Insecticide susceptibility level and control failure likelihood estimation of Sub-Saharan African populations of tomato leafminer: Evidence from Burkina Faso

The South American tomato pinworm, Tuta absoluta Meyrick (Lepidoptera:
Gelechiidae) is a leafminer species currently considered as one of the major
pests of fresh tomatoes around the world. The species settled in north Africa in 2007,
before being observed in the entire continent. Widespread insecticide use has led to the
emergence of resistant populations in South America and Europe, but no large-scale
insecticide resistance assessment has been performed in Sub-Saharan Africa so far.
In this study, we collected T. absoluta larvae from locations widely distributed in
Burkina Faso, where the pest was first detected in 2016. Acute toxicity of the all
available molecules in Burkina Faso was evaluated in the laboratory on F1 individuals,
including acetamiprid, abamectin, spinosad, cypermethrin, chlorpyrifos, λ-cyhalothrin,
deltamethrin, and Bacillus thuringiensis. No LC50 differences among T. absoluta
populations were highlighted, except for Bacillus thuringiensis. Insects were still highly
susceptible to abamectin [LC50<0.4 mg/L; Control failure likelihood (CFL)=−25%],
spinosad (LC50<0.6 mg/L; CFL = 25%) and chlorpyrifos-ethyl (LC50 between 254
and 458 mg/L; CFL = −15%), but were less susceptible to acetamiprid (CFL ranging
from 72% to 91%), cypermethrin (CFL = 80%), λ-cyhalothrin (CFL =79%), and
deltamethrin (CFL ranging from 51% to 66%), with LC50 values for these insecticides
ranging between 100 and 525 mg/L. Pending a proper communication strategy, we hope
this work could help producers avoiding the most inefficient active substances