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Agriculture, the heartbeat of the country’s economy and an essential industry for human survival, is under the silent threat of nematodes, a largely less-understood pest despite the significant economic losses it causes.

Danny Coyne, a researcher in tropical crop systems and Co-Leader of NemAfrica, shed light on the silent threat nematodes pose and the urgent need for awareness and action.

According to Danny, the big problem is that because we can’t see it, we ignore it.

“It’s easy to ignore something that you cannot see. The reality is nematodes affect every single crop and damage them to a huge extent,” he says.

“Estimates vary and are probably inaccurate, but we’re talking probably upwards of $150 billion a year in crop losses, basically,” he adds.

This often goes unaddressed because there’s a lot of mystery around nematodes and nematology.

“And partly that’s because there are very few nematologists,” said Danny.

NemAfrica, a joint nematology laboratory between the International Institute of Tropical Agriculture (IITA) and the International Centre of Insect Physiology and Ecology (ICIPE), is one of very few units that focus on nematodes and nematology and is the largest group in Africa, outside of South Africa.

Understanding Nematodes

Nematodes are tiny, worm-like creatures found almost everywhere: in the soil, water (fresh and salt), and even inside plants and humans. There are free-living nematodes, animal parasitic nematodes, insect parasitic nematodes and plant parasitic nematodes.

In agriculture, plant-parasitic nematodes are wreaking havoc by invading plants, mostly roots but not limited to.

“When nematodes attack crops, they weaken the plant, stunt its growth and make it vulnerable to other diseases. This subsequently results in low yields.”

Despite not given much attention by farmers, nematodes attack the roots, stem, and foliar, using a sharp, need-like structure called stylet to pierce the plant tissues and suck out nutrients.

“Among the root nematodes is the ectoparasite. From outside, in the soil, it feeds into the root, but it does not enter the root,” said Danny.

Then, there are the endoparasites that live inside the root, and they migrate.

“Root-knot nematodes are a type of endoparasite,” said Danny.

Foliar nematodes infect the leaves, stems, and buds of plants rather than the roots.

Symptoms and Damage

“Root nematodes are a tricky pest as we only realize the damage that they cause in tuber crops during harvest because the root is the product of the crop,” said Danny.

Root-knot nematodes cause the cracking of potatoes.

“When you see the rotting of sweet potato or carrots or beetroot, what has happened is that nematodes have caused damage and rotting takes over thereafter. This reduces, if not completely restricts, the crop’s ability to take up nutrients and water.”

Stem nematodes cause deformations and unpleasant flower heads and stems. When they attack the leaves, they may reduce the chlorophyll content and the ability to photosynthesize, as well as deform the leaves and fruits in fruit-bearing plants.

The loss associated with nematodes runs in billions. According to Danny, Nematodes and mealybugs are “about the two major problems on pineapple, and companies like Del Monte spend a huge amount of money each year on fumigating their soils against nematodes.”

The Importance of Diagnostics

“When you’re sending your samples to a crop diagnostic clinic, you need to know what your problem is, or you need to send everything,” says Danny.

He further highlights that if a farmer’s crop is affected by a foliate nematode, it’s no good sending soil. You need to send the leaves.

“And if you’ve got a problem with your roots, you need to send your roots as well as the soil because it’ll depend on the type of nematode.”

Danny highlighted that doing the correct diagnostics will guide the formulation of sustainable solutions. He further emphasized that partnerships with relevant stakeholders are important in tackling the threat of nematodes.

“NemAfrica and Del Monte are currently collaborating to come up with more sustainable practices to manage nematodes. There need to be more productive partnerships across the industry to tackle the problem.”

Besides crop rotation, planting crops resistant to nematodes is also an effective management practice.

“However, you need to have your farm analyzed to know which type of nematode you’ve got in order that that hybrid-resistant variety is suitable for the problem you have,” said Danny. “Resistance is there; use it, but don’t abuse it,” he cautioned.

Despite nematodes being invisible, they have a devastating effect on agriculture, putting food systems and the economy in jeopardy.

Consequently, more awareness should be created to inform farmers on the diagnostics to address this problem.

Moreover, collaboration among industry stakeholders is also crucial to address the hidden crisis beneath our feet to better protect our crops.

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