Invasion of insect pests: Some nature-based solutions

Invasive species, whether plants or animals, are mostly non-native species. When introduced into an ecosystem, they quickly colonise a region, displacing native species with detrimental impacts on an entire ecosystem.


According to the Union for Conservation of Nature and Natural Resources (IUCN) and Davis (2009), Invasive pest species are major threats to agriculture, forestry, livelihood and human health with associated huge economic losses.

These insects could be introduced either intentionally or unintentionally into an ecosystem, but are able to adapt extremely fast, out-compete native pests and eventually even replace them.

An invasive species tends to thrive well in host locations because there are little or no threats in the ecosystem to check their population.

Again, controlling the population of invasive species is quite problematic because knowledge on treatments and control mechanisms is limited within the new territory invaded.

Their problematic nature has necessitated the use of chemicals for pest control, and caused the need for the awareness of their potential environmental impacts especially in natural or protected areas.

This awareness has influenced an evolution toward a more integrated pest management approach that includes the use of pesticides.


Among the over six million species of insect, only 20–30 are important pests for major crops. The key for a proper insect pest management is to understand their biological structure, behaviour, ecological impact, and engineer effective and efficient methods to either control or magnify such impacts on the environment to achieve a crop production system that optimises the use of natural resources, protects the environment, and maximises output in a sustainable way.

Insect pests are responsible for two major kinds of damage to growing crops. First is direct injury done to the plant by the feeding insect, which eats leaves or burrows in stems, fruit, or roots.

There are hundreds of pest species of this type, both in larvae and adults, among orthopterans, homopterans, heteropterans, coleopterans, lepidopterans, and dipterans.

The second type is indirect damage in which the insect itself does little or no harm but transmits a bacterial, viral, or fungal infection into a crop.

Examples include the viral diseases of sugar beets and potatoes, carried from plant to plant by aphids. Another indirect attack is the deposition of honeydew on plants that gives rise to sooty mould growth, which blocks light and air from the leaves and reduces photosynthetic productivity (Muniappan et al., 2009) Such significant pests and diseases include;

The Plague (Black plague)

This was one of the most devastating diseases in human history. This disease is caused by the bacterium Yersinia pestis and transmitted between animals and humans by contact with infected fleas.

The Plague resulted in the death of about 1/3 of the European population in the early 14th Century, when human’s homes and places of work were inhabited by flea-infested rats.

The main causal organism is the Rattus species. More than any other group of vertebrates, species of the genus Rattus have probably contributed a lot in incidents of widespread plague infestations both to humans through disease transmission and harm to food crops (Alpin et al. 2003).

It is surprising how the Rattus spp. is able to thrive in a diversified ecosystem across the globe even in the presence of diversified rodent population (Alpin et al. 2003). An invasive species’ ability to establish itself would typically be significantly hampered by the presence of numerous, well-established rivals, however Rattus species have not only succeeded in doing so but are also flourishing, notably in parts of northwest Uganda and other African countries including Ghana (Patterson, 1979).

Potato Late Blight

This disease was the most devastating and historically significant plant disease that destroyed potato crops in Europe in the 1840s leading to mass starvation.

One of the most significant effects of the disease on the population of the U.S. was the Great Irish Potato Famine from 1845 to 1847, where up to one million people died from the loss of their staple food crop, and nearly the same number of people emigrated to the rest of Europe and the U.S. to prevent starvation and death.

Late blight is caused by an oomycete or fungus-like microorganism, Phytophthora Infestans, which is a specialized pathogen of potato, tomato and other members of the solanaceous plant family.

The P. Infestans, according to Cooke et al., (2013), is known to have originated from Mexico and some western and central parts of Africa until the historical field invasion in Europe.

The Phytophthora is a genus with several species which are mostly pathogens causing a large range of damage on several plant and food crops (Frimpong et al., 2021).

Since the introduction of this species in Ghana, from Cameroon, it has been a major threat to food security in the country causing huge amounts of food loss and low yields.

Their effect according to Frimpong et al., (2021), is a challenge to attaining the UN sustainable development goals on hunger reduction and poverty alleviation because of the livelihood dependence on agriculture especially in Sub- Saharan Africa.

One major impact of the Phytophthora species is the Black pod disease, the most destructive known disease of cocoa worldwide caused by Phytophthora palmivora and P. megakarya  (Adomako et al., 2021). This disease has since its insurgence threatened cocoa production and the economic development of Ghana due to the immense contribution of cocoa to the nation’s GDP.

Aside Cocoa, the Phytophthora infection affects cocoyam leaves, avocado, pawpaw, pineapple and other arable crops in Ghana.


The issue of Invasive insect species becomes more alarming when it threatens human lives as in the case of the plunge of malaria and its widespread in Africa.

The recent spread of the new invasive Anopheles stephensi burdens effort made towards combating malaria in Africa (Ahmed et al., 2021).

According to the World Health Organization, approximately one million people die each year as a result of mosquito bite consequences (WHO, 2020).

Also, Okwa (2019) reported that the mosquito is the world’s lethal insect that spreads malaria, the most common cause of death worldwide.

Malaria remains the leading cause of outpatient visits, accounting for 40 per cent of all visits (Ameme et al., 2014), children under the age of five (5) and pregnant women are the most vulnerable groups (GHS, 2017).

Fall Armyworms attack

Fall Armyworm (FAW) a migratory insect pest known to be a major cause of maize destruction across most fields in America, their impact is increased under warm and humid circumstances.

The FAW’s ability to cause huge destruction lies in its ability to breed rapidly, migrate and infest a wide range of host plants (Assefa et al., 2019).

It emerged in Ghana evidently in 2017, and according to MOFA (2017), about 14,247 Ha of maize cultivated lands all over the country were destroyed.

This brought a major instability in Ghana’s economy due to dependence on maize in Ghana. Aside maize, Fall armyworm larvae wreak havoc on, rice, sorghum, millet, sugarcane, vegetable crops, cotton, and a variety of other crops (Assefa et al., 2019; Sisay et al., 2019a).

Evidently from a number of research studies, the fall armyworm’s arrival in Africa has caused widespread concerns (Davis et al., 2018).

Even before its great emergence in Ghana, the Fall armyworms devastated large fields in Benin, Nigeria and Togo in 2016 (Agboyi et al., 2020).

According to Ghana’s Ministry of Food and Agriculture (2017), millions of Cedis are believed to have gone into controlling and stabilising the havoc by this invasive insect species.

Harmful effects of Pesticides as a solution

Chemical insecticides or pesticides have been known to be the remedy for the general insect pest damage and therefore used as well to compact destructions posed by invasive insect pests.

Most African countries, especially Ethiopia, use pesticides such as pyrethroids, carbamates, and organophosphates (Gutirrez-Moreno et al., 2019).

The widely used chemical pesticide in Ghana is emamectin benzoate, which costs farmers on average US $22.0 per purchase, while lambda-cyhalothrin costs farmers on average US $6.51 per purchase.

After subtracting subsidies, emamectin benzoate cost US $28.0 and lambda-cyhalothrin cost US $12.3 (Rwomushana et al., 2018).

According to Owusu (2017), the PPRSD of the Ministry of Food and Agriculture (MOFA) has released a list of recommended pesticides (active ingredient) for Fall armyworm control, which include; Maltodextrin, Emamectin Benzoate+Acetamiprid, Emamectin Benzoate, Chlorpyrifos+Deltamethrin and Acetamiprid + Indoxacarb etc.

Chemical insecticides build up toxic residues in the food crop and the various environmental media such as land, water and air.

These toxic residues have the potential of travelling along the food chain, causing harm to the various organisms involved.

The user of these harmful pesticides is not left out as they cause respiratory problems such asthma and skin irritation.

The best solution to invasive insect pest’s damage

The best remedy to invasive pests’ damage is an award winning six (6) years extensive research work that has birthed a novel organic (plant-based) insecticide named WAH INSECTICIDE. This insecticide is proven and tested to be the best in spraying invasive insect pests.

WAH Insecticide has a high specificity aside their effectiveness in the control of insects. Thus, their use ensures the control of only the target insects leaving ecological important insects safe in their natural environment.

Aside from WAH Insecticide having a high specificity, target insects do not build up resistances to its treatments as it offers the best type of insecticidal action in controlling target insects for a longer period of time unlike their chemical competitors.

Mosquitoes (Culex spp. and Anopheles spp.), houseflies (Musca domestica) and black ants (Lasius niger) were used as test specimens for the novel insecticide prepared.

This insecticide yielded the best insecticidal property killing mosquitoes in an average time of 1.78 ± 0.45seconds, houseflies in 5.18 ± 0.43 seconds and black ants in 23.52 ± 0.54 seconds (Assifuah-Hasford et al., 2018)

A full-scale piloting test was organised on this insecticide using fall armyworms as target insects by a professor with the agronomy department of University for Development Studies (UDS).

Conclusions of research

Fall armyworm larval mortality was significantly reduced by the WAH insecticide product applied at the rate of 25 and 30 ml/15l compared to the untreated control.

Also, all the WAH insecticide treatments performed well above the control in reducing FAW damage incidence in maize; WAH treatments at 25ml/15l and 30ml/15l were as effective as Emastar@20ml/15l in protecting the maize crop from FAW damage.

WAH treatment at dosage above 25 ml/15l was however, found to show serious phytotoxicity symptoms on the treated plants

Eventually, there was a significant increment in maize grain yield due to the WAH insecticide treatment; an average yield increase of 150% over the control was obtained.

Due to the extensive research work done on this novel insecticide, it is no doubt to be the best organic insecticide for invasive insect pests’ damage, as it has no or less minimal effects on the environment and the user.

Also, it is less costly as compared to the chemical insecticides.

Hence, WAH INSECTICIDE can be used as a general insecticide in mosquito outdoor spraying, spraying of invasive insect pests on agricultural farms and outdoor spraying of household insect pests.


The havoc caused by invasive insect pests can be overwhelming, but if appropriate measures are not taken in dealing with them, ecosystem services would be affected.

Aside from the endangerment of the environment in the use of insecticides, human health is at stake, nature-based solutions (NbS) present an effective and efficient opportunity to combat the issues on invasive insect pests and at the same time safeguard the environment.

It is recommended that the Government provides incentives, encourages the production and use of organic insecticides, and the law-making body of the country should enact a LI or an act to govern the production and use of organic insecticides.

There is also a huge opportunity for the youth to capacitate themselves and research innovative ways of solving the problem of species invasion especially concerning food security and climate stability.

Using NbS to address food destruction by insect pests is an avenue to scale up research on natural insecticides and translate it into production and use on-field, to expand Green jobs.

By Elizabeth Dwamena-Asare & Priscilla Nyamekye Appiah

Source: GNA

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