Damaged Budding Rose
We cannot say what is going on with the rose bud. We notice a parasitized aphid on the sepal which is good. The aphid was parasitized by a type of wasp which is natural pest control at work.
It is possible you may be dealing with a type of physical or mechanical damage to the bud. Cut off the bud and see if you have more symptoms. If so, send us more photos so we can take another look.
A common pest of rose foliage is rose slugs. Keep any eye out for this.
The adult is a sawfly and resemble wasps. Larvae are about 1/2" long and yellow-green with yellow heads. The larvae skeletonize the leaves and in heavy infestations can cause leaves to turn brown and curl. They do the damage. Look on the undersides of the leaves for the young larvae. If the infestation is light, pick off and destroy the larvae by hand.
To control heavy infestations, use horticultural oil (summer rate) or spray with spinosad. Target the undersides of the leaves. Follow label directions. Do not use homemade sprays as this can be phytotoxic to the foliage.
See our website for more information and photos.
Is insecticidal soap also horticultural oil? When I typed it in the search on Lowes.com, insecticidal soap and garden insect killer came up.
Hi - No. Insecticidal soap and horticultural oil are different products and they work on insects in different ways. Here is information about the differences between the two. https://hgic.clemson.edu/factsheet/less-toxic-insecticides/