Environment plays an important role in development of plant diseases. It may affect succulence, any plant growth level, presence or even genetics of the plant.
Similarly, there is an absolute involvement of climatic factors to effect spore formation, multiplication, growth, survival, spread and spore germination as well.
Moreover, activity and production rate of the pathogen vectors may also be affected. A great climate change occurred in recent few years due to a lot of reasons. Global warming is the major cause of this climatic change.
Unexpected climate change is greatly affecting plant diseases directly and indirectly by promoting disease causing agents and insects population as well. Early changes in temperature and other factors favor the disease pathogens and their vectors to survive and infect the plants at initial stage when they are more susceptible for the attack.
Plant resistance mechanism is also going to affect drastically leading to promote the pathogens to spread diseases. In this way resistant plants are going to be susceptible for the pathogen attack.
In results, crop production is going to decline badly and there is massive reduction in market value of the fruits vegetables and other agriculture commodities. There are some biotic and abiotic factors favoured by the climate change.
- FUNGAL DISEASES
Gradual increase in CO₂ amount may increase or decrease in disease development ratio. Its increased amount positively affects plant canopy and density which favors different plant diseases. Also, it affects fungal activity in two ways.
Firstly, its varying amount has effect on stomatal opening and plants’ defence system which makes plants sensitive for the fungal attack. In other way, with the increased in CO₂, fungal activity and life cycle becomes rapid as in case of Erysiphi graminis the rate of attack becomes double in plants.
Increased temperature in environment causes plant injuries, which invite fungus to get entry in plant cells and cause infection e.g increase in plant blight. Storms and rains due to environmental changes affect plant structure system which makes faster growth in pathogens’ life cycle.
- VIRAL DISEASES
Fungi is the most studied pathogen influencing by the climate change. Viral infections have been ignored in aspect of climatic change, but it is greatly influenced and causes more disease spread comparatively. Increasing rate of CO₂ helps in spread of virus.
Viral transmission in plants is usually done by the insects e.g cotton leaf curl in cotton plant by whitefly. With the climate change insect reproduction rate is favored and rapid spread of viral diseases occurs. Other environmental factors e.g storms, hailing, high and low temperature etc cause plant injuries which through which virus takes entry into the plant system causing infection.
- BACTERIAL DISEASE
Bacterial activity is also affected positively by the climate change. These germs complete their life cycle in dead plant matter and gain entry in plants through insects or through stomatal openings causing different plant disease.
They need moisture for their best survival and infection. On increase in temperature their population decline is expected. However, bacteria mostly enter in the plant body through cuts and injuries. In summer storms there are more chances of plant injuries and direct effect on plant diseases by the increasing rate of bacterial infections.
- NEMATODAL DISEASES
Nematodes are soil living organisms. They spend more of their life period in damped shady soil. They basically attack on plants’ root portion and ultimately weakens the plant by nutrition deficiency as they feed and destruct the root structure e.g citrus trees.
Their reproduction rate and spread has direct relation with temperature. As temperature is increasing day by day so there is great threat to spread plant diseases by the nematodes.
- ABIOTIC FACTORS
Abiotic factors (temperature, humidity, storms, rain etc) affect plants in both direct and indirect way. Increased temperature causes injuries, plant burnings, wilting, blistering, discoloration and desiccation of the plant tissues etc while sudden decrease in temperature cause frost killing of plant parts e.g in cherry and peach. Low temperature also has negative effect on indoor plants.
However, they indirectly promote plant disease by favoring pathogens to reproduce rapidly and giving best suited environment for their survival and spread. Inadequate oxygen availability also affects plant growth by causing desiccation of different plant roots in specific soils. light, air pollution, acid rain and hailing also going to promote in these drastic conditions which also participate in plant destruction.
Activity of biological control agents is seriously affected by the change in climatic factors. Because change in temperature affects hibernating population in their off season and their activity badly affected due to unfavorable conditions in their active season.
Temperature changes and rains affects pesticidal activity. Due to which there is improper pest management. This gap also helps to produce new races of the pest population which are more dangerous and resistant against chemical control.
Human activities are the main reason for these circumstances. Fossil fuels burning is participating in increasing level of CO₂ in atmosphere. Aerosols and greenhouse gases are leading to global warming. Urbanization and industrialization is also the basic reason for such environmental changes.
These swear changes in environment also have negative impact on human health as well. The Agriculture economy of the country may be affected badly in future if such climatic changes neglected.
So, it is strictly needed that avoid all those activities on earth which participate in such climatic changes. Otherwise changes in temperature, rain water evaporation (increase in moisture level) and extreme conditions are expected to enhance plant disease epidemics in future.
Authors: Aamer Sohail1, Muhammad Waqas1, Muhammad Sufian1, Adeel Arshad2
1.Department of Entomology, University of Agriculture Faisalabad
2.Institute of Animal and dairy Sciences, University of Agriculture Faisalabad