Effect of whitefly on cotton productivity

The silverleaf whitefly (SLW) Bemisia tabaci strain 'B' (=B. argentifolii Bellows and Perring) has been a severe pest of numerous field and vegetable crops for many years. A better understanding of the complex interactions between the SLW and the host could serve as a basis for reducing the risk of high pest population buildup. The plant's influence on the insect's establishment and developomental success can be manifested in several ways, from signaling the insect where to land to facilitating proper feeding, oviposition and development to maturity (eg, Bernays and Chapman 1994). Previous experiments and observations conducted with cotton plants have shown that the plant physiological state, eg, water or mineral-nutrition status, may affect the level of SLW infestation (Mor, 1986; Bentz et al, 1995; Skinner, 1996); however the basis for this effect is not clear yet. Another unexplored aspect of the plant-SLW interaction is the mechanism via which the insect interferes with plant productivity. In tomato, feeding injury caused by SLW reduced leaf chlorophyll content, photosynthetic capacity and stomatal conductance (Buntin et al, 1993). A reduction in photosynthetic capacity caused by SLW has also been reported for cotton (Shtaynmetz, 1990; Yee et al, 1996). This study was aimed at investigating the effects of SLW on cotton productivity and their underlying physiological mechanisms.