| The effects of temperatures on weevils (Noechetina sp.) were studied at six constant temperatures. In the range from 15 to 30 , the lower the temperature was, the larger the developmental rate was. The distance between development times of egg and larva stage got shorter and shorter following the growth of the temperature. The developmental thresholds and effective constant temperatures of egg and larva were 8.68 and 148.24 day-degree, 8.62 and 611.79 day-degree, respectively. The optimum temperature of water surface for pupa development was 20~25 , when water surface temperature was above 30 , weevils could not complete the development of pupa stage.The fertilizer conditions of water hyacinth has directly effects on weevils reproductive capacity. The weevil larva feeding on water hyacinth sprayed with solution of nitrogenous (N) fertilizer was highest at the survival rate, ones feeding on water hyacinth sprayed with solution of phosphorus(P)fertilizer was lower than the former, ones feeding on water hyacinth sprayed with solution of potassium ( K. fertilizer was lowest. It was N that was favorable to the length and density of water hyacinth. The result of cluster based on scores of principal component showed the order of help to water hyacinth upgrowth: 1%, 3%, 10%P>0.5%N, 10%P>7%P, 5%K, 8%K 11%K. Water hyacinth treated with N, P was rich in organic compound. It was propitious to the development and reproduction of weevils, feeding quantity of weevils feeding on the water hyacinth treated with K decreased because of water hyacinth resistance to insects enhancing. So the survival rate of larva was low. Water hyacinth used for multiplication of weevils indoors should be fertilized with N largely, adding N in proper proportion together with a small quantity of K.Mature, healthy water hyacinth is Superior host to developing plants or declining plants. The number of weevils inhabiting in declining plants was very small. Feeding quantity of weevils is correlative negatively to water hyacinth leaf age, the equation is Y=21.2217-0.5460X (R2=0.9254 ) (Y= Feeding quantity, X= leaf age) . Weevils prefer feeding young leaves. The quantity of adult frass is larger feeding on young leaves than older leaves. Theleaves ranging in age from 1 to 20 day can be classed 3 groups based on the numbers of feeding scars and quantity of adult frass. 5~7 d leaves belong to mass feeding leaves category with high utilization rate.The relationship between sum of eggs and adult density was parabola. Eggs per female decreased following adult density increasing. The minimal room per couple weevils was upwards of 349.96cm3. Breeding weevils per couple in one cage was the perfect method to obtain eggs as many as could.Chemistry control was carried out where weevils were released, the herbicide drove weevils to disperse to adjacent no-spraying herbicide area. On the other hand, the death of a mass of water hyacinth made weevils move to safe area more quickly. It was not observed that Paraquat (ZENECA Ltd.) was toxic to weevils in field experiment. Under conditions of selecting optimum type, dosage, spraying methods and time, the integrated management is feasible.
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