If you think you might be dealing with a pesticide resistant population, applying higher concentrations of the same pesticide generally won’t give better control. Once a pest population is resistant, the mode of action, or how the pesticide controls the pest, is no longer effective or is considerably less effective. Generally, the levels of control needed for satisfactory effectiveness cannot be easily achieved if the same pesticide continues to be used.
Once you determine the group the product you have been using belongs to, begin to explore alternatives that fit in a different group. For example, if you believe your pest population may be resistant to deltamethrin, a pyrethroid that belongs to Group 3, don’t choose another pyrethroid, such as bifenthrin to attempt control. Instead, choose a pesticide from a different group such as an insect growth regulator from Group 7, or perhaps consider a bait product with yet a different Group’s active ingredient.
Selection for resistance to a specific chemical can be reduced by rotating chemicals – and not just chemicals but functional Groups and modes of action. However, to delay the evolution of resistance by several orders of magnitude compared to rotation, use a mixture or combination of pesticides at the same time. These mixtures or combinations work well because as pests are killed with a lethal dose of pesticide A in the mixture, they are simultaneously affected by pesticide B. Only the very rare individuals who have mechanisms of resistance to BOTH products can survive.
"Better management of pests often means better products are needed in the fight."
If you believe you are dealing with a pesticide resistant population, take the time to learn what “Group” the pesticide you have been using belongs to. Refer to this website for more information on pesticide groups.
Technical Services Manager PCO Product Development