These milkweed plants are being consumed by aphids while the blueberry leaves inches away have no aphids on them at all. This is a clear indicator that the soil microbial population and mineral balance is more supportive of blueberries than it is of milkweed.
The aphids are attracted to the unhealthy plants, and are taking them out of the ecosystem. If the milkweed were healthier than the blueberries, the aphids would be on the blueberries, and leave the milkweed untouched.
Since the aphids are now consuming a plant that might be considered a ‘weed’ in this particular context, does that make the aphids a pest for attacking the plants, or a beneficial ‘biocontrol’ because they are removing the ‘weed’?