Effect of maize seed treatment on oviposition preference, larval performance and foliar damage of the fall armyworm

The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith; Lepidoptera: Noctuidae), is an invasive pest that has recently become a major worldwide threat for maize production. Greatest crop yield reductions occur following damage by FAW larvae at early vegetative plant stages, between the first and second week after plant emergence. In this study, field and semi-field experiments were carried out to assess the effect of cyantraniliprole-based seed treatment on the protection of early stages of maize plants against FAW and the associated mechanisms. In the field, maize seed treatment using cyantraniliprole (Fortenza (R)) significantly reduced the percentage of infested seedlings (77%) and the percentage of seedlings with severe damage (86%) up to 3 weeks after emergence. In a choice situation, semi-field experiments showed that gravid moths preferred to lay eggs on plants from untreated seeds (68%) rather than on plants from treated seeds. To the best of our knowledge, this is the first evidence that insecticide residues present in plant tissues deter oviposition of Noctuid moths. Seed treatment with cyantraniliprole also reduced plant infestation (65%) 10 days after artificial inoculation of neonate larvae at 3 weeks after plant emergence, reducing the severity of leaf damage (by 67%). Insecticide seed treatment is a relevant tool for the integrated pest management of the FAW in high-value crops such as sweet corn, especially for reducing foliar applications of insecticides during the most susceptible stages of the crop, as far as the risk of impacts on non-target organisms is low and no alternative biocontrol option is available.