I have what I think is a very bad infestation of a long blade weed with light green color. I assume it is nutsedge. Any advice on what really works to kill it? I have a so called professional lawn service treating my yard and it is spreading everywhere.
Most lawn care services do not treat for yellow nutsedge unless you request it.
You can treat it yourself using spot treatments with products containing any of these active ingredients (see label)...
Halosulfuron-methyl, sulfentrazone, or bentazon.
Examples of products sold in stores for nutsedge control include Sedgehammer, Nutgrass Killer, Nutsedge Killer, Basagran, Manage, and others.
Make two applications, 10-14 days apart, when soil is moist and plants are actively growing. Avoid mowing 3-5 days before and after application if possible. Do not water the lawn for 1-2 days after treatment.
Seeds and tubers remain in the soil for several years, so treatment will also be needed next year.