The aim of the present study is to propose an IPM method using decision rules for global management of greenhouse crops which are environmentally friendly, such as use of beneficial organisms, no pesticides, etc. Decision rules could be considered the good means for the implementation of IPM in greenhouse agro ecosystems. Decision rules based on the thresholds of pests could be developed as a basis to control rose and tomato crops. Global management action has to be directed against the several pests that are present simultaneously or successively. The strategy will be preventive, and makes use of pest abundance evaluation to choose the best rule. Use of beneficial organisms is the first action to be chosen in these decision rules. If the use of pesticide is necessary, its side-effects must be as low as possible. The results obtained on previous IPM studies were used to write complete sets of decision rules. The sets of decision rules to manage whiteflies that affect tomato and rose crops are presented. They answer the question asked and are written on the form "if-then"with a scale of actions if they are numerous. Applying these rules, satisfactory results were obtained to manage whiteflies e. g. Trialeurodes vaporariorum or Bemisia tabaci by using Macrolophus caliginosus and Encarsia formosa for tomato and by using Encarsia formosa and/ or Eretmocerus eremicus for rose. The pesticide use was considerably reduced.