Methomyl resistance in Dalbulus maidis (Hemiptera: Cicadellidae): selection, inheritance and multiple-resistance

Acetylcholinesterase (AChE) inhibitor insecticides have been important tools for the management of Dalbulus maidis in Brazil; however, the selection pressure exerted by their extensive use has led to reduced susceptibility in field populations, particularly to the carbamate methomyl. To implement resistance management strategies for D. maidis resistance to methomyl, we selected a methomyl-resistant strain (Methomyl-R) from a field population of D. maidis collected from Goiás State to characterize the inheritance patterns and potential cross- or multiple-resistance to other insecticides.

The resistance ratio (RR), based on LC₅₀ of the field population divided by the LC₅₀ of the susceptible reference strain (SUS), increased from 9.73- to 163.42-fold over 26 generations of selection pressure. Conversely, the unselected strain (RV-Unsel) derived from the same field population decreased the RR from 9.73- to 4.09-fold after 28 generations. The reciprocal crosses between Methomyl-R and SUS indicated that resistance of D. maidis to methomyl is autosomal and incompletely dominant. Backcrosses between heterozygous strains and SUS suggested a polygenic architecture. Low cross-resistance was observed to the AChE inhibitors carbosulfan (5.63-fold) and acephate (8.93-fold), as well as to buprofezin (≈ 10-fold). High RRs were observed for neonicotinoids and pyrethroids (> 50-fold). No cross-resistance was detected for chlorfenapyr, cyantraniliprole or isocycloseram (< 5-fold).

The incompletely dominant inheritance of methomyl resistance may contribute to a high risk of resistance-associated control failure in D. maidis. Insecticides from different chemical groups including chlorfenapyr, cyantraniliprole and isocycloseram were identified as viable candidates for resistance management programs of D. maidis to methomyl. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.