Impact Type: Direct exposure to pollutant
A number of sudies (Dohmen et al. 1984, Mansfield & Freer-Smith 1981) have shown that plants that had been fumigated with NO2 and SO2 were more prone to aphid attack, and that aphid productivity was higher as a result of changes in the amino acid composition of the plants. Some studies suggest that aphids grow faster under conditions of high NO2 and SO2 (Whittaker 1994, 2001). Other studies, where spruce trees were exposed to vehicle exhaust gases, have shown no effect on aphid performance (Viskari et al. 2000), and no significant effects on aphids were observed in a controlled fumigation of spruce and pine seedlings with NO2 (Holopainen et al.,1995).
Masters and McNeill (1996) suggest that it is difficult to predict how susceptible a particular variety of host plant will be to insect pests when stressed by pollution. They showed that plants that were normally resistant to aphid attack can become vulnerable when subjected to raised concentration of NO2. However, the reverse can also occur with normally highly susceptible plants becoming more resistant with raised levels of NO2. In healthy plant air pollutants are generally taken up diffusion through the stomata (Kersteins 1996), in addition to this the damage caused to the plant by insect feeding can itself significantly affect this uptake of pollutants (Whittaker 2001).
|Critical Load/ Level|
No estimate available