Brazilian researchers discover resistance of Helicoverpa armigera to pyrethroids

“One of the factors for the pyrethroid resistance in Brazilian populations of Helicoverpa armigera is the high frequency of the cytochrome P450 CYP337B3 gene,” said a statement from the Brazilian Committee of Actions against the Resistance of Insecticides. 

 

The committee belongs to an arm of the Global Federation of Plant Protection, an organization recognized by the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO).

 

The pyrethroids (Group 3A) are modulators of sodium channels on the cell that provoke repetitive transmissions and uncontrolled nerve impulses, hyperexcitability, loss of locomotor posture, paralysis and death. The pyrethroid resistance was reported in countries that from where the Helicoverpa armigera originated, such as India, China, Pakistan, and Australia, and in most cases it is related to the insecticide detoxification through the action of enzymes that have the capacity of metabolizing the molecule.

 

Researchers from the Luiz de Queiroz College of Agriculture (ESALQ) characterize the susceptibility of the Brazilian populations of H. armigera for two pyrethroids (deltamethrin and fenvalerate). After working with the synergists (PBO, DEF and DEM), they estimated the frequency of the resistance gene CYP337B3 belong to the monooxygenases group of the cychrome P450.

 

“The results show that even after using the highest dose of the applications of insecticides, the populations of H. armigera had a mortality rate lower than 50%. When the caterpillars are treated with the synergist PBO (inhibitor of the P450 enzymes) combined with the diagnosed dose of the specific insecticide the mortality rate of all populations was 100%. In addition, all populations presented the CYP337B3 gene with frequency above 0.95,” IRAC-BR pointed out.

 

“The results prove the importance of the implementation of resistance management strategies to preserve the effectiveness of chemical product, retard the selection procedure of resistant individuals in a population, control a plague and maintain it at tolerable levels below the threshold of economic damage. To manage it successfully, it is crucial to adopt the detection and monitoring programs of resistance of plague populations in the field to guide producers for the rational use of insecticides,” the experts concluded.