Here’s a recipe for an inexpensive insecticidal soap that won’t harm your plants. This soap is effective on aphids, scale, and other soft-bodied bugs, but it won’t kill hard-shelled bugs — however, the garlic and onion is supposed to repel them.
Ingredients:
1/4 to 1/2 of an onion
2 T minced garlic
2 T pure castile soap (I use Dr. Bronner’s lavender - which contains oil as well)
1 1/2 quarts water
Put the garlic and onion in a mason jar or similar container. Pour boiling water over the mixture and let steep for 24 hours. Strain and add the soap to your mixture. Mix well and spray directly on the offending bugs. Best to spray on a calm day, early in the morning. For a little extra repellent action, you can bury the onion/garlic pulp where you have the worst bug problems.
PS You can plant chives next to your roses for an effective aphid repellent!