Yogesh Wagh 2015-21-013

Plant Physiology

Long Term and Short Term Projection of Climate Change on Crop Pest Interaction

Introduction Changes in climate may trigger changes in-

Geographical distribution, Increased overwintering, Changes in population growth rates, Increases in the number of generations,Changes in crop-pest synchrony, Changes in interspecific interactions, Pest biotypes, Activity and abundance of natural enemies, Species extinction, Increased risk of invasion by migrant pests and efficacy of crop

protection technologies

Climate change will also reduce the effectiveness of-Host plant resistance, Transgenic plants, Natural enemies, Biopesticides, Synthetic chemicals for

pest management

introduction…

Higher temperatures and longer growing seasons could result in increased pest population

Pest infestations often corresponds with changes in climatic conditionsSuch as early or late rains, drought, or increases in humidity,

which can reduce yields

Climate change have increased pesticide use due to presence of diseases and pestsA 2.4 to 2.7-fold increase in pesticide use by 2050

introduction…

Insects are poikilothermic animals A poikilotherm : Is an organism whose internal

temperature varies considerably

They are highly sensitive to their surrounding climate particularly the temperature

introduction…

Increased temperature Insects are stenotherms (cold-blooded), sensitive to

temperature

Higher temperature increase rates of development and with less time between generations20C temperature increase insects experience one to five

additional life cycles per seasonEg. Cabbage maggot, Onion maggot, European corn

borer, Colorado potato beetle

Warmer winters -Reduce winterkill and consequently induce increased insect

populations It cause delay in onset and early summer may lead to faster

termination of diapauses in insects

Reproductive rate- Rising temperatures will lengthen the breeding season and

increase the reproductive rate raise the total number of insects attacking a crop and

subsequently increase crop losses

increased temperature…

Natural enemy

Parasitoids depend on a series of adaptations to the ecology and physiology of their hosts

According to a survey of over 1700 species, 50% of these wild species are already affected

Even a mid-range climate warming scenario predicts that 15% to 37% of the species may become extinct by 2050

Parasitism could be reduced if host populations emerge and pass through vulnerable life stages before parasitoids emerge

The tritrophic interactions between plants, herbivorous insects, and their natural enemies (predators, parasitoids, and pathogens)

Coevolutionary process specific to a particular environment and relatively stable climatic conditions

natural enemy…

These tritrophic interactions are affected by climatic changes in diverse ways

natural enemy…

Effect of Changing Precipitation onInsects

Precipitation whether optimal, excessive or insufficientKey variable that affects crop-pest interactions

Warmer environment has a tendency to hold more water, it results in more intense and frequent rainfallsSmall body-sized insects may be physically dislodged from the

host plant by heavy rainfallOften more of a problem during dry seasons when the

mortality factor is missing

Drought stress sometimes brings increased insect pest outbreaks

Drought can change the physiology of host species, leading to changes in the insects that feed on them

Cool, wet conditions can also bring on severe insect infestations, although excessive soil moisture may drown out soil-residing insects

precipitation on insects…

Increase in the frequency of flooding of fields could tend to suppress some soil dwelling insect populations

Eg. cranberry fruit worm and other cranberry insect pests

precipitation on insects…

Most fungi which are known to cause various diseases in insects (entomopathogens)

Fungal pathogens of insects are favoured by high humidity Lengthen periods of high humidity and reducing insect pest

populationsEg. Wet northern California

winter, the fungal pathogen (Pandora neoaphidis) causes catastrophic mortality to pea aphid

precipitation on insects…

CO2 would increase canopy size and density of plants

Produce high biomass and microclimates may become more conducive for foliar pathogensEg. Rusts, Mildews, Leaf spots and Blights

Effect of Rising CO2 on Insects

Insect pests could occur through indirect effects on host biochemical composition i.e. Increased simple sugars in the leaves

Greenhouse and lab studies have shown that high CO2 atmosphere increase C:N ratioInsects respond to this ratio by increasing their feeding in

order to fulfill their metabolic needs for nitrogen

effect of rising co2 on insects…

Climate change on Pollination Climate change impact pollination by altering-

The geographic ranges Plant phenologiesDaily activity patterns of their pollinators Mutualistic interactions

Miscellaneous Certain pesticides like Pyrethroids, Organophosphates

and especially the Biopesticides being highly thermo unstable degrade faster at higher temperature

These products to be less or not effective in pest control, necessitating frequent insecticide applications for effective control

Transgenic crops

Interactions among factors

Host

Disease Triangle

Pathogen

Environment Climate change

Temperature CO2

Precipitation

Pathogen change Genetic shiftMovement

Host change Variety

Cultural practice Chemical practice

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