My lawn is under attack these days by some type of insects. It has already damaged my couple of flowering plants of Gerbera and rose. Insects have attacked about 30-40% of plants, some flowering and others ready to flower. Here is one picture showing my damaged gerbera plant.

I had already bought Lambda-cyhalothrin insecticide. Can it be used to get rid of the above insects? If yes, how to use it?
Javed.