There is currently a very favorable climate for biological control of pest weeds. Moreover, biological control plays a significant role in the Integrated Plant Protection Management. Traditional methods of weed control, such as cultivation and the use of herbicides are not practical or desirable for some stands of weeds, and biological control has become an attractive strategy for control of pest weeds. Control of Rumex confertus Willd. by natural enemies that reduce its density is the good example of utilizing biological control on the European and worldwide scale. The aim of the conducted studies was to evaluate the dynamic of population of Pegomya nigritarsis Ztt. (Diptera, Anthomyiidae) on Rumex confertus Willd. and to determine the impact of pest's injuries on the growth of a plant.

Weeds are harmful organisms connected with human activities; therefore there is a need for their control. human development and mobility have caused on purpose or purely incidental introduction of plants, exotic very often, to new sites and ecosystems. A dominating method of weed control is applying chemicals. However, chemical compounds are often of low selectivity, they also contaminate the environment and become ineffective quickly because of acquired resistance of treated organisms. The control of Rumex confertus Willd. and other weeds of the genus Rumex spp. is often not possible because of economical reasons. Large areas abundant in sorrel populations would require a large sum of money invested in expensive chemical control. Biological methods of weed control look far more promising solution to this problem. Rumex confer/us Willd. is a plant corresponding to criteria to qualify it as an object for biological regulation. The objective of the study was to evaluate dynamic of population and development of the insects of the genera Gastroidea spp. (Gastroidea viridula Deg. and Gasrroidea polygoni L.) occurring on Rumex confertus Willd.