We laid new sod about 2-3 months ago, and it has been growing beautifully. Recently, though, there seems to be an influx of these green, leafy, spinach looking weeds that have been popping-up ALL over our lawn. Usually, I just pull them out. Lately, they have been increasing in numbers and I'm started to get annoyed.

My landscaper has been adamant about NOT using any fertilizers, or treatments on the lawn. But is there anything that can be done to zap these things that keep popping-up?