By Antynet Ford

Beatrice Mwende  was spraying her chilli farm again this week. The leaves had turned silver and streaked, and tiny pests were running across the soft tissue. But even with repeated spraying, the results were disheartening.

“They affect every crop,” said Beatrice, who grows and exports fruit and vegetables through her firm, Chilliexpo Consult Limited. “Even my chilli leaves are currently affected as the spray is taking place today.”

Thrips are tiny, fast-moving insects with fingered wings that have become a major threat to Kenya’s horticulture, wiping out up to 60 per cent of yields in some crops, according to studies. They have also become one of the hardest pests to control, with key insecticides now banned, and growing resistance reported to the remaining chemicals still allowed in Kenya, as the infestations get sharply worse as a result of climate change.

In Embu County, 2025 data from 11 to 27 per cent of banana farms infested, while a study of onion farms in   Kirinyaga found every farm surveyed was infested. They similarly have been found infesting French beans and many other crops, with the rising threat is being driven by climate change. 

Thrips populations drop during heavy rains, which knock down or drown larvae, but rise sharply in hot, dry conditions. With Kenya now experiencing rising temperatures and more erratic rainfall, researchers warn that climate change is increasing the number of thrips generations per year and spreading the pests further via wind and trade routes.

But Beatrice said the pests are often misdiagnosed in the early stages, delaying action and allowing the infestation to worsen.

“Thrips are difficult to detect because they are very small in size (around 2 mm in length), their light coloured bodies blend with plant tissues and hide and feed on flower buds, folded leaves, soft plant tissues, where they are well protected which makes it difficult to spot them with naked eyes, especially during early infestation,” she said. “Sometimes their early symptoms on crops, such as silvering or light streaks on leaves and fruits, can be mistaken for nutrient deficiency, leading to misdiagnosis.”

They are also quick to flee.

“Thrips are also quick movers; they fly fast, escaping detection when disturbed.”

First recorded in Kenya in the 1960s, thrips have now become a leading cause of losses for farmers and exporters alike.

“Thrips are a threat to both farmers and exporters due to the losses they can cause. Delayed detection can lead to heavy thrips infestation that is difficult and expensive to control, and its ability to transmit viruses can lead to irreversible crop loss,” said Beatrice.

Some species, such as the Melon Thrips (Thrips palmi), are quarantine pests. If detected in consignments headed to the EU, they lead to total interception.

“This becomes a total loss to an exporter and to some extent can cost him or her suspension of the export licence,” said Beatrice.

Yet chemical control is faltering. One of the key insecticides used against thrips, Pymetrozine, was banned this year by the Kenyan government. The remaining allowed insecticides, such as spinosyns (spinosad and spinetoram), abamectin, and pyrethroids, are all facing confirmed or probable resistance issues globally.

Spinosyn resistance has already emerged in greenhouse thrips populations in Spain and Australia. Resistance to abamectin has been documented in several thrips species. Pyrethroids are even more vulnerable, with overuse leading to widespread resistance and the added risk of disrupting the predators that keep thrips in check.

Beatrice said many Kenyan farmers continue to rely on these insecticides alone, despite their declining effectiveness.

“Currently, farmers are using a combination of biological, chemical, cultural, and physical methods to manage the pest. The efficacy of the method used varies greatly depending on how appropriately they are implemented based on findings. However, most farmers rely heavily on the use of insecticides without proper consideration of other integrated pest management strategies, hence reducing the long-term control effectiveness.”

She added that even with growing awareness, large gaps remain.

“From my experience, most farmers and extension officers are aware of thrips, but still, there are significant gaps in effective control methods and correct detection and identification of thrips species, especially where the symptoms mimic those of nutrient deficiencies,” she said. “There is over-reliance on chemical control methods by farmers that has led to repeated use of the same chemical molecules, leading to resistance and poor control. In some areas, farmers experience inconsistent extension support, especially those in remote areas.”

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In response, research institutions, including CABI and ICIPE, have begun developing non-chemical solutions. These include early detection tools, breeding of resistant plant varieties, use of natural enemies such as Orius bugs, predatory mites like Amblyseius swirskii, and entomopathogenic fungi such as Beauveria bassiana.

Sticky traps, fine mesh netting, silver reflective mulches, neem oil, chilli-garlic sprays, and crop rotation are among the growing toolkit of options now being promoted as part of integrated pest management.

Beatrice said the long-term outlook depends on whether farmers can adopt these integrated methods before thrips resistance renders the remaining insecticides ineffective.

“Species dominance is evolving, particularly F. schultzei, now leading in banana systems. Though there are no confirmed quarantine thrips in EPZs, there needs to be keen vigilance,” she said.

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