Question
Hi Lynette,
I am a volunteer at Point Ellice House here in Victoria B.C. I'm trying to solve the problem of buds which form well, shapely and full, but the edges of the petals turn brown and the buds don't open. The bush appears to be healthy in all other respects. I hope you can help. Thankyou. Maris.

Answer
What you are describing are thrips that damage your roses. The female  makes a tiny slit in the bud or new growth tissue, then lays eggs. After a few days, the eggs hatch and go about sucking plant fluids until they get fat enough to pupate, commonly in the soil. One species, the Western Flower Thrips, sometimes pupates in plant litter at the base of the rose bush or protected areas on the plant as well.
Eventually they emerge as a flying adult, mate, and the process renews. This whole life cycle, from egg to adult, takes only about two weeks during warm weather, and about a month in cooler weather.
Damage to the rose bud is most noticeable in light colored roses, although thrips may attack all roses they seem to really prefer the white or pastel coloured ones. If the buds open at all, the petal edges may look brown or discolored. Sometimes the buds will only partially open. Sometimes, the buds will simply wither and die.
A technique for checking for thrips, is to take a blossom and, with your fingers, pull back the petals. If you see small slivers of creme, yellow or brown, scurrying about headed for cover, these are the  larvae of the thrips. They are very tiny to the naked eye.
They do have some natural enemies such as a tiny wasp but if the infection is large, they really aren't of much help.
Adult thrips and larvae prefer to hide in complex plant parts, flower buds and other folded tissue where they are difficult to detect and to reach with insecticides. Therefore ordinary insecticide sprays will usually not kill most of them. The answer is a systemic type spray which gets into the sap of the rose and when the thrips feed, poisons them.
To discourage thrips from attacking, spray plants with a systemic insecticide just before the buds open. Don't forget to spray all around the base of the rose bush because that is where they pupate. If signs of thrip damage appear, remove and destroy infected flowers and buds. If the infestation is severe, repeat applications may be necessary. Gardeners arsenal of pesticides is getting very limited which is a good thing for the environment  but causes a lot of problems with insects like thrips which are very tiny and very difficult to keep under control without a strong insecticide.
If a garden has been infected with thrips one year, there is a good chance the insects will return the next year.
Rose cultivars with sepals that remain tightly wrapped around the bud until blooms open have fewer problems. The problem with controlling thrips is that insecticides work well on the early stages of their developement but when they are down deep in the rose petals, are much  harder to get as they are well protected. Rose midges are not easy to get rid of and you have to stay on top of them. Burn or put into the garbage, all dead flowers and if possible try and keep the base of the rose bushes free of plants as this makes an ideal hiding place. Here is a positive note for you. If you have rose midges they will get rid of any spider mites. Alas too high a price to pay.