General effect of climate change on insects

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

2. 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

3. Climate change will also reduce the effectiveness of-
Host plant resistance,
Transgenic plants,
Natural enemies,
Biopesticides,
Synthetic chemicals for
pest management
introduction…

4. Higher temperatures and longer growing seasons
could result in increased pest population
Pest infestations often corresponds with changes in
climatic conditions
Such 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 pests
A 2.4 to 2.7-fold increase in pesticide use by 2050
introduction…

5.  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…

6. Increased temperature
 Insects are stenotherms (cold-blooded), sensitive to
temperature
 Higher temperature increase rates of development and
with less time between generations
20C temperature increase insects experience one to five
additional life cycles per season
Eg. Cabbage maggot, Onion maggot, European corn
borer, Colorado potato beetle

7.  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…

8. 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

9.  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…

10. These tritrophic interactions are affected by
climatic changes in diverse ways
natural enemy…

11. Effect of Changing Precipitation on
Insects
 Precipitation whether optimal, excessive or insufficient
 Key variable that affects crop-pest interactions
 Warmer environment has a tendency to hold more
water, it results in more intense and frequent rainfalls
 Small body-sized insects may be physically dislodged from the
host plant by heavy rainfall
 Often more of a problem during dry seasons when the
mortality factor is missing

12.  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…

13. 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…

14.  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 populations
Eg. Wet northern California
winter, the fungal pathogen
(Pandora neoaphidis) causes
catastrophic mortality
to pea aphid
precipitation on insects…

15. CO2 would increase canopy size and density of
plants
Produce high biomass and microclimates may
become more conducive for foliar pathogens
Eg. Rusts, Mildews, Leaf spots and Blights
Effect of Rising CO2 on Insects

16.  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 ratio
Insects respond to this ratio by increasing their feeding in
order to fulfill their metabolic needs for nitrogen
effect of rising co2 on insects…

17. Climate change on Pollination
Climate change impact pollination by altering-
The geographic ranges
Plant phenologies
Daily activity patterns of their pollinators
Mutualistic interactions

18. 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

19. Interactions among factors
Disease
Triangle
Environment
Climate change
Temperature
CO2
Precipitation
Pathogen change
Genetic shift
Movement
Host change
Variety
Cultural practice
Chemical practice

20. THANK YOU...