photos. Those interested can pick up some sample flies from us when next in the shop this season.

Fishing the Grub

The good news about willow grub fishing is that the fish are completely transfixed by them. Such are their numbers that the fish lose all track of their own needs for preservation. Obviously not totally, but enough that you can get right up close to get the perfect presentation to them.

A willow grub riser will be rising frantically and in most cases, assuming that you have the correct fly, its more about timing your presentation to arrive at the precise time that the fish is set to rise. This may sound farfetched but once you fish this hatch you will appreciate it. The fish will get in a rhythm depending on the speed of the water and the number of bugs (which is always heaps!). Sometimes the rises will be 2 seconds apart for fish sitting high to the surface (literally within 3-4 inches) and sometimes it may be every 10 seconds. The trick is to spend a few minutes getting the feel for this rhythm in order to present at the correct time.

This can lead to ridiculously frustrating fishing with fish rising literally a second either side of your presentation. The good news is that they are so focussed on the food that you will be afforded the luxury of dozens of presentations.The grubs sit on the surface anywhere between straught and in a curve. The curve on the right is the most common version

Accuracy is very important as it always is. Drifts are standard affairs with a dead drift, free of drag the only way to go. Try and put yourself in a position where your leader/line will all land in the same amount of current i.e. minimising the potential for drag. When in backwaters and slower side waters, creeping up and hiding before making short bow and arrow casts will work very well.

The Sinking Grub

As with most terrestrial insects that fall into the water, those not quickly eaten or able to find their way to safety, sink to the bottom of the stream. Fish will lock onto these sinking grubs, taking them exclusively. It is worth tying up some sinking versions or even keeping the more sparsely tied foam ones that fail to float for this very reason.


Our willow grub or sawfly is here to stay. We have had four of the best dry fly seasons ever as a result of their sudden arrival and this year is shaping up to be another great one with another warm season ahead.

As we have figured out the pattern, you simply need to either purchase some or get the materials and instructions from the bottom of this page and tie your own. Then watch our website and head up when we start reporting on them to put into practice the instructions given here on this page. You will be amazed with the results.


PS- those wishing to short cut the entire process or simply maximise their time on the water can employ one of our guides to show them the ropes. We are available by the hour, half day or full day.




Willow Grub - Antony's version    How to tie the australian willow grub (sawfly) fly pattern   


Hook: Light gauge Curved grub hook

Thread:  Green 8/0 Uni-Thread

Body: Green Foam - available Spotlight




1/ When tying this fly, hook selection is all important. We have come to the conclusion that a curved hook works best, the finer the gauge the better. All hook manufacturers make a version to suit. Once you have your hook, secure it in the vice and wrap a base of thread, stopping somewhere in line with the hook barb.

How to tie the australian willow grub (sawfly) fly pattern

2/ Take some foam and cut it to shape. Its almost boomerang shaped, the idea to represent the C shape that the grubs immediately take once they fall onto the surface of the water. The best way to do this is to cut several pieces at once. I have included some examples down below as seen against a 5c piece. Personally I like a greater curve as per the photo on the right.


How to tie the australian willow grub (sawfly) fly pattern

3/ Start tying the foam onto the hook by tying at approximately the 1/3 point of the pre-cut foam body. As you can see, I lash it to the side of the hook rather than the top, as this is the way we want it to float. Make half a dozen tight wraps in the same plane, being careful not to cut/damage the foam.



How to tie the australian willow grub (sawfly) fly pattern

4/ This is really the same step but a different view. As seen from above, the body now has a section that kicks out at an angle from the hook. This is first part of creating the illusion of a C shaped grub on the surface. Note again that we have not tied the foam on top of the hook but rather to the side.

How to tie the australian willow grub (sawfly) fly pattern
5/ Now skip wrap the thread to a point approximately 1/3-1/4 of the hook shank length back from the hook eye. This is where the next stage will be added and the fly pretty much completed.

How to tie the australian willow grub (sawfly) fly pattern

6/ Do exactly as you did in step 4 and tie the foam onto the side of the hook, so that the body sticks out at an angle to the side. Half a dozen wraps should be ample to secure it, remembering to not damage the foam in the process.

How to tie the australian willow grub (sawfly) fly pattern

7/ Once again this is another view of the same step. As seen from above, tying the body to the hook at the 1/3 and 2/3 points has created the impression that we have a curled up grub floating on the surface. Of course it isn't a perfect C, but it is as good as we can get using the materials that we are forced to use, and also when considering that an exact imitation will spin and cause presentation problems.



How to tie the australian willow grub (sawfly) fly pattern

8/ Now to finish you can simply use a couple of half hitches or whip finish but I like to do one more thing. Wrap the thread over the top of the body using a small amount of pressure to create a sort of segmented appearance. Take 2 wraps to go to the rear tie in point and a further two to make your way back to the forward tie in point. Then simply finish the fly. This step is often skipped as these extra thread wraps and come apart and a being removed from the sharp teeth of a trout.

How to tie the australian willow grub (sawfly) fly pattern
9/ The finished fly as seen from above. This is how it looks floating on the water. It is deliberately tied about 30% oversize as most fish will still take it at this size and it floats well. A small pair of scissors should be carried in case of a refusal. A small trim usually sees any picky fish come to the party.

How to tie the australian willow grub (sawfly) fly pattern

The Pattern
How to tie the australian willow grub (sawfly) fly pattern

For the past few seasons we have been playing with patterns to correctly imitate our local fall of willow grubs. This ubiquitous terrestrial has quickly become a staple food item of our trout from November to March of each season. During the process of developing this fly, there were many dead ends. We played with numerous materials and construction techniques trying countless combinations over a two year period, before finally cracking the code.

The answer lay in the foam that we were using and also the way in which it was cut and applied to the hook. Many earlier versions used this exact foam, but due to the method used in tying the fly, they mostly spun and caused damage to tippets. They also started twisting when on the water as the spinning tippet tried to straighten. How to tie the australian willow grub (sawfly) fly pattern

After much gnashing of teeth and stuffing about, the answer was found. The foam had to be cut to suit the curled shape of the grub and then simply attached to the hook. This allowed for a curved shape yet at least a third of the body in the centre section, being lashed to the hook. This solved the spinning problem. Then after a little bit of trial and error, we settled on a specific colour in the foam that worked more often than not.

This foam is not specifically aimed at the fly fishing market. As a result it comes in large quantities/colours for relatively little cost. Spotlight stores carry it and it costs about $20 for 40 Sheets. It measures 6”x9” and has an adhesive back making it also fabulous for hopper bodies and Chernobyl ants. It is made by Darice and called FOAMIES. www.darice.com

Geoff has his own version of the fly, tied completely differently, as does James. These will feature at a later date.

Go fishing.....





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