We analyse the planetary perihelion precession and the deffection of light in the Schwarzschild field modified by a conical defect. By using observational results from solar system tests of general relativity, we obtain limits on the conical defect parameter <img src="http:/img/fbpe/bjp/v30n2/ses.gif">. For the physical case of a cosmic string the quoted limits are one and three orders weaker than the cosmological bounds.