saw flies

It looks like this is going to be a great year for saw flies. My Explorer roses seem to be their favorite target right now. Any suggestions as to how to control them and hopefully avoid them in the future? Not growing the Explorers is not an option that I am willing to take, by the way.

Liz

Liz - Sorry to hear about the sawflies. I had them 2 years ago. Since they lay their eggs in the bud stem, which is apparent by that brown line on the stem, the stem must be cut off before they hatch. Since many pesticides recommened for them are now illegal/unavailable I found that spraying an outdoor fogger (like Off or Cutter) over the garden every 3 days or so, using the granular Bayer 2 in 1 for roses (fertilizer/pesitide) and spraying the ground around the plant with any garden use insecticide kept them from destroying everything. I also removed all the mulch from around all the roses the following spring. I use large wood chips on landscape fabric. I removed all the woodchips and hosed off the fabric. I would have removed the mulch in the fall but I need all the mulch winter protection I can get here in Maine. I did not have one sawfly last year, I hope I can say the same for this year. I don’t know yet because the plants are just starting to leaf out. There is not much info available on sawflies in the rose garden. Hope this helps. Lori

Thanks Lori. Yeah I had just a few last year and they really seemed to like Henry Kelsey but left the others pretty much alone. I ended up dealing with the larvae using a soap mixture. I have spent this morning flicking the adults off of the bushes and killing them if I could. I first noticed them swarming around some of my tulips and I wonder if that has attracted them in this year. I’m really trying to avoid using insecticides if at all possible, but this might push me into using one. I’ll keep you posted. By the way, I looked them up in the Encyclopedia of Rose Science and it looks like there are several types. I have the curling ones. It also mentions that they are becoming more of a problem in the US and Canada. And no advice what so ever in dealing with them. Liz

Liz - I hate using pesticides also. It’s going to be a tough year for bugs in the northeast this year because of the rainy spring. This morning my rosa spinosissima altaica finally bloomed and it is covered with brown bites and cut off buds which need further investigation. Last year the problem was all types of caterpillars, at least they’re easy to spot and remove. The lack of sawfly solutions is very frustrating. One interesting note is that my other rose garden with a white stone mulch had very few pest problems.

I’m interested to know if you’re using Henry Kelsey for hybridizing. This year for the first time I have op seedlings from Henry Kelsey, over 200! One has already bloomed with a similar flower only a lighter pink. I have several from John Cabot also. They are great roses and come as close to climbers as found in northern Maine. Where are you located? Lori

Here on the Southern California coast, we have Sawfly much of the year. In warm ones, they are nearly twelve month pests. If you don’t want to use “pesticides”, try Spinosad. It’s an engineered bacteria which replaces BT. Bacillus Thuringenisis only works on caterpillars, such as Tomato Horn Worm, so it isn’t of help for Sawfly larvae, which are worms. The Spinosad must be sprayed on the foliage and plants, upper and lower surfaces, about every two weeks during the pest’s season. The larvae eat the bacteria; the bacteria eat the worms! We’ve had no success using any of the systemic products as they are targeted against sucking insects, such as aphids, not chewing ones like the worms.

Fortunately, just about any spray type pesticide will kill the Sawfly larvae, as long as it is applied properly. But, if you don’t want to use pesticides, the Spinosad is a viable, organic alternative. You can buy Greenlight Spinosad or Monterey Garden Insect Spray as both are Spinosad bacteria. These can be sprayed on your entire garden, including edibles, as the bacteria is approved for organic gardening, depending upon the process the manufacturer used to create it. You’ll have to check the packaging to see which is OMRI approved, but both are useful products to control Sawfly, and a rather impressive list of targeted insects.

I was impressed reading the Monterey website to learn that BT lingers in the environment, replicating itself on corn plant roots and building up in water ways. The Spinosad will only persist in the environment as long as there are host insects to feed on. I’m also grateful that neither of the Spinosad products are as offensively stinky as the BT products are. I dreaded using BT because it has a horrible smell. I detect no scent from Spinosad. Unfortunately, I can’t say the same thing about Serenade, the bacterial fungicide, as it stinks to high Heavens! I hope the suggestion helps. Kim

Thanks Kim, Its nice to know that there is a non-pesticide option for dealing with the larvae. Just after I started this thread I decided to cut out quite a bit of the new growth that was showing signs of having eggs laid in the stems. Most of my rose bushes had this girdling of about half of the new growth. While this was a hard decision for me to make, this seems to have been very effective in reducing the larval feeding damage. Most of my roses are not exhibiting an signs of feeding damage and they have recovered from the pruning. I found this tip in the OMAFRA fact sheet that can be accessed from the page link below. Liz

Link: www.uoguelph.ca/pdc/Factsheets/PDFs/052RosePests.pdf

Liz, here in Southern Ontario saw flies can also be a problem. For me, they seem to be attracted to smaller plants. Perhaps they like the leaves closer to the ground. The product I use that seems to be the most effective is TROUNCE. It’s a Safer’s product. It seems to be a combination of Safer’s Soap and Pyrethrins. I try to use it a day after a rain. I would think the best time to spray would be early in the morning, but I often will spray after dinner. I haven’t noticed it burning rugosa leaves but rugosas rarely get saw flies. You could always try it at half strength if you are concerned.

Brantford Ontario Canada

Mark, thanks for the advice, btw you are just down the road from me - Guelph.

Have had them for the first time in Florida. Glad I came here to figure out what they are … looked for a while on google under wasps. They really are a huge bother this year all day long and they have moved from one end of my garden to the other. Guess I will be breaking my no spray rule as I have company this coming weekend. I hope it helps.Thank You

Andrew

I’m wondering if anyone else is having a HUGE infestation of sawfly like I am?! In just under about two weeks nearly ALL of my roses are showing some sign of them. I see Kim replied with some organic solutions 10 years ago. I picked up a bottle of Earth-tone Insecticidal Soap a few weeks ago, active ingredient Potassium Salts of Fatty Acids (1%) but there’s no way this will control the problem. Has anyone else used Spinosad with good results in an organic setting? I haven’t sprayed my roses (or any part of my garden) with any pesticides in years and don’t want to disturb whatever balance I’ve struck. I see birds landing on the roses trying to eat the sawflies but I’d need a whole flock of angry birds to get them all. And I don’t want to hurt the birds or the bees. Any advice?!?!
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Spinosad is a great product, use with a pressurized sprayer for good upper and lower leaf coverage as noted by Kim. Another good (and organic) product is AzaMax. I used to be plagued by sawfly but now rarely have to spray. Break the cycle and they will stop (unless you have lots of negligent rose growing neighbors). I also think that using liquid silica is a good choice-anything to make the leaf structure thicker, tougher seems to help. This is all that I have used on my neighbor’s roses, which used to look just like your photo above, and the flies are noticeably absent this year. I use all three products as needed, but apply the silica when the roses are actively leafing out in early spring. For the past two yrs all I have used is the silica. None of these seem to work real well with grasshoppers, which primarily go for the newly forming buds, but I have not tried them both with often enough application to possibly intercept the worst of them. I lose a few flowers but the plants are not thoroughly ravaged as by the sawfly.

Thank you Jackie! I will try any and all of those suggestions. This is the worst I’ve ever seen them so hopefully I can break the cycle as you say.

The “hope” in all of this is, as the climate heats and dries, sawfly and other “greenhouse condition lovers” will become less and less issues where they traditionally have been. They, and aphids, hate hot, dry conditions, and tend to be found in more sheltered spots where the cool, damp are less. They, and white fly, were issues at the bottom of the ridge I lived on in Encino, but never up on the ridge except in sheltered spots where moisture was trapped and the wind and sun couldn’t reach to dry and heat up. Just eight miles east, in Sepulveda Pass, the same distance from the actual beach, where the coastal influence was major, fungal issues, white flies, saw flies and aphids were constant and legion. Destroy the “greenhouse conditions” and you eliminate the pests, but you also open the door for spider mites, which adore the hotter, drier ones.

Here in Santa Maria, where the air is twenty to thirty degrees cooler than Encino and the humidity is much higher, sawfly is only an issue up close to the house or under the liquid amber trees in the back of the yard where the hotter sun doesn’t penetrate. None of the roses exposed to all day (or most of the day) sun have any evidence of them, but those protected by the semi to full shade are rather badly eaten. I would see similar results in clients’ gardens in the Santa Clarita Valley, also. White and saw flies were seldom issues, except in very sheltered, protected spots where they would flourish unless controlled.

Thanks for the intel Kim. Most of my garden is semi-shaded at various times of the day and we did have some "June-gloom"y mornings here in Santa Monica. I’m sure that contributed to the sawfly explosion. Aphids haven’t been a problem nor has powdery mildew I’m happy to report. Expecting warmer weather ahead (which will likely let the rust bloom!) but I’m going to try Jackie’s and your suggestions this week. I don’t want to stress the plants out so much that they abort their hips.