Integrated pest management

Not all insecticide resistance is created equal in green peach aphid

While neonicotinoid resistance has been detected in green peach aphid in Australia, you won’t experience complete control failures…yet.

In Australia, green peach aphid (Myzus persicae, GPA) is known to have resistance to four different chemical mode of action sub-groups – synthetic pyrethroids, organophosphates, carbamates, and now neonicotinoids.

But the type of resistance is not the same for each chemical, and this matters for control efficacy.

Two insecticide resistance mechanisms have been identified in Australian GPA populations: target-site resistance and metabolic resistance.

Target site resistance occurs when the site where the insecticide acts in the insect changes. This stops the insecticide binding or interacting at its site of action and as a result, reduces its efficacy or prevents it from working altogether.

In contrast when an insect population has acquired metabolic resistance, it is able to detoxify or destroy the insecticide more efficiently than susceptible populations.

In Australia, GPA has developed a type of target site resistance to synthetic pyrethroids (e.g. alpha-cypermethrin) and carbamates (e.g. pirimicarb), which is very problematic as it results in complete insecticide ineffectiveness and control failures when using these mode of action chemical sub-groups.

We have also seen Australian GPA develop a type of metabolic resistance to organophosphates (e.g. dimethoate).

The mechanism underlying organophosphate resistance is unusual in that it can be ‘switched on’ in response to particular stressors. This means organophosphates can be effective in some instances, although complete control failures have been known to occur (so there are no guarantees!).

And now recently, a type of metabolic resistance to neonicotinoids (e.g. imidacloprid) has been detected in Australian GPA.

While this metabolic resistance to neonicotinoids is considered ‘low-level’ and we don’t expect it to result in control failures at the moment, it serves as a timely reminder to exercise a resistance management strategy.

A very problematic form of target-site resistance to neonicotinoids can develop in GPA (it has happened overseas). It is crucial that this target-site resistance to neonicotinoids does not develop as it would give GPA cross-resistance to sulfoxaflor (Transform®).

Cover image: Photo by Julia Severi, Cesar Australia

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