Studies On Some Terrestrial Gastropods Injurious To Field Crops At Sharkia Governorate

This work is an attempt to obtain basic information concerning ecology, biology and control of some terrestrial gastropods populated field crops at Sharkia Governorate. Ecological studies revealed that six species belonging to three families of order: Stylommtophora were identified on field crops. Infestation with these species was obviously increased in the last few years at Sharkia Governorate. On the other hand, Frequency occurrence and population density of land gastropods infesting field crops were differed from district to another and from host plant to another also. Population density of Monacha cartusiana was markedly increased during spring months as compared to low or moderate values during autumn and winter months. Moreover, this snail can be considered as a seedling pest of cotton. Since, individuals of such snail move from infested clover fields to neighbouring cotton onces.Feeding of M. cartusiana on leaves of broad bean, Egyptian clover, cabbage, lettuce and pea, under laboratory conditions, significantly influenced total numbers of eggs and clutches as well as clutches size. The highest values were detected with lettuce and cabbage whereas few eggs were laid when snails were fed on leaves of pea. On the other hand, field experiments showed that snails of M. cartusiana aestivated during summer months under plants grown in the irrigation canals. Sugarcane was the most preferable one followed by elephant grass while bermuda grass was the least one in this respect. The majority of snails were seen with epiphragm during June, July and August, while in December all aestivated snails became active and moved from aestivation sites to the adjacent clover fields. The breeding season of M. cartusiana lasted three months starting from mid-November to mid-February. More clutches were laid during November and December as compared to low numbers during January and February. Clutch size tended to increase in the beginning of egg-laying period, but showed noticeable decrease in its second half. It ranged between 8 to 41 eggs/clutch with mean value of 22.31 eggs/clutch.Sharkia.