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<\/div>Cockroaches are a common pest<\/p>\n
LELACHANOK\/Shutterstock<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
People buying insecticide sprays to battle cockroaches are wasting their money as the insects have grown resistant to a key ingredient, sparking a call for US regulators to toughen up product testing rules.<\/p>\n
About 30 different cockroach species live among humans, but the German cockroach (Blattella germanica<\/em>), which is common throughout the world, is the one most likely to infest buildings. Previous studies<\/a> have demonstrated that it has developed widespread resistance to pyrethroid insecticides, which are commonly found in consumer products.<\/p>\n Now, Johnalyn Gordon<\/a> at the University of Florida and her colleagues have shown that while consumer sprays continue to work effectively on laboratory-sourced German cockroaches, bred from a line with no exposure to insecticides, they are ineffective against insects collected from real-world infestations.<\/p>\n The products are designed to be sprayed on to surfaces, killing the insects when they walk over the coating. But in the team\u2019s tests, coated surfaces killed fewer than 20 per cent of the collected cockroaches after exposure for 20 minutes. \u201cEven directly spraying them in an enclosed container with these products, we weren\u2019t getting 100 per cent mortality,\u201d says Gordon.<\/p>\n