Susceptibility of the spider Theridion impressum to 17 pesticides

Susceptibility of immature individuals of the spider Theridion impressum to 17 pesticides (6 insecticides, 4 acaricides, 4 fungicides and 3 herbicides) was tested in the laboratory. The pesticides were applied at recommended rates in a Potter tower. Mortality was evaluated for 4 subsequent days. Broad-spectrum insecticides, cypermethrin+chlorpyrofos (Nurelle), -cypermethrin (Vaztak), and deltamethrin (Decis), were toxic to spiders. Selective insecticides, pirimicarb (Pirimor), Bacillus thuringiensis (Novodor), and triazamate (Aztec), were harmless. All tested acaricides, pirimiphos-methyl (Actellic), flufenoxuron (Cascade), -fluvalinate+thiometon (Mavrik), and bifenthrin (Talstar) showed high toxicity. Of the fungicides, dithianon (Delan), benomyl (Fundazol), iprodione (Rovral), and dodine (Syllit), only dithianon was slightly harmful, while the remaining fungicides were harmful. All herbicides, metazachlor (Butisan), clomazone (Command), and clopyralid (Lontrel), were harmless to T. impressum. Three selective insecticides, 3 fungicides and 3 herbicides are recommended for use in plant protection.