Disclosed embodiments concern a process for controlling plant pests, such as insects, nematodes, fungi, weeds, and combinations thereof, with specific embodiments being particularly useful for weed suppression. One disclosed embodiment comprises providing a plant, or a portion thereof, selected from the family Brassicaceae, particularly from the genera Brassica and Sinapis, and even more particularly from the genus Sinapis. Plant material is applied to soil prior to crop planting, simultaneously with crop planting, or subsequent to emergence of desired plants. The method may further comprise processing plant material. For example, with reference to Sinapis alba processing can include crushing the plants to obtain seed meal, which can be applied as obtained, or can be in other useful forms, such as pellets. Alternatively, effective glucosinolates may be extracted from plant material, either with or without first pressing the plant material. Extracted glucosinolates are applied to soil, followed by applying myrosinase, or alternatively the glucosinolate and myrosinase can be co-applied, to soil. Plant material or processed plant material may be combined with at least one additional material to form a composition, such as natural pesticides, natural fertilizers, synthetic fertilizers, synthetic herbicides, synthetic pesticide, surfactants, binders, colorants, pH adjusters/stabilizer, capsaicin, onion tissue, one or more microorganism, one or more products provided by a microorganism, or combinations thereof. The method also can include controlling the amount of water and/or pH added to soil, and or pH, to which the plant material, processed plant material, composition comprising plant material, or composition comprising processed plant material, is applied. The water and/or pH is selected to maintain bioactivity.