Under the guidance of system control, the integrative effect of 11 controllable factors of soybean yield on threespotted plusia ( Argyrogramma agnata Staudinger ), natural enemies and summer soybean yield was studied from 1993 to 1996.The results showed that the main factors affecting threespotted plusia were planting mode, trace fertilizer, sowing time and potassium fertilizer application. The most important factor affecting the natural enemies was the planting mode. The main factors affec...