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 reproduction 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 evaluated for M. tanajoa reared for up to three generations. Experimental treatments 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 the form of urea (46% nitrogen). There were no significant changes in relation to soil and, thus, to leaf nitrogen in developmental rates, pre-oviposition periods, longevity and egg production of M. tanajoa reared in either group of soils (untreated and fertilized) after three generations. However, M. tanajoa population densities were significantly more abundant on leaves of plants grown in soils with moderate levels of added nitrogen fertilizer compared to plants with either no or a high levels of added nitrogen fertilizer during this same period. Our results are compared to those predicted by a simulation model of M. tanajoa population dynamics in relation to soil and leaf nitrogen and discussed in terms of the rates of nitrogen applied, differences in host-plant conditions between greenhouse and laboratory and field studies and in terms of relationships between nitrogen and other nutrients.