Spodoptera frugiperda, the pest fall armyworm (FAW), is widespread in more than 100 countries.  To date, planting insect-resistant transgenic crops is one of the main control methods in its native countries.  In this study we evaluated Bt-transgenic maize (Bt maize) and non-transgenic (conventional) maize and six other host plants in greenhouse pot experiments and field trials for oviposition preference by the Chinese populations of FAW.  In laboratory trials, female moths preferred to oviposit on maize with no significant preference between conventional and Bt maize.  However, after conventional and transgenic maize were exposed to FAW larvae and damaged, oviposition was significantly higher on transgenic maize than on the conventional one.  Field trials showed that for plants less damaged at an early stage (seedling stage), oviposition of FAW on transgenic and conventional maize was significantly higher than that on wheat, sorghum, foxtail millet, peanut and soybean while showing no significant difference between transgenic or conventional maize.  FAW adults mainly laid eggs on Bt maize, while the larval density and leaf damage rating or percentage of damaged plants were significantly lower than on conventional maize.  Larval density and its damage on conventional maize were significantly higher than that on Bt maize and the other five hosts.  Thus, maize is a highly preferred and suitable host for S. frugiperda feeding and ovipositing, and Bt maize can be used as trap crop to protect other crops.

The fall armyworm (FAW) Spodoptera frugiperda, which originated in the Americas, is advancing across China and threatening the nation’s maize crops.  Currently, one widely used tool for its control is genetically modified (GM) Bacillus thuringiensis (Bt) maize.  Sufficient content of Bt protein in appropriate plant parts is crucial for enhancing resistance against insect pests.  In this study, we conducted a systematic investigation of Cry1Ab levels in Chinese domestic GM maize DBN9936, which has recently obtained a biosafety certificate, and evaluated its efficacy against FAW.  Quantification of expression levels of Cry1Ab, via ELISA, indicated a spatio-temporal dynamic, with significant variation of mean Cry1Ab, ranging from 0.76 to 8.48 μg g^–1 FW with the Cry1Ab protein level ranked as: V6–V8 leaf>R1 leaf>R4 leaf>R1 silk>VT tassel>R4 kernel.  Among the nine locations, the Cry1Ab levels in DBN9936 of the Xinxiang, Langfang, and Harbin fields were significantly lower than those from Wuhan and Shenyang, and were slightly, but not significantly lower than those from the other four fields.  Furthermore, the artificial diet–Cry1Ab mixture and plant tissue feeding bioassays revealed that DBN9936 has high efficacy against FAW.  The insecticidal efficacy of different tissues against FAW larvae reached 34–100% with a descending order of lethality as follows: VT leaf>R4 leaf>R1 husk>R1 silk>VT tassel>R4 kernel.  Taken together, our results showed that Bt-Cry1Ab maize DBN9936 has potential as a promising strategy to manage FAW.

 

Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), has become an important pest in Chinese agricultural systems since its invasion on 11 December 2018.  After its establishment, FAW months in the year-round breeding region have become the main source population migrating to other areas in China.  Field investigations were conducted in tropical and subtropical regions to improve understanding of its year-round breeding area in China.  The results showed that FAW larval density was significantly correlated with the seasonal temperature of the location surveyed.  The FAW larvae maintained a high density in the tropical area and were frequently found in sites of the south subtropical region, but were absent from the north subtropical region and the northern part of the central subtropical region.  These results indicated that FAW can reproduce annually in the tropical and south subtropical regions of China, including Hainan, Taiwan and the southern area of Fujian, Guangdong, Guangxi, Guizhou, and Yunnan.  Hence, great effort should be made to monitor and control FAW in the year-round breeding region to suppress the population density of this area and to reduce migration of moths into northern parts of China.  This study clarifies the occurrence area of the pest in winter in China and provides much valuable information for its population forecasting and management.

Fall armyworm, Spodoptera frugiperda (J. E. Smith, 1797), a crop pest native to tropical and subtropical regions of America, has invaded and spread into most regions in China, posing a severe threat to China’s agriculture.  The cold hardiness directly determines its geographic distribution through adapting to winter temperatures of different regions.  Here, we measured supercooling points and lethal time (LT) at low temperatures of S. frugiperda.  The supercooling points for developmental stages in increasing order were: adults (–15.05°C)<pupae (–13.25°C)<prepupae (–10.50°C)<larvae (–9.03°C).  Among eggs and 1st to 4th instar larvae, the 99% lethal time (LT₉₉) was the highest for 4th instar larvae, with 99% of larvae dying after 18.59 d at 2°C, 58.72 d at 7°C, and 66.28 d at 13°C.  LT₉₉ was the lowest for eggs with LT₉₉ of 5.33 d at 2°C, 9.28 d at 7°C, and 12.97 d at 13°C.  This study provides an understanding of overwintering regions of S. frugiperda in China, which will be helpful for population forecasting and management.

The fall armyworm (FAW), Spodoptera frugiperda is one of the most damaging crop pests, and it has become major threat to the food security of many countries.  In order to monitor possible invasion of this pest into China, a searchlight trap was established in March 2018 in western Yunnan Province, China, where it has served as the “first station” for many pests that have migrated from Myanmar to China.  A number of suspected FAW moths were captured and identified by DNA sequencing.  The results showed that the FAW moth was first captured on December 11 and formed its first immigration peak in mid-December 2018.  DNA detection revealed that the early invading FAW population was the “corn-strain”.  The field survey indicated that the pest mainly colonized corn in Pu’er, Dehong and Baoshan areas.  Migration trajectory simulation implied that the moths might have mainly come from the eastern area in the mid-latitude region of Myanmar (20–25°N, 94–100°E).  This case study confirmed the first immigration of FAW into China, and will be helpful for guiding monitoring and management work to control this pest.