محمد خانجانی
نورعلی رجبی مظهر
طیبه حسینی

Biology of Iranian leaf gall mite (Eriophyes tristriatus Nalepa) was studied during 1997-2000. The leaf gall mite of walnut appeared at the lower leaves of the trees crown. It was developed into the median and upper parts of tree crown in moderately. Maximum densities were of the pest appeared in the early September. Pest damage of the leaves were observed mostly on the young trees or on leaves which is branches of with low diameter. The leaf gall mite overwintred as a deutogyn form into scales buds leaves and male organs. The felt leaves are not source of infestation in the later time or next year. The mite is distributed and transported by insects and wind. The average of infestation was 18% and also the rate of efficiency of natural enemies was 17.6%. At the moment many insects and mites are regarded as its main natural enemies in Hamadan. In this study a new species, Tydeus caryae Khanjani & Ueckermann is recorded and reported for the first time in world. Key words: Persian walnut, Leaf gall mite, biology, natural enemies, control..