By Felix Ochieng Akech

Kisii tea farmer Vincent Okinyi is reporting his worst pest infestations in years, losing as much as 10% of his tea as he grapples with a red crevice mite flare up after using pyrethroids on his crops.

“The pests have reduced the number of good leaves I can pluck,” said Vincent Okiyni from Sameta. “I’m seeing browning and curled leaves, and I end up discarding a lot of flushes. My overall yield is down by over 10% compared to last season.”

For years, Vincent used synthetic pyrethroid Karate to prevent the mites, But mites are a type of spider and pyrethroids kill insects. They can deter mites, but can make infestations worse after several years of use, by killing the mites’ natural predators and leaving mites’ eggs uncontrolled.

For Vincent, the impression that the pyrethroid was stopping the mites blew up this year.

“Before, one spray was enough to control mites. But now the same chemical doesn’t work for long, so I find myself spraying almost every week. The pests return very fast,” he said.

In fact, his fall has been made worse by a common issue in mite control, This year, he started using propargite Omite. This is a purpose-built pesticide for mits, but only kills those that it can reach and that have hatched, it does not kill their eggs.

“Even after spraying, the mites remain on the leaves. Before, they would die within 2–3 days. Now the leaves still look damaged and new shoots are still attacked,” he said,

For farmers suffering from a post-pyrethroid mite flare up, agronomists advise swing a miticide in up to three sprays at close intervals to reduce new egg laying.

For Vincent, the eggs his spraying has not killed have been hatching and his mite population and the eggs it lays have been re-establishing between each spraying. He has also been alternating Karate and Omite, where Karate cannot control a heavy infestation and can increase it, while Omite is not killing the eggs.

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“I used to buy 1 litre for the whole season. Now I’m buying chemicals almost every two weeks. It is becoming very expensive.”

Vincent is one of millions of farmers getting little or no guidance in the ideal pest control for his crops. A KTDA agronomist advised him in training that it was better to alternate pesticides to avoid pest resistance, but he has received no advice on pyrethroids exacerbating mites, or on the need to control eggs as well as the mites themselves.

“I need guidance on the right chemical rotation, correct timing, and maybe access to more affordable but effective pesticides. Otherwise the cost will be too high,” he said.

Almost no research has been done on the cost to Africa’s smallholders in extra pesticide spend and additional crop losses from using the wrong pesticides and using the right ones incorrectly.