Yam beetle infestations are causing serious problems for farmers in Nigeria, especially in the Middle Belt region, where yams are a major crop. Farmers in places like Benue, Nasarawa, and Kogi have reported yield losses of up to 50%.
These beetles burrow into yam tubers while they’re still growing, leaving damage that can’t be fixed and reducing both the quality and value of the yams. For example, in Gboko, Benue State, some farmers say they’ve been struggling to make ends meet because of these pests, losing much of their annual income.
Economic considerations of yam beetle infestations
Yam beetle infestations threaten not only individual farmers but also the country’s food security, as yam is a staple in Nigerian households. In Ebonyi and Enugu states, farmers report they can’t meet local demand because of the infestations. Meanwhile, exporters in Lagos face rejection rates of up to 20% for damaged yams, which is hurting Nigeria’s reputation in international markets.
Yam beetle infestations can lead to significant economic losses. In Oshimili North Local Government Area of Delta State, damage rates ranged from approximately 27.69% to 39.72%, with a mean beetle attack rate of 32.69%, causing substantial financial strain on small-scale farmers. Investing in effective pest management strategies is crucial to safeguard yields and ensure economic stability.
What makes yam beetles especially dangerous is that they attack tubers underground, so the damage often goes unnoticed until harvest. The beetles thrive in sandy soils, which are common in yam-growing regions (NRCRI, 2023).
Unfortunately, most farmers don’t have access to affordable pest control solutions. Research institutes like the National Root Crops Research Institute (NRCRI) are working to develop pest-resistant yam varieties and to teach farmers Integrated Pest Management (IPM) techniques. However, without more investment in things like affordable pesticides, awareness campaigns, and research, this problem is likely to persist.
Understanding the threat
Yam beetles are tricky pests. They live underground, feeding on yam tubers during the growing season. Farmers often don’t realise there’s a problem until harvest, by which time the damage is already done. Here’s a quick look at their lifecycle:
- Egg Stage: Eggs are laid in the soil.
- Larval Stage: Larvae feed on organic matter in the soil.
- Adult Stage: Adult beetles feed directly on yam tubers, causing the most damage.
To combat these pests, farmers need to use a combination of methods. Below are six IPM strategies that are effective and practical for smallholder farmers in Nigeria.
6 Integrated Pest Management strategies for yam beetle control
Integrated Pest Management (IPM) is an approach that combines multiple methods to manage pests in an economically viable, environmentally friendly, and socially acceptable manner. It emphasises the use of biological, cultural, physical, and chemical methods in a coordinated way to reduce pest damage to an acceptable level without harming the ecosystem.
1. Cultural Practices
Cultural practices involve adjusting farming practices, which can disrupt the yam beetle’s lifecycle. These methods are often low-cost and easy to implement:
- Crop Rotation: Switching yams with non-host crops like maize, cassava, or groundnuts can prevent beetles from breeding continuously in the same soil. For example, some farmers in Benue and Nasarawa States have reported fewer beetles after two planting seasons of crop rotation.
- Timely Planting and Harvesting: Planting yams after the peak yam beetle season and harvesting early can minimise exposure. In Delta State, farmers who planted yams in April noticed fewer infestations compared to those who planted in March.
- Field Sanitation: Clearing and burning leftover crop residues can destroy beetle eggs and larvae hiding in the soil. Regular weeding also helps limit beetle habitats.
2. Chemical Control
Chemical pesticides, when used properly, can be effective against yam beetles.
- Treating Yam Setts: Farmers can treat Yam Setts with insecticides like chlorpyrifos or carbofuran before planting. Research in Ebonyi State found that treated setts had 40% fewer infestations compared to untreated ones.
- Soil Application: Applying insecticides like imidacloprid around the base of yam plants can protect tubers from beetles. Farms in Kogi State saw a 60% reduction in beetle damage using this method.
- Safety First: It’s important to follow safety guidelines when applying pesticides to avoid health risks and environmental harm. Extension workers often organize workshops to train farmers on safe pesticide use.
3. Resistant Yam Varieties
Growing pest-resistant yam varieties can reduce the impact of infestations.
- Choosing the Right Cultivars: Some yam species, like water yam (Dioscorea alata), are less attractive to beetles than white yam (Dioscorea rotundata). In Kwara State, trials with hybrid yam varieties showed promising results, with much less damage reported.
- Collaborating with Researchers: Farmers should work with research institutes like the International Institute of Tropical Agriculture (IITA) to access pest-resistant varieties.
4. Biological Control
Using natural enemies of the yam beetle is another sustainable solution.
- Encouraging Natural Predators: Certain ants and ground beetles feed on yam beetle larvae. Farmers can encourage these predators by avoiding broad pesticide use, which harms beneficial insects.
- Entomopathogenic Fungi: Fungi like Metarhizium anisopliae have shown promise in controlling yam beetles in lab studies. Field trials in Anambra State are testing their effectiveness.
- Intercropping: Planting yams alongside crops like cowpeas or pigeon peas can repel beetles, as these plants release chemicals that beetles dislike.
5. Mechanical and Physical Control
- Traps and Barriers: Light traps can attract and capture adult beetles, while trenches filled with sand or water around yam fields can act as barriers.
- Manual Removal: Regularly inspecting fields and removing beetles or larvae by hand is labour-intensive but effective for small-scale farms. Farmers in Cross River State reported better results by combining this with other strategies.
6. Monitoring and Early Detection
Monitoring yam fields can help catch infestations early.
- Soil Sampling: Checking soil periodically for beetle larvae can alert farmers before major damage occurs.
- Pheromone Traps: Although not widely available in Nigeria, pheromone traps can help track beetle populations, making it easier to time pest control efforts.
Conclusion
Tackling yam beetle infestations requires a mix of approaches tailored to local conditions. By combining cultural, chemical, biological, and mechanical methods, farmers can reduce losses and improve yields. Efforts like planting pest-resistant varieties, using eco-friendly biological controls, and staying vigilant through early monitoring will go a long way toward keeping yam beetles under control.
Farmers are encouraged to reach out to local agricultural extension officers or research institutes for advice on specific pest management solutions that suit their farms.
