Invasion of fall armyworm led to the succession ofmaize pests in Southwest China

The invasive fallarmyworm Spodoptera frugiperda (J. E. Smith) invaded Asia in2018, colonizing the tropical and southern subtropical regions as well asmigrating with the monsoons into Northeast Asia during spring and summer. This has resulted in widespread infestations,with significant impacts on maize production in various Asian countries. Previous studies have shown that the invasionof this pest can alter the species relationships of maize pests, but the actualimpact on maize pest management is still unclear. This study investigated the changes in maizepest occurrence and pesticide use in the annual breeding areas of S. frugiperda in Yunnan Province and the Guangxi Zhuang Autonomous Region of China during2017–2021, based on surveys and interviews with small farmers in maizeproduction. The results showed that S. frugiperda has emerged as the dominant species among maize pests after invasion andcolonization, replacing traditional pests such as Ostrinia furnacalis, Spodoptera litura, Agrotis ypsilon, and Rhopalosiphum maidis. The variety of pesticidesused for maize pest control has changed from chlorpyrifos, lambda-cyhalothrin,and acetamiprid to emamectin benzoate-based pesticides with high effectivenessagainst S. frugiperda. Furthermore, the frequency of maize pest chemical applications hasincreased from an average of 5.88 to 7.21 times per season, with the amounts ofpesticides used in summer and autumn maize being significantly higher than inwinter and spring maize, thereby increasing application costs by more than 35%. The results of this study clarified theimpact of S. frugiperda invasion on maize pest communitysuccession and chemical pesticide use in tropical and south subtropical China,thereby providing a baseline for modifying the regional control strategies formaize pests after the invasion of this relatively new pest.