title: Chemical control of Loxosceles intermedia (Araneae: Sicariidae) with pyrethroids: field and laboratory evaluation.
abstract: Bites from the recluse or brown spiders (genus Loxosceles) can cause necrotic lesions and systemic effects in humans throughout the world. In the state of Paraná, Brazil, loxoscelism is considered a serious public health problem, and Loxosceles intermedia Mello-Leitão (Araneae: Sicariidae) is associated with the majority of reported accidents. In the present research we evaluated the susceptibility of L. intermedia to pyrethroid insecticides currently used for the control of spiders in both field and laboratory conditions. In laboratory tests, the most active pesticides in descending order were microencapsulated lambda-cyhalothrin (LC50 = 0.023 mg/kg), nonmicroencapsulated lambda-cyhalothrin (LC50 = 0.047 mg/kg), deltamethrin (LC50 = 0.26 mg/kg), and cypermethrin (LC50 = 1.38 mg/kg). Cockroaches, Phoetalia circumvagans (Burmeister) (n = 30), killed with microencapsulated lambdacyalothrin, were offered to the spiders. L. intermedia fed on 63.3% of the dead cockroaches during the first 6 h of experiment; none of the spiders died during the subsequent 15 d. Microencapsulated lambdacyalothrin was chosen for application in two contiguous houses. The mean volume applied was 22.8 mg (AI)/m2. Dead spiders were found during all the inspections up to 60 d after the initial application. In total, 297 dead spiders were collected; 65.7% in the attic shared by the two homes, 10.8% inside the house that had most cracks and crevices sealed and 23.6% in the control house. The use of lambda-cyhalothrin-based products for L. intermedia control is discussed.
authors.affiliation: Departamento de Zoologia, Laboratório de Entomologia Médica e Veterinária, Universidade Federal do Paraná, Caixa Postal 19020, CEP 81531-980 Curitiba, PR, Brazil.
authors.forename: M A
authors.initials: MA
authors.lastname: Navarro-Silva
authors.forename: J E L
authors.initials: JE
authors.lastname: Duque
authors.forename: E N
authors.initials: EN
authors.lastname: Ramires
authors.forename: C F S
authors.initials: CF
authors.lastname: Andrade
authors.forename: E
authors.initials: E
authors.lastname: Marques-da-Silva
authors.forename: F A
authors.initials: FA
authors.lastname: Marques
authors.forename: C E
authors.initials: CE
authors.lastname: Delay
authors.forename: J D
authors.initials: JD
authors.lastname: Fontana
authors.forename: A C S
authors.initials: AC
authors.lastname: Silva
authors.forename: G M
authors.initials: GM
authors.lastname: Fraguas
mesh_terms: D000818:Animals; D007300:Insect Control; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D011722:Pyrethrins / Q000494:pharmacology*; D013112:Spiders / Q000187:drug effects*
chemical_list: D007306:Insecticides; D011722:Pyrethrins