Diamondback Moth Resistance to Several Synthetic Pyrethroids

Most field strains of Plutella xylostella (L.) in Taiwan developed resistance to the four major synthetic pyrethroids—permethrin, cypermethrin, decamethrin, and fenvalerate—and the resistance levels to the three α-cyano 3-phenoxybenzyl esters were generally higher than that to permethrin. A diazinon-resistant strain showed significant cross resistance to all four compounds, whereas a methomyl-resistant strain had slight, yet consistent negative cross resistance to these compounds, except fenvalerate. Synergism of pyrethroid toxicity by piperonyl butoxide, but not DEF, was observed against a highly resistant strain. Fenvalerate resistance in the diamondback moth lacked sex linkage and was partially recessive and due to more than one gene.