In a webinar hosted by CropLife SA in September, farmers were cautioned to implement good stewardship practices to prevent tomato leaf miner (Tuta absoluta) from developing resistance against pesticides.
Tuta absoluta is a highly destructive pest in South Africa, affecting mostly tomato crops and causing up to 100% crop losses. Since tomatoes are a key crop for food security and income generation, the pest presents a major challenge to local producers. Speaking during the webinar, Hamish Ramanand, stewardship specialist at CropLife SA, said there were no tomato varieties that were resistant to the pest, and that since registered crop protection chemicals were limited, farmers needed to be mindful to rotate active ingredients to prevent chemical resistance.
He clarified that, despite many reports from producers that chemicals were ineffective, there was no evidence that T. absoluta had become resistant to pesticides.
"Incidents where there was no knock-down effect after applying pesticides were found to be a result of incorrect applications and dosages. It is therefore critical that farmers follow the correct dosage rates and regularly calibrate spray equipment to ensure it is functioning properly," Ramanand explained. However, he noted that sensitivity shifts had been observed, which meant the knock-down effect was reduced after applying pesticides. This was because of overapplication of the same active ingredients, as well as improper applications.
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