مصطفی خنامانی

Climate change may affect plant-herbivore interactions and their associated ecosystem functions. Bio-control efficiency for weed control will be influenced by alteration in climate due to change in the development, morphology and reproduction of target pest. Bio-control agents being living micro-organisms and insects are sensitive to the climatic extremes like heat, cold, wind and rains. Precipitation changes can also affect predators, parasites and pathogens of weeds resulting in a complex dynamics. Changes in temperature can influence production of plant defense compounds against plant herbivores. It is known that levels of many insect-resistance allelochemicals increase during drought. For example, an increase in temperature may enable biological control agents from subtropical areas to survive on weeds in more temperate regions. Under changing climate, pathogenic fungi might be either benefitted by prolonged humidity conditions or significantly reduced by drier conditions. Direct effect of CO2 would also be related to changes in the ratio of C: N and alterations in the feeding habits and growth rate of herbivores, warming could also result in increased over wintering of insect populations and changes in their potential range. Some biological control agents invade roots and thereby stunting plant growth. Various bacteria harbour on root surfaces and excrete toxins thus reducing stunt root growth. Different fungi infect roots and obstruct the water transport system, which reduces leaf growth beneficial insects and nematodes feed directly on the weed roots causing injury which allows bacteria and fungi to penetrate.