Pyrethroids are commonly used. This widespread use of pyrethroids and DDT has caused Knockdown resistance (kdr) mutations. Almost no research has been done on the fitness implications. studies by Kumar et al., 2009 on deltamethrin in India, Plernsub et al., 2013 on permethrin in Thailand, by Jaramillo-O et al., 2014 on λ-cyhalothrin in Colombia, by Alvarez-Gonzalez et al., 2017 on deltamethrin in Venezuela, are all substantially confounded. As of 2019, understanding of selective pressure under withdrawal of insecticide is hence limited.
