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Beetle Hormones Creates Eco-friendly Pest Control

internationalisation Fellowship | 02/05/2016

Figure 1: The red flour beetle Tribolium castaneum is a devastating pest to stored grain products and has been for nearly 4000 years. Pseudo-coloured scanning electron micrograph. © Kenneth A. Halberg

This article explores the possibilities of turning insects’ own signalling molecules, hormones, against themselves in order to develop more effective, specific, and environmentally friendly tools for pest control.

By PhD Kenneth Agerlin Halberg, University of Glasgow

By the year 2050, the global population is expected to reach an estimated 10 billion people, which will require a 30% increase in current global food production compared to current levels. This needs to be accomplished while at the same time limiting agricultural land-use, environmental strain and CO2 emissions, and therefore we are faced with one of the 21st century’s grand challenges. At present, an estimated 20% of the total global food production is lost to insect attack, why new and more effective pest management strategies are an integral part of achieving this goal. In this research project, Dr Kenneth Agerlin Halberg, along with researchers from University of Glasgow, will explore the possibilities of turning insects’ own signalling molecules, hormones, against themselves in order to develop more effective, specific, and environmentally friendly tools for pest control. Specifically, Halberg and colleagues will focus on characterising the hormonal signalling associated salt and water balance in beetles, which due to their agricultural impact and number of species, represents a particularly attractive target. This information will ultimately be used to direct the synthesis of artificial hormones that may fatally disrupt water homeostasis in target pests, without interfering with humans or ‘beneficial’ insects. 

Why Insects? 

Insects are small animals of great importance. They represent the largest group of animals on Earth, and have colonised every part of the world inhabited by humans.There are more than one million species of insects described, with an estimated 30 million species in total. Despite their small size, they have a huge impact on people's lives. According to the World Health Organization (WHO), more than one million people die each year of vector-borne diseases like malaria and dengue fever, yet many more suffer as a result of lost food production caused by insect attack. Consequently, large amounts of insecticides are used annually to control insect pests worldwide. This approach, however, has selected for widespread resistance to current insecticides among harmful insects. Moreover, an increasing number of insecticides have been shown to be harmful to both humans and the environment. Therefore there is an urgent need to develop alternatives to traditional pest management strategies.

Figure 2: Pie chart illustrating the relative animal biodiversity of all animal groups. There are more insect species (light grey, outer circle) than all other animal groups combined (dark grey, outer circel). © Kenneth A. Halberg. 

New Strategies 

It is extremely difficult to develop insecticides that only target the insects harmful to plants and crops. Traditional insecticides are very unspecific, and a host of harmless and even beneficial insects are killed. Recently, the global death of honeybees, annually pollinating crops worth 150 billion US dollars, has been linked to the excessive use of insecticides. But perhaps the solution to these problems may be found in the insects themselves? Kenneth Agerlin Halberg explains: 

“Traditionally employed insecticides are neurotoxins that typically target the insect’ nervous system, and therefore do not distinguish between so-called 'damaging' and 'beneficial' insects. Ideally, new insecticides should therefore be able to specifically target the insect whose population we want to control, without impacting human health or the environment. By studying insect hormone systems (see fact box), we hope to learn how insects regulate different critical processes and how we may influence these systems by using synthetic, hormone-like substances to diminish specific insect populations."

Complex Signalling

Hormones are blood-borne, signalling molecules that act as molecular messengers between the brain and peripheral tissues. Hormones regulate key processes in all multicellular organisms and are critical for normal development, metabolism, reproduction, and behaviour. All of these processes can potentially be targeted to affect the survival of specific insects. However, the hormonal control of salt and water balance represents a particularly attractive target. 

“Insects are in almost constant danger of desiccation due to their small size. For a long time, we have therefore focused on how their kidney system regulates the salt and water balance of the insect. It turns out that the hormones that regulate kidney function are not the same in all species of insects, and that they typically possess small molecular variations. This gives us a good opportunity to work on how to selectively target certain species, and thereby better avoid ‘off-target effects’,” says Kenneth Agerlin Halberg.

Knowledge on how different insects control their salt and water balance is still very limited. This knowledge is essential to determine whether harmful insects, such as flour beetles and mosquitoes, possess unique hormone systems that can be targeted without harming humans or beneficial insects, such as honey bees. 

Method for mapping cells in the insect kidney, which receive the different hormonal signals (Modified from: Halberg et al. 2015 Nature Communications). 1. Synthetic insect hormone is attached to a fluorescent probe (chemical compound that re-emits light at specific wavelengths when excited by light). 2. The fluorescent hormone is applied to a dissected insect kidney. 3. The fluorescent hormone binds to its receptor. 4. Visualisation of the cells that receive the signal. Kenneth A. Halberg.

Kenneth Agerlin Halberg continues:“We have recently developed a novel method by which we can fast and efficiently map the cells in the insect's kidney that receive the hormonal signals (see "Want to Know More?"). This allows us to get an overview of which cells control the salt and water balance in different insects much faster and easier than before, and determine which signals they are sensitive to. This knowledge is essential – not only in order to understand basic insect physiology – but also to target and influence insect populations far better than we can today.”

Better Pest Control

In this research project, Kenneth Agerlin Halberg and his colleagues aim to characterise the hormonal signalling associated with salt and water balance in beetles. Constituting by far the largest group of insects, beetles are a particularly attractive target for pest control. Knowledge on beetle hormone systems will eventually be used to develop artificial, chemically stable insect hormones (hormone mimetics) that can be used to destabilise the insects’ ability to regulate their body fluid composition, and thereby introduce new, more specific and environmentally safe pest control. 

What It Means to Receive Funding from the Carlsberg Foundation 

“With support from the Carlsberg Foundation I am provided with the opportunity to work at Glasgow University in Scotland. It is the fourth oldest university in the English-speaking world, and one of the world’s highest-ranked universities, and can thus offer me an extraordinary environment for my research. At Glasgow University I will work with Professor Julian A.T. Dow, one of the world's leading researchers in the field of insect physiology and endocrinology (the study of hormones), who is in a unique position to give me the necessary support to my project,” says Kenneth Agerlin Halberg.