Comparison of infestation rates of fall armyworm (Lepidoptera: Noctuidae) neonates for maize resistance screening

Authors: Woolfolk, Sandra; Matthews Jr, Gerald; Read, Quentin

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Fall armyworm (FAW) is a major global pest that feed above-ground corn plants mainly the whorl parts. One way to measure resistance of corn to FAW is visual rating of corn leaf-damage after infestation of the first stage of worms (also known as neonates) into the whorl. The objective of this study was to compare leaf-feeding damage ratings after infestation with different rates of FAW neonates. The main goal was to choose the smallest rate which could give the same damage effect on corn leaves as the larger rates. Four susceptible and six resistant corn germplasm lines were planted in replicated experiments with a split plot arrangement in the field in the summer of 2023 and 2024. The treatment was 10-, 20-, 30-, 40-, and 50-neonate infestation rates and plants were infested with neonates at these rates followed with leaf-feeding damage (LFD) scored 14 days later. In general 10-neonates infestation rate showed less damage compared to the higher rates indicating much less pressure from FAW to exhibit resistance in corn regardless of the genotypes. Overall results showed that 30- and 40-neonate infestation rates in both 2023 and 2024 were not different in the LFD scores. These two rates were able to differentiate the damage between susceptible and resistant lines; hence 30-neonate rate could be used for future infestation in the corn research program.

Technical Abstract: An economically important global maize pest, fall armyworm (FAW, Spodoptera frugiperda), causes damage mainly to the above-ground parts of maize plants, primarily the whorl tissues. One of our research unit missions is to identify and develop maize germplasm with resistance to FAW. One method to measure resistance in maize to FAW is visual rating of leaf-feeding damage after infestation with neonates into the whorl. The objective of this study was to compare leaf-feeding damage ratings after infestation with different rates of FAW neonates. The ultimate goal was to select the smallest infestation rate which could give the same damage effect on maize leaves as the larger infestation rates. Four susceptible and six resistant maize germplasm lines were planted in replicated experiments with a split plot arrangement in the field in the summer of 2023 and 2024. Plants were infested with FAW at 10-, 20-, 30-, 40-, and 50-neonate infestation rates (treatment). Leaf-feeding damage (LFD) was scored 14 days after infestation. In general 10-neonates infestation rate exhibited less damage in comparison to the higher infestation rates indicating much less pressure from FAW to exhibit resistance in maize regardless of the genotypes. Overall results showed that 30- and 40-neonate infestation rates in both 2023 and 2024 were not different in the LFD scores. These two rates were able to clearly distinguish the damage between susceptible and resistant lines; hence 30-neonate rate could be used for future infestation in the maize research program.