We present in this paper a new multiobjective memetic algorithm scheme called MEMOX. In current multiobjective memetic algorithms, the parents used for recombination are randomly selected. We improve this approach by using a dynamic hypergrid which allows to select a parent located in a region of minimal density. The second parent selected is a solution close, in the objective space, to the first parent. A local search is then applied to the offspring. We experiment this scheme with a new multiobjective tabu search called PRTS, which leads to the memetic algorithm MEMOTS. We show on the multidimensional multiobjective knapsack problem that if the number of objectives increase, it is preferable to have a diversified research rather using an advanced local search. We compare the memetic algorithm MEMOTS to other multiobjective memetic algorithms by using different quality indicators and show that the performances of the method are very interesting.

The insecticide application techniques on cotton were compared in a series of trials. The new techniques compared well with knapsack sprayers and can play an important role in the control of Heliothis and other insect pests of cotton in Zambia. The ‘Electrodyn’ knapsack and ULV sprayers gave similar yields and pest control with cypermethrin at 30 g a.i./ha. A new pyrethroid lambda cyhalothrin (12 g a.i./ha) gave similar yields to cypermethrin (30 g a.i./ha) irrespective of the spraying techniques (Electrodyn, knapsack and ULV). The new application techniques have more potential for small-scale cotton farmers in developing countries as they receive limited training on the dilution of insecticides with water and calibration of knapsack sprayers.