Rise in Temperature & Pest Infestation

Climate change could have positive, negative or no impact on individual plant diseases, but with increased temperatures and humidity many pathogens are predicted to increase in severity. The most likely impact of climate change will be felt in three areas: in losses from plant diseases, in the efficacy of disease management strategies and in the geographical distribution of plant diseases.

Models on plant diseases indicate that climate change could alter stages and rates of development of certain pathogens, modify host resistance, and result in changes in the physiology of host-pathogen interactions. The most likely consequences are shifts in the geographical distribution of host & pathogen and increased crop losses, caused in part by changes in the efficacy of control strategies. Altered wind patterns may change the spread of bacteria and fungi that are the agents of wind-borne plant diseases.

Gradual increase in temperature conditions is usually more favourable for the proliferation of pests. Longer growing seasons like the spring, summer, and autumn may enable a number of pest species to complete a greater number of reproductive cycles during these warmer climates. Warmer winter temperatures may also allow larvae to winter-over in areas where they are now limited by cold, thus causing greater infestation during the following crop season. Pests will generally become more abundant as temperatures increase, through a number of inter-related processes such as range extensions & phenological changes, as well as increased rates of population development, growth, migration and over-wintering. Migrant pests are expected to respond more quickly to climate change than plants and may be able to colonise over newly available crops/ habitats.

The possible increases in pest and disease infestations has brought through the greater use of chemical pesticides to control them, a situation that enhanced production costs and also increased health hazards to environmental problems associated with agro-chemical use.

Of course, this may not be the case with farmers who follows the diversified cropping pattern that inhibit the process of pest build up either because one crop may be planted as a diversionary host, protecting other, more susceptible or more economically valuable crops from serious damage or because crops grown simultaneously enhance the abundance of predators and parasites which provide biological suppression of pest densities (Altieri and Nicholls 2004).