This research was carried out in order to study the effect of repellency of the insecticide deltamethrin against the lesser grain borer, Rhyzopertha dominica (F.). Four strains of R. dominica were used: two of them were deltamethrin resistant, BR6 and BR12, and two were susceptible, BR4 and UK1. The insects were collected in storage units and maintained in laboratory. One hundred insects were released in the bottom of a plastic pot containing untreated wheat grain connected to another pot of same size containing wheat grain treated with LC5, LC25, LC50, separately, for each strain, replicated four times. The pots were kept horizontally in order to let the insects to move freely between the two compartments, at 25±1ºC and 60±5% of temperature and relative humidity, respectively. The assessment of insect distribution in the pots was performed 12 days after the releasing. The insects avoided the treated grain at all concentrations, meaning that the insecticide presents an effect of repellency against the insects. Nevertheless, there were no significant differences in the number of individuals of the susceptible strains between the treatments and the control. On the other hand, the resistant strains showed higher response to deltamethrin than the susceptible insects, especially at higher concentrations. The study of such behavior is fundamental for decision making in resistance management programs of stored product insects.
Behavior; Insecta; lesser grain borer; resistance; stored grains
