The yield and/or the vigor of an agronomic plant can be increased or improved in locations where the level of insect infestation is below that indicating the need for the use of an insecticide for insect control purposes by treating a seed of the plant with a neonicotinoid compound. The method is useful for non-transgenic plants and for plants having a foreign gene that encodes for the production of a modified Bacillus thuringiensis delta-endotoxin protein. A method of improving the results of a plant breeding program, a method of marketing plant seed, and a seed that has been treated by the method are also described.
