PEST CONTROL | PPC103 MAY 2021

Effects of climate change are touching every living form on earth, including humans.

Dr Partho Dhang, the author of ‘Urban Pest Control: A Practitioner’s Guide’, explores how this generation’s most significant threat will likely change how we control and eradicate pest species in the UK.

SPEED VIEW:

• With a 2°C temperature increase, insects might experience one to five additional life cycles per season
• Warmer summers and milder winter temperatures favour mosquito development and extend the biting season
• Fly populations could increase substantially,
• with increases of up to 244% by 2080
• Temperature has shown a negative effect on synthetic pyrethroids
• Shift to insecticide baits, physical barriers, pest proofing, traps, and monitors are greener choices the pest control business could move into to mitigate climate change.

Earth’s global mean surface temperatures have risen by 0.74°C ± 0.18°C when estimated by a linear trend over the last 100 years, and the rate of warming over the previous 50 years is almost double that in the last 100 years (IPCC, 2007).

Climate change and urban pests

The topic of climate change and urban insect pests has been recently reviewed by Dhang (2017).

This review was part of a series by the Centre for Agriculture and Bioscience International (CABI), Wallingford UK, to address many topics relating to climate change. This included strategies to develop sustainable systems that minimise the impact on climate or mitigate the effects of human activity on climate change (CABI, 2021).

Urban ecosystems are rich in resources and contain excess food, water and shelter for urban pests to thrive.

However, one element which has a significant influence on the life of these pests is temperature.

Insects are cold-blooded organisms and cannot regulate their body temperatures. The temperature of their bodies is approximately the same as that of their immediate environment.

Therefore, the temperature is probably the single most important environmental factor influencing pest behaviour, distribution, development, survival, and reproduction (Petzoldt and Seaman, 2010).

It could be safely assumed that the influence of temperature on insects largely overwhelms all other environmental factors (Bale et al. 2002).

Based on this, it has been estimated that with a 2°C temperature increase, insects might experience one to five additional life cycles per season (Yamamura & Kiritani, 1998).

Moreover, in the absence of predators and competitors in urban environments, pests can attain extremely high densities if unchecked. Such high populations have been brought to light on numerous occasions during catastrophic events such as natural disasters like earthquakes and tsunamis.

Putrefying organic debris, inundation and large-scale breakdown of urban sanitation largely contribute to outbreaks of flies, mosquitoes and rodents (Srinivasan, 2006; CIEH, 2008; Lee 2012).

The Chartered Institute of Environmental Health (CIEH) predicted in 2008 that warmer summers and milder winter temperatures favour mosquito development and extend the biting season.

It also predicted wetter winters will provide more temporary and underground aquatic sites for some species during winter and spring.

Models produced for houseflies, Musca domestica, and blowflies, Calliphora sp. showed predictions based on climatic factors were strongly correlated, suggesting that fly population changes are primarily driven by the weather rather than biotic factors (Goulson, 2005).

These models predict that under likely scenarios of climate change in the UK, fly populations could increase substantially, with increases of up to 244% by 2080 compared to current levels (Goulson, 2005). Further prolonged warmth and warmer conditions to cooler zones will help establish fly populations and expand distribution.

Many other pests are also expected to be influenced by changes in the environment brought about by climate change, specifically non-vectors and nuisance pests inhabiting and frequenting urban areas.

Roy et al (2009) undertook an interesting study to determine the effect of climate change on nuisance insect species in the UK. The report highlights a list of insect pests that will or will not be influenced by climate warming (see next page).

Climate change and pesticides

The efficacy of a pesticide is determined by its active ingredient. However, various chemical and physical properties of pesticide, such as stability, vaporisation, penetration and degradation, depend on temperature.

A literature review shows that the effect of pesticide is rapid on insects at higher temperatures, although they do not always show a linear relationship with temperature (Uddin and Ara, 2006).

Temperature has shown a positive effect on organochlorine, organophosphate and carbamates in general but has shown a negative impact on synthetic pyrethroids (Uddin and Ara, 2006; Weng and Shen, 2007).

A few studies have made an effort to evaluate the effectiveness of pesticide with relevance to climate change. In summary, it has been shown that climate change could significantly affect the efficacy of pesticides and alter the result of a pest control activity through temperature changes.

Pyrethroid and organophosphate insecticides show sensitivity to temperature; pyrethroids have a negative and organophosphates, a positive temperature coefficient, respectively (Musser and Shelton (2005).

However, some studies also revealed variation in the toxicity within a given insecticide class (Muturi et al 2011, and Scott, 1995) between insect species and temperature range tested (Muturi et al 2011).

Therefore, generalisation of the temperature-toxicity trend could be misleading within a given class and for different insect species (Khan and Akram, 2014).

In addition to the direct impact of temperature on insecticide efficacy, the temperature can also influence many tools and methodologies that make use of them.

For example, insecticide-treated nets (ITN), long-lasting insecticidal nets (LLIN), residual insecticide treatment (IRS), and odour-baited traps all rely on pesticides working in warm environments.

It can be safely concluded that climate change and resulting temperature regimens, in particular, will have a profound influence on urban pests and their management strategies.

Climate change and health of pest managers

Climate expert Grahame Madge, at the UK’s Meteorological Office, told the BBC that, while weather variations occurred naturally, the world was about one degree warmer than pre-industrial levels and, as a result, extreme weather was becoming more likely.

Heatwaves are not uncommon, but according to weather experts, they are amplified by a rise in global temperatures and are likely to become more frequent. This is one of the more predictable impacts of our warming climate (BBC 2019).

Pest managers regularly work outdoors and will be directly exposed to the weather components of a warming climate (Sims and Appel, 2014).

Climate change will make it more difficult and expensive for pest control managers to insure their businesses or other valuable assets, particularly in risk-prone areas.

Insurance is the primary means used to protect a business against weather-related disasters. Climate change will increase the frequency and intensity of extreme weather events.

These changes are likely to increase property losses and cause costly disruptions to operations. Escalating losses in many areas have already affected insurance availability and affordability (Sims and Appel, 2014).

Climate change and the business of pest control

Pest control is a fossil fuel-driven business. One kilogram of an emulsion concentrate (EC) formulation contains between 500-900g of a petrochemical solvent.

It is packed in a plastic bottle which is a petroleum-derived product and then shipped to a distant country using a ship that burns bunker fuel. Once received, the pest controller takes the product to a site miles from his office and potentially loads it in a stainless-steel fogging machine with a diesel diluent.

The entire process is carbon-intensive but continues as it is the least expensive option.

A greener way out would be to shift to a water-based formulation, use non-plastic packaging, make the product locally and use sprayers not made of petroleum derivatives.

A shift to insecticide baits, physical barriers, pest proofing, traps and monitors are certainly greener choices the pest control business could move into to mitigate climate change.

Conclusion

“When we have a fact-based view of climate change, we can see that we have some of the things we need to avoid a climate disaster, but not all of them.”

Bill Gates

During the pandemic and resulting lockdown, human activity was vastly curtailed, and it is now estimated that this phenomenon changed daily fossil CO2 emissions by -17% on a global scale (Corinne Le Quere, 2020). It is agreed that this has come at an economic and social cost.

Still, it opens up opportunities to set structural changes in companies and businesses for a low carbon work path.

Businesses can look into mechanisms that had sustained them during the pandemic as an example to take them forward. As an industry, we could do our part by considering:

• The calculated use of transportation
• Shift to EVs
• Automation
• Use of intelligent monitors
• Consolidated shipping
• Online meetings
• A shift from incentivising travel for staff and clients with other alternatives
• Giving a discount to clients who are into green technologies
• Putting savings in banks that fund earth-friendly technologies.

These measures will delay (if not stop) the perils caused by climate change.

In the words of Bill Gates, “When we have a fact-based view of climate change, we can see that we have some of the things we need to avoid a climate disaster, but not all of them.”

REFERENCES

Bale, JS, et al. Global Change Biology 8, pp. 1-16
BBC (2020). bbc.com/news/world-europe-48756480
CABI (2021). cabi.org/products-and-services/about-cabi-books/cabi-climate-change-series/
Chartered Institute of Environmental Health (2008). A CIEH Summary based on Urban Pests and their Public Health Significance. WHO Regional Office for Europe, Denmark
Corinne Le Quere (2020). nature.com/articles/s41558-020-0797-x
Dhang, P (2017). Climate change impact on urban pests. (Ed. Dhang, P.) CABI UK, pp 15-30
EPA (Dec 2020). epa.gov/ghgemissions/sources-greenhouse-gas-emissions
Gates, B (2021). time.com/5930098/bill-gates-climate-change/
Glunt, KD, et al (2014). Malaria Journal, 13, 350.
Goulson, D, et al (2005). Journal of Applied Ecology. 42, 795–804.
Henriques, (2021). theconversation.com/spiders-are-threatened-by-climate-change-and-even-the-biggest-arachnophobes-should-be-worried-122666
IPCC (2007). ipcc.ch/publications_and_data/ar4/wg2/en/ch6s6-es.html
Karen, AP et al (2012). Review of Panam Salud Publica 32, 212-214
Khan, HAA, Akram, W (2014). PLoS One 9
Lee, CY (2012). ipmcenters.org/ipmsymposium12/Plenary_Lee.pdf (accessed 15 September 2015)
Majekodunmi, A et al (2002). Journal of Environmental Health Research 1
Musser, FR, Shelton, AM (2005). Pest Management Science 61, 508–510
Muturi, EJ, et al (2011). Journal of Medical Entomology 48, 243–250
Petzoldt, C, Seaman, A (2010). umaine.edu/oxford/files/2012/01/III.2Insects.Pathogens1.pdf
Polson, KA, et al (2021). Acta Tropica 117, 31-38
Roy, H, et al (2009). nora.nerc.ac.uk/8332/
Rust, MK (1995). Oxford University Press, USA, pp 149-170
Scot, JG (1987). Bulletin of Entomological Research 77, pp 431-435
Sims, SR, Appel, AG (2017). In Climate change impact on urban pests (Ed. Dhang, P), pp 31-49
Srinivasan, R (2006). Journal of Medical Entomology 43, 631-3 researchgate.net/journal/0022-2585_Journal_of_Medical_Entomology
Uddin, MA, Ara, N (2006). Journal of Life Earth Science 1, 49-52
Valles, SM, et al (1998). Florida Entomologist 81, 193 researchgate.net/journal/0015-4040_Florida_Entomologist
Wang, XY, Shen, ZR (2007). Phytoparasitica 35, pp 414-422
Yamamura, K, Kiritani, K (1998). Applied Entomology and Zoology 33, 289- 298

Source: PPC103