I walked out to my pond to feed my koi this morning, when I noticed some yellow spots on my volunteer gourd plant. Upon closer inspection I noticed it was infested with aphids. I will not claim to never use chemicals in my garden but I would say for the most part, I do not. This is why I will be spraying the aphids with a 1% soap mixture to kill them. In other words, use two Tablespoons of dishwashing liquid per gallon of water. Spray to the point of runoff and make sure you get the underside of the leaves, especially when they are as bad as on my poor gourd plant. The University of Florida has a great article if you want further reading.