Yes, I grow this plant for quite a few years now. But, since I like to use the leaves in cooking, I have never used any pesticide on it. I grow my plant in Summer outside, where I never let it dry out and it is certainly well ventilated.
Now having said that, I take my plant inside in the Fall and at this point it is really clean and seemingly bug free. I use the leaves fresh about until the end of the year. I have never done it, but it is probably a good idea to harvest some leaves in the Fall and freeze them as my plant is very susceptible to small brown scale invasions. At this point I simply cut all leaves off and throw them out. By early Spring the plant shows new growth.
I would think good ventilation is very important and good light. Even when the plant is almost dormant for me here in NJ, I still water a bit, but I increase watering when I see new growth.
I wonder if your plant was perhaps not well ventilated/kept too shady?
