Here, the speaker looks back on a time when they were a rose, healthy and self-sufficient, planted in a garden and able to give themselves everything needed to grow. The title points to the shift: aphids are tiny insects that feed on plants and weaken them. The "you" in the poem is the aphid, someone whose arrival ruins that independence.
The speaker's feeling is bitter and hurt. Calling the other person's presence a curse is blunt, and the casual "Well," before the turn sounds like a sigh, as if the speaker is still absorbing what happened. The person didn't only stunt their growth; they also passed on a "virus," which suggests damage that lingers rather than ending when the person leaves. The last two lines are the sharpest: the harm "continues to foster" the speaker, a strange use of a word that normally means to nurture. The mood is quiet, resentful and wounded, with a sense that recovery is still far off.