Study on the damage of Spodoptera frugiperda to ears of different maize cultivars

Objective  To investigate the damage of Spodoptera frugiperda to ears of 22 maize cultivars widely planted in Guangdong Province.

Method  The damage of corn ear was investigated by “Z” shaped five-point sampling method. The damage of the upper and lower corn ears of each plant, including the numbers of 1st to 3rd instar larvae, 4th to 6th instar larvae, live insects, live pupae and the damage position drilled by larvae were recorded.

Result  Twenty-two maize cultivars were all damaged seriously by S. frugiperda and the ratios of damaged plants were higher than 25% for all cultivars, while there were significant differences in damage degree among different cultivars. The sweet corns suffered the most serious damage compared to other cultivars, especially the ratio of damaged plants of ‘Yuetian 16’ was up to 99.67%. There was no significant difference in damage between the upper and lower corn ears for each cultivar except ‘Yuenong 19’ and ‘Guangcainuo 19’. Majority of corn ears had S. frugiperda larvae and the ratio of corn ear containing 1 and 2 larvae was 26% − 85%, the ratio of corn ear containing 3 larvae was 2% − 17%, while no corn ear was found to have more than 3 larvae. The number of 4th to 6th instar larvae was higher than that of 1st to 3rd instar larvae for each cultivar except ‘Guangnuo 9’ and ‘Guangnuo 2005’. Ranging from 38% to 71% S. frugiperda larvae entered into corn ear from corn silk and pupated, and the average number of pupae per 100 plants were 9−32.

Conclusion  S. frugiperda prefer to eat sweet corn and waxy corn and pupate in their ears, while the damage to feed corn is relatively light. The 1st−3rd and 4th−6th instar larvae of S. frugiperda have the same feeding behavior during the milky stage of corn and they prefer to enter into corn ear from corn silk and damage corn. The results can provide references for breeding resistant corn cultivars and precise control of S. frugiperda.