Evaluation of the resistance of three maize varieties to Spodoptera frugiperda (J.E. Smith) and Ostrinia nubilalis Hübner in the Tonkpi region (Man, Côte d'Ivoire).

Background: The corn borer Ostrinia nubilalis and the fall armyworm Spodoptera frugiperda larvae feed on the aerial parts of maize. It is responsible for significant yield losses and are therefore a cause of food insecurity. This study carried out to evaluate the resistance of three maize varieties (EV8766 SR-MRP, PR9131-SR, CEW-SR), in Tonkpi region's, to S. frugiperda and O. nubilalis damages. Each maize variety seeds were sown on a one hectare plot subdivided into 6 elementary plots with 75 cm between rows and 40 cm between bunches. Sampling of S. frugiperda and O. nubilalis larvae on maize plants was carried out according to the FAO method, from the third to the fifth week after planting. Maize plants damaged, the intensity of infestation and the number of larvae on maize plants were recorded. Maize plants damaged by the insect pests were marked to avoid recounting. At maturity, 100 maize cobs were harvested per elementary plot, then the larvae number and the attacked cobs by S. frugiperda and O. nubilalis larvae were recorded. Results: The lowest damage rate by S. frugiperda were recorded in maize variety EV8766-SR-MRP (23.33%); while, the highest damage rate were in the varieties PR9131-SR (43.33%) and CEW-SR (55%). There are no significant difference values of the density of S. frugiperda larvae per maize plant attacked between the three varieties. The index of intensification of maize plant damaged by S. frugiperda larvae was lower for the variety EV8766-SR-MRP (7.50%) and was moderate for the varieties PR9131-SR (15.42%) and CEW-SR (21.67%). The damage rates of O. nubilalis larvae on maize cobs varied between 9.6 and 22.0%. These damage rates were higher for the varieties PR9131-SR (21.83%) and CEW-SR (17.50%) and were lower for EV8766-SR-MRP (9.66%). There was not significantly different from the density of O. nubilalis larvae per maize cob attacked between the three varieties. It was between 1 to 1.2 larvae. Crop losses were lower for EV8766 SR-MRP (10.228%) than those of PR9131-SR and CEW-SR (19.338%). Conclusions: The maize variety EV8766-SR-MRP is found to be the best variety in the control of, O. nubilalis and S. frugiperda. [ABSTRACT FROM AUTHOR]