This agriculture extension service publication from Pennsylvania State University examines agronomic weed problems and control. Contents include a listing of the characteristics of weeds, a section on herbicides, and a section on the important weeds of agronomic crops in Pennsylvania. The herbicide section discusses systemic herbicides, contact herbicides, time and method of application, structure, herbicide formulations, herbicide-fertilizer combinations, herbicide use safety, and herbicide persistance factors. The important weeds section examines Horsenettle, Johnsongrass, Nutsedge, Quackgrass, and Wild garlic. (MR)