Ecological 'resistance enhancement' of fruit growing against pests.

摘要

The threat to orchards and soft fruit plantations by the mass occurrence of pests and disease epiphytoses is escalating due to the increase in the area for monoculture, where the relationship between plant and pest or plant and pathogen is highly simplified. This creates a chance for the development of agrophages, particularly those with narrow range of hosts (e.g. codling moth [Cydia pomonella] and apple aphids, Venturia inaequalis causing apple scab, and Podosphaera leucotricha causing powdery mildew). The introduction of new high-yielding cultivars that are often devoid of resistance possessed by their progenitors enhances problems related to the health status of fruit production. Numerous studies proved that the biodiversity of habitats is one of the most important factors influencing the stability of species colonizing them. It is also well known that beneficial organisms, such as predators, parasitoids and antagonistic microorganisms, have important roles in the suppression of many pests. The enhancement of their populations can be achieved by providing a suitable environment for their development. However, in the modification of fruit agrocenoses, possible threats by infectious diseases, especially those caused by polyphagous bacteria and viruses, should also be taken into account. The increasing wild hosts of such pathogens can serve as a potential infection source. A good example is Erwinia amylovora, the causal agent of fire blight, which infects more than 130 plant species, including apple and pear. In plant communities, changes in temperature and humidity can be favourable for the development of diseases.