Hello Everybody - I've been trying to figure out an effective way to control the nasty Leaf Miner problem with the Weeping Birch that we have in the back yard. I know that I am guilty of not taking as good of care as I should have, but we were away all summer and It's not a good looking tree right now. I'm pretty sure the Bronze Borer hasn't shown up yet, so I would like to try and save the tree. Through the research I've done, I know some things, like the fact that Cygon and Lygon cannot be used anymore, and I also know the life cycle of said miner. What I would like to know is this: if the life cycle of the leaf miner starts with the hatching of the pupa in the ground in May, why not cover the ground with a large plastic sheet which would prevent the sawfly from proceeding to the leaf to lay eggs? If one was to water the ground first and monitor the arrival of the bug, wouldn't it be possible to prevent futher damage? Couldn't a person apply a mild insecticide under the plastic to help subdue the little critter? Any opinions would be appreciated. Thanks Bill
We rehabilitated an old, suffering weeping birch in our yard in Edmonton by two means: 1) digging out the sod (and adding soil, and planting perennials), and, 2) assiduous watering. Digging out the sod may have reduced the number of miners in the soil, but providing enough water to restore its health (reducing drought stress, which affects birches very commonly in our dry climate) was probably the biggest factor. We've done the same in this yard here in Calgary (again, watering being the biggest factor, I believe) and have reduced birch leaf miner to next to zero (infestation was very noticeable when we moved in), and apparently staved off borers from affecting our two clumps of European birches. By contrast, most of the other birches in the neighborhood have the usual dead tops from birch borer.
Was the removal of the sod much of a chore? With the roots being so close to the surface, I would think you could damage them in the process. It does make a lot of sense to remove the sod (which we do have) because this would remove the pupa and also allow us to apply a layer of mulch. I read somewhere that mulch was the way to go v/s sod. While I'm at it I will remove all the softball sized rocks I have placed around the base of the tree. I'm guessing this was not a good idea. What would be the best way to remove the sod??
Well, I think most people find digging out sod to be a bit of a chore, yes. I think the value to removing the sod is perhaps that some insects are removed (but bear in mind that they could rapidly recolonize from all the other suffering birches in the neighborhood) but more likely that grass competes very effectively for our scant rainfall and the little watering that people do, to the detriment of the birches. I think perennials as a groundcover, or just filling with a bit of compost then up to the former level with mulch, results in a lot less water competition for the birches. (If you doubt this, water your lawn for 10 minutes - the typical time expanse that people set their in-ground sprinklers on for - then cut out a square of sod with a spade and actually see whether water has penetrated through the sod layer - chances are it has only wet the grass blades.)
No doubt about the grass absorbing the water. The part I was wondering about was how to remove the sod without damaging the roots. The only safe way would be to pull it up carefully by hand utilizing small hand tools being careful not to damage the roots. I just finished removing the rocks. Do you think the rocks may have caused any problems , as in pinching off the roots and preventing a good flow of liquids?? Thanks for you replies Bill
Err, well, do as you like but I don't really think there's any need to overcomplicate this. Most of our grass removal (i.e. all of our 1/3 acre well-treed yard) has been by flat-edged spade. We just used to make lines of cuts vertically through the sod layer, then across, to result in a grid of pieces of a size to be easily dealt with, then just slide the spade horizontally under the compacted grass root layer; shake as much soil off as possible. Once an area has been cleared of grass, don't delay to add soil and a capping layer of mulch up to the former level (i.e. do it the same day or ASAP to avoid letting exposed tree roots dry out). Yes, some shallow feeder roots will be damaged. We haven't seen any effect as a result of removing all the sod in our yard. Assuming the tree was there long before the rocks were, the rocks won't have pinched roots, and if anything, would have allowed better water penetration if they were on top of soil than sod would. The problem is usually not enough water to maintain the tree's health, and essentially help it resist the effects of insect infestation.
I went out and tried to lift a little sod by hand to see how tough it would be. This was after I had applied water for about an hour with a spray type of pattern. The result was moist sod, dry under the sod. No surprise there. I have moved a lot of sod over the years, by hand and with a sod removal machine. The only reason I was worried about the roots is because I read that you could actually damage them with a weed eater or lawnmower. This made me believe that the roots are very delicate. Based on your input, I will be using appropriate tools to make this less "complicated". Just to get back on topic, what do you think about using a sheet of poly to trap the sawflies as they emerge?
