QuestionI live in zone 6 and have a climbing rose on the the east side of my house. Something bores into the canes and then some kind of larvae eats the leaves over the course of the spring / summer so that they become all lacy. The local nursery suggested that they were fly larvae (eggs laid in the bores made by the fly). He suggested a systemic insecticide but this resulted in a couple of dead birds under the bush - Any idea what this is, and what to do about it safely?
AnswerFrom your description I am sure you have stem borers. There are three different kinds one you can identify by the twisting trails around the canes but all usually attack the new, soft rose canes . The fly bores down into the rose canes and lays the eggs . The eggs hatch and the young feed on the inside of the cane causing it either to die or be damaged. They don't eat the leaves but because they damage the canes, the leaves will wilt and die. Using any chemicals on them is useless as they are well protected by the tough outer bark of the rose canes. You need to cut the canes back past the damage they have done and then burn them. Sometimes you can actually see the tiny hole the borer went in. But they can easily get in after you have cut a flower as this leaves an open cane. A drop of Elmers glue after cutting rose or pruning, blocks them off.
Some other insect is eating the leaves. If the cuts are large and have neat edges it is probably beetles but if the edges are small and rounded then it could be caterpillars. You can use Safers Insecticidal Soap or you can make your own but you have to use real soap such as a bar of Ivory soap. Liquid Ivory dish soap is not pure soap. It is the fatty acids in the pure soap that does the insects in. I quart of water and mix in teaspoon of melted ivory soap pus a few drops of canola or corn oil. Shake and mix well. If the soap starts to solidify then use warmer water.
Using a systemic insecticide will kill all sorts of good insects and when the birds eat them, they too are also injured by the spray.
