|one of my 4 rose bushes buds out then they fail to open|
|Without seeing the rose buds and carefully inspecting them, it's difficult to make a positive diagnosis. If the rose bush looks healthy and the buds simply fail to open, his condition is most likely a physiological problem that occurs following alternating dry and wet weather, mild temperatures and cold spells. Poor nutrition can also contribute to this failure to flower. Give your rose some extra care by mulching the soil well to reduce soil temperature fluctuations and feeding with a high potash complete fertilizer, or phosphate rock and greensand.
On the other hand, the symptoms you describe could indicate damage from rose weevils (also known as Curculios). Weevils feed on the rose buds and flowers by puncturing and sucking the juices. After that they lay their eggs in those same buds and when the larvae hatch, they feed on the petals and the receptacle area. If any flowers manage to open, you will notice distinct small holes in the petals that were made by the adults. The adults drill small round holes deep into the flower buds and hips for feeding and egg-laying. Eggs are usually laid in the hip or ovary and the small white larvae feed on the reproductive parts. The greatest damage to roses is cause when adults feed on flower buds. The adult punctures the floral parts contained inside buds. Later, if the flowers suceed in opening, these flower parts are riddled with holes, resulting in ragged , unsightly blossoms. You can check for these pests but cutting open a few of the unopened buds. You may see the larvae or the damage they have done. The best control is to pick off the affected rose buds before the larvae can exit and turn into adults and start the process all over again.
Best wishes with your roses!