Resistance to insecticides in the TYLCV vector, Bemisia tabaci

The whitefly Bemisia tabaci (Gennadius) is a serious pest of many agricultural crops (Byrne & Bellows, 1991). It is relatively new as an economic pest and has raised to increasingly higher levels of importance over the last 20-30 years in many semiarid and arid production areas. This coincided with the appearance and dispersion of the B biotype of B. tabaci showing distinct biochemical and host range characteristics (Costa & Brown, 1991). The B biotype was proposed as a distinct species, B. argentifolii (Perring et al., 1993; Perring, 2001) but the definition of B. tabaci as a complex of biotypes or races is more generally accepted (Brown et al., 1995; De Barro et al., 2005). The two most widespread and damaging biotypes that attack tomatoes are the B and Q biotypes. The B biotype has a broad geographical distribution and is considered to be a recent invader over much of its range. The Q biotype was originally considered to be restricted to the Iberian Peninsula, but has recently been detected in southern Europe and Middle East as well in the Far East and in the USA (e.g., Horowitz et al., 2003a; Zhang et al., 2005; Zanic et al., 2005; Dennehy et al., 2005). Although some natural biological control has been achieved, the use of insecticides remains the primary means of control for many crops. In tomatoes, insecticides are applied against B. tabaci especially to prevent transmission of tomato yellow leaf curl virus (TYLCV).