I have sixty house plants in one room with a southern exposure. I've noticed some fungus gnats have gotten quite a foothold in the plants, especially those I'm growing from seed. I've been using Ortho insecticide, but it doesn't seem to be doing the job and I don't want to keep spraying and possibly damaging the plants. Any suggestions most appreciated. These appear to be the only pests I have. I think its because I tend to water in the evening after I get home from work, and the water is not evaporating as quickly as it would if I were watering in the morning - is this a legitimate concern? Should I switch?