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The space available to plants affects the available resources and hence modifies the growth habits and yield potential of plants. The effect of four seeding densities (250, 500, 750 and 1000 viable seeds/m2) and three row spacings (12, 15 and 20 cm) were evaluated at Morfa Mawr field station at the University of Wales, Aberystwyth, UK during the 1993 and 1994 growing seasons. Number of capsules per plant, number of seeds per capsule, thousand-seed weight and seed yield were examined during the study. Capsule index (CI) and harvest index (HI) were calculated from the observed data. During the first year, capsules per plant, seeds per capsule and capsule index were increased by decreasing the seed density, while the maximum seed yield of 3.9 t/ha was recorded at the highest seed density of 1000 seeds/m2. An increase in row spacing led to an almost linear increase in most of the yield attributes of the crop. During the second year, the response of yield and yield attributes to seeding densities was similar to that recorded during the first year. Seed yield increased with decreasing row spacing, while the rest of the components did not show any consistent response. During the first year, the overall performance and production of the crop was higher than in the second year because of the better weather conditions, with mild temperature and high rainfall during the season.

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The laelapid mites Cosmolaelaps keni and Laelaspis astronomicus beside the rhodacarid mite Protogamasellopsis denticus are biological control agents and being native predators in Egypt. In order to raise active population of above species, the biology and demographic parameters, of the three tested species were observed under laboratory conditions with eggs of Ephestia kuhniella. All predatory species were developed and reproduced with E. kuhniella eggs. The mean developmental and oviposistion periods of L. astronomicus females were the longest from the other tested species. The mean longevity of C. keni was longer than that of P. denticus. Cosmolaelaps keni consumed more E. kuhniella eggs during the oviposition and adult longevity periods than other species did. Protogamasellopsis denticus fed on E. kuhniella food gave the most rate of oviposition as shown by the maximum fertility, net reproductive rate and gross reproductive rate. Laelaspis astronomicus preying on E. kuhniella eggs gave the longest generation time, lowest rate of fecundity and all life table parameters compared to other tested species; therefore E. kuhniella eggs was appropriate for the oviposition of P. denticus and C. keni rather than L. astronomicus.

This study is the first to report that E. kuhniella eggs were an acceptable factitious food for P. denticus, L. astronomicus and C. keni.

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