Pesticide Effectiveness in Africa: Why Armyworm Control Is Moving Toward Integrated Pest Management

Pest control in African agriculture is changing.

For maize, sorghum, rice and pasture growers, the traditional question has often been: Which insecticide should I use?

Today, a more important question is emerging:

Why can the same insecticide produce different levels of field control depending on pest stage, application timing, local conditions and resistance?

Recent African armyworm (Spodoptera exempta) outbreaks in southern Africa, together with continuing pressure from fall armyworm (Spodoptera frugiperda), highlight why pesticide effectiveness cannot be evaluated by active ingredient or concentration alone.

Effective pest management increasingly depends on a combination of:

Monitoring + Early Intervention + Correct Pesticide Use + Biological Control + Resistance Management + IPM

Recent African Armyworm Outbreaks Highlight a Changing Pest-Control Challenge

African armyworm (Spodoptera exempta) is an important migratory pest in sub-Saharan Africa.

According to South Africa's Agricultural Research Council (ARC), African armyworm primarily attacks grasses and cereal crops. During outbreaks, large populations of larvae can develop rapidly and cause severe defoliation.

African armyworm should not be confused with fall armyworm. Although both belong to the genus Spodoptera, they are different species with different biology, behavior and management considerations.

Recent outbreaks in southern Africa have renewed attention on how these pests should be managed and whether conventional insecticide programs alone can provide sustainable long-term control.

Researchers have also investigated naturally occurring pathogens of African armyworm, creating new opportunities for biological control research.

One recent area of interest involves the entomopathogenic fungus Metarhizium rileyi, which has been observed infecting African armyworm larvae.

However, this should not yet be interpreted as a commercially proven replacement for conventional crop protection products. Further research and field validation are necessary before such approaches can be widely adopted.

Why Can Insecticide Performance Decline in the Field?

When growers say that a pesticide "doesn't work like it used to," poor product quality is only one possible explanation.

Actual pesticide performance is influenced by many factors, including:

• Pest species

• Larval development stage

• Application timing

• Active ingredient selection

• Spray coverage

• Application rate

• Temperature and rainfall

• Crop growth stage

• Previous pesticide use

• Insecticide resistance

One particularly important factor is pest development stage.

Smaller, younger larvae are often easier to manage than larger, more developed larvae. Once caterpillars become larger or move into protected feeding locations, effective control can become more difficult.

This means:

An effective insecticide does not necessarily provide the same level of control at every pest stage.

Applying the correct product too late may therefore produce disappointing results even when the active ingredient itself remains effective.

Fall Armyworm Remains a Major Challenge for African Maize

While African armyworm can cause serious outbreaks, fall armyworm (Spodoptera frugiperda) represents another major and persistent crop protection challenge.

Native to tropical and subtropical regions of the Americas, fall armyworm was first reported in West Africa in 2016 and subsequently spread rapidly across much of sub-Saharan Africa.

Maize is one of its most important host crops in Africa.

The Food and Agriculture Organization of the United Nations (FAO) has developed extensive guidance for managing fall armyworm in African maize production systems, emphasizing Integrated Pest Management rather than dependence on a single control method.

How Much Damage Can Fall Armyworm Cause?

CABI conducted an important assessment of the potential impact of fall armyworm on maize production in Africa.

The assessment estimated that, without control measures, fall armyworm could potentially cause annual maize losses of approximately:

8.3–20.6 million tonnes

across 12 major maize-producing countries in Africa.

This was estimated to represent approximately:

21%–53% of the three-year average annual maize production considered in the assessment.

The estimated economic value of these potential losses was approximately:

US$2.48–6.19 billion per year.

These figures should be interpreted carefully.

They represent estimated potential losses under the conditions and assumptions of the CABI assessment. They do not mean that Africa currently loses exactly 20.6 million tonnes of maize every year to fall armyworm.

Nevertheless, the estimates demonstrate the potential scale of the pest and explain why fall armyworm management has become an important food-security and crop-protection issue.

Why Is Chemical Control Alone Not Enough?

Chemical insecticides remain an important pest-management tool when they are locally registered, appropriately selected and correctly applied.

However, relying exclusively on chemical control creates several challenges.

These include:

Insecticide resistance, effects on beneficial organisms, environmental risks, application costs and inconsistent control when treatments are poorly timed.

FAO therefore promotes Integrated Pest Management (IPM) for fall armyworm.

An IPM program may combine:

• Field scouting and monitoring

• Correct pest identification

• Early intervention

• Good agricultural practices

• Conservation of natural enemies

• Biological control

• Appropriate biopesticides

• Responsible use of registered insecticides

• Insecticide resistance management

The objective is not necessarily to eliminate chemical insecticides.

Instead, the objective is to use them more effectively and only when appropriate within a broader pest-management strategy.

Natural Enemies Are Part of Africa's Pest-Control System

African agricultural ecosystems already contain many organisms capable of attacking important crop pests.

Research on fall armyworm in Africa has identified parasitoids, predators and entomopathogens associated with the pest.

These beneficial organisms can contribute to natural pest suppression.

This creates an important consideration for pesticide programs.

Repeated and indiscriminate use of broad-spectrum insecticides may affect not only the target pest but also beneficial insects and other natural enemies.

A poorly designed program can therefore create a cycle:

Pest outbreak → Repeated broad-spectrum spraying → Reduced natural enemies → Greater dependence on insecticides

Integrated pest management attempts to avoid this cycle by combining chemical and non-chemical approaches.

How Does Insecticide Resistance Affect Pesticide Effectiveness?

Insecticide resistance is another important reason why field performance can change over time.

When pest populations are repeatedly exposed to insecticides with the same mode of action, susceptible individuals are more likely to die while individuals with greater tolerance have a higher chance of surviving and reproducing.

Over multiple generations, this selection pressure can reduce the susceptibility of the pest population.

Simply increasing the application rate is not an appropriate resistance-management strategy.

A better approach is to:

1. Correctly identify the target pest.

2. Determine the pest's development stage.

3. Select a locally registered product appropriate for the crop and pest.

4. Apply the product at the correct timing and label rate.

5. Achieve adequate spray coverage.

6. Avoid unnecessary repeated applications.

7. Rotate appropriate insecticide modes of action according to local guidance.

8. Integrate chemical treatments with other IPM practices.

Biological Control Is Becoming More Important

Biological control is receiving increasing attention in African armyworm and fall armyworm management.

For African armyworm, researchers have investigated biological agents including Spodoptera exempta nucleopolyhedrovirus (SpexNPV).

Naturally occurring fungal pathogens are another area of research.

For fall armyworm, CABI and other agricultural research organizations have investigated biological control agents, biopesticides, natural enemies and agroecological management approaches.

This does not mean biological products will completely replace conventional insecticides.

A more realistic future pest-management model is:

Chemical Control + Biological Control + Monitoring + Resistance Management

The appropriate balance will depend on the pest, crop, infestation level, local environment and regulatory requirements.

How Should Buyers Evaluate Pesticide Effectiveness?

For pesticide importers, distributors and large growers in Africa, comparing products only by concentration and price is increasingly insufficient.

A professional crop-protection decision should answer at least five questions.

1. What Is the Target Pest?

African armyworm, fall armyworm, aphids, whiteflies and mites have different biological characteristics.

The product must match the target pest.

2. What Stage Is the Pest At?

Young and mature larvae may respond differently to treatment.

Application timing can therefore be just as important as product selection.

3. What Is the Mode of Action?

Buyers should look beyond brand names and concentrations.

Understanding the active ingredient and its mode-of-action group is important for building an effective resistance-management program.

4. How Will the Product Be Applied?

Even an effective active ingredient may perform poorly if spray coverage is inadequate, application timing is incorrect or unfavorable weather occurs around treatment.

Application technology is part of pesticide effectiveness.

5. Is the Product Registered Locally?

Africa is not a single pesticide-registration market.

Countries including Kenya, Nigeria, Ghana, Tanzania, Zambia and South Africa have their own regulatory systems and registration requirements.

Products should therefore be used only according to applicable local registrations and approved labels, including permitted crops, target pests, application rates, safety requirements and pre-harvest intervals.

Africa's Pesticide Market Is Moving From Products to Solutions

Armyworm management illustrates a broader trend in crop protection.

Professional agricultural customers increasingly need more than a bottle of insecticide.

They need:

The right pest identification + The right active ingredient + The right pest stage + The right application timing + The right application method

This has important implications for pesticide manufacturers and exporters.

In the past, purchasing decisions might have focused heavily on questions such as:

What is the price? What is the concentration? What is the minimum order quantity?

Those questions remain important, but professional buyers increasingly also need to know:

Which pest does this product control? When should it be applied? Why might field performance decline? How should different modes of action be rotated?

Technical support, resistance-management knowledge and practical crop-protection guidance can therefore become increasingly important parts of a supplier's value.

Conclusion

Recent African armyworm outbreaks and continuing fall armyworm pressure demonstrate that pesticide effectiveness cannot be evaluated by active ingredient concentration alone.

Pest species, larval stage, application timing, spray coverage, weather, resistance and natural enemies can all influence field performance.

CABI's assessment estimated that, without control measures, fall armyworm had the potential to cause approximately 8.3–20.6 million tonnes of annual maize losses across 12 major African maize-producing countries.

The challenge therefore requires more than simply searching for a "stronger pesticide."

A more sustainable approach is:

Early Detection → Correct Identification → Timely Intervention → Biological Control → Responsible Pesticide Use → Resistance Management → Continuous Monitoring

For Africa's crop-protection industry, the future of pesticide effectiveness is increasingly about applying the right solution to the right pest at the right time.

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Authoritative References

1. Fall Armyworm: Impacts and Implications for Africa
CABI

2. Integrated Management of the Fall Armyworm on Maize: A Guide for Farmer Field Schools in Africa
Food and Agriculture Organization of the United Nations (FAO)

3. African Armyworm – Spodoptera exempta
Agricultural Research Council (ARC), South Africa

4. Managing African Armyworm Outbreaks in Sub-Saharan Africa: Current Strategies and Future Directions
Insects, 2025, 16(6), 645
Peer-reviewed scientific review

5. Fall Armyworm Programme
CABI