DEVELOPMENT, REPRODUCTION AND SURVIVAL OF MONONYCHELLUS-TANAJOA (BONDAR) (ACARI, TETRANYCHIDAE) ON CASSAVA GROWN UNDER SOILS OF DIFFERENT LEVELS OF NITROGEN

The effect of different levels of nitrogen on the development and repr oduction of Mononychellus tanajoa (Bondar) (Acari: Tetranychidae) was evaluated in greenhouse and laboratory studies using a range of soils with different levels of nitrogen concentration. The effect was evalua ted for M. tanajoa reared for up to three generations. Experimental tr eatments included cassava leaves from plants grown in soils from three representative field sites in southern Benin and cassava leaves from plants grown in soil fertilized with different rates of nitrogen in th e form of urea (46% nitrogen). There were no significant changes in re lation to soil and, thus, to leaf nitrogen in developmental rates, pre -oviposition periods, longevity and egg production of M. tanajoa reare d in either group of soils (untreated and fertilized) after three gene rations. However, M. tanajoa population densities were significantly m ore abundant on leaves of plants grown in soils with moderate levels o f added nitrogen fertilizer compared to plants with either no or a hig h levels of added nitrogen fertilizer during this same period. Our res ults are compared to those predicted by a simulation model of M. tanaj oa population dynamics in relation to soil and leaf nitrogen and discu ssed in terms of the rates of nitrogen applied, differences in host-pl ant conditions between greenhouse and laboratory and field studies and in terms of relationships between nitrogen and other nutrients.