In nature, plant diseases, insects and parasites (hereafter called as "pest") must be co-survived. The most common expression of co-survival of a host crop to the pest can be tolerance. With tolerance, chemical uses can be minimized and it protects environment and sustains host productivity and the minimum pest survival. Tolerance can be applicable in all living organisms including crop plants, lifestocks and even human beings. Tolerant system controls pest about 90 to 95% (this pest control system often be called as horizontal or partial resistance), while the use of chemicals or selection of high resistance controls pest 100% (the most expression of this control system is vertical resistance or true resistance). Controlling or eliminating the pests by either chemicals or vertical resistance create new problems in nature and destroy the co-survial balance of pest and host. Controlling pests through tolerance can only permit co-survive of pests and hosts. Tolerance is durable and environmentally-friend. Crop cultivars based on tolerance system are different from those developed by genetically modified organism (GMO) system. The former stabilizes genetic balance of a pest and a host crop in nature while the latter destabilizes the genetic balance due to 100% control. For three decades, the author has implemented the tolerance system in breeding maize cultivars against various pests in both tropical and temperate environments. Parasitic weed Striga species known as the greatest biological problem in agriculture has even been controlled through this system. The final effect of the tolerance can be an integrated genetic pest management (IGPM) without any chemical uses and it makes co-survival of pests in nature.in nature.

• Soon-Kwon Kim