I think we’re winning in the war on aphids. The basil and arugula seem to have many fewer aphids. There are less than a handful of healthy aphids per pot, and the rest are a dark brown colour which seem to imply death or sickness. Most of my basil is thriving; they’ll be ready for a pruning soon. My arugula haven’t fared nearly so well; only the biggest plant looks like it’s going to survive.
One of our friends, who is a graduate student in entomology (specialty: bed bugs), told us that in fact, soapy water will work, because anything alkaline will. Since using soapy water is a lot neater than sacrificing/chopping/steeping tomato leaves, we started using that. If anything, it’s even more effective than the tomato leaf spray.
I looked it up, and I found this fact sheet published by Colorado State University Extension (I love land-grant colleges). According to it, soapy water works on direct contact, so you really have to cover the offending insects with it. I was also a bit too blithe in my application of it; there is a strong possibility of harming the plant. Moreover, not all household soaps and detergents are effective.
But it worked for us, no harm done to the plants (well, to the basil anyway, I’m not so sure about the arugula) and most of the aphids are dead. I’m glad all my hard work paid off. I spent quite a bit of time spraying each affected plant every day, making sure to get the stems and leaf undersides. To be honest, I’m a little sick of it. I’m glad that most of the aphids are dead now, so I can spray every once in awhile instead of daily.