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, is a newly invasive, widespread agricultural pest in China.  Understanding the suitability of the main field crops in Chinese agricultural system as host for this polyphagous herbivore is especially important for making control strategy.  Here, after FAWs were fed three important oil-bearing crops (oilseed rape, soybean and sunflower) planted in China and resultant population parameters were compared using the age-stage, two-sex life table method, survival of larvae on soybean was significantly lower than that on oilseed rape and sunflower.  Developmental duration of larvae on soybean was also the longest (23.3 days).  The highest pupation rate was recorded on sunflower.  The highest pupal mass (0.19 g) was attained on oilseed rape, significantly higher than on the other host plants; the lowest mass was on soybean (0.15 g).  On soybean, oilseed rape and sunflower, respectively, the average generation period was 42.21, 39.10 and 40.44 d; the intrinsic rate of increase (r) was 0.0844, 0.1041 and 0.1134; the finite rate of increase (λ) was 1.0881, 1.1098 and 1.1202.  While the most suitable host plant overall was sunflower, S. frugiperda completed development and increased its population on all three host plants.  Thus, soybean, oilseed rape and sunflower were all suitable for FAW, and population monitoring and management of FAW in these crops should be increased.

 

In December 11, 2018, the fall armyworm (FAW), Spodoptera frugiperda invaded China and has since impacted local maize, sorghum and other crops.  Here, we draw on laboratory experiments to show how different host crops (i.e., maize, sorghum, wheat and rice) and artificial diet affect larval growth and adult reproduction of one local FAW strain.  Larval diet affected development duration, pupation rate, survival and emergence rate of pupae, and S. frugiperda adult fecundity.  FAW attained the slowest larval development (19.4 days) on sorghum and the fastest (14.1 days) on artificial diet, with larvae attaining 99.6% survival on the latter food item.  On rice, FAW larvae attained survival rate of 0.4% and were unable to pupate successfully.  Pupation rate and pupal survival varied substantially between artificial diet and live plantlets at different phenological stages.  Pupal weight was the highest (0.26 g) on artificial diet and the lowest (0.14 g) on sorghum, while FAW females reached the highest fecundity (699.7 eggs/female) on 2-leaf stage maize.  Egg hatching rate equaled 93.6% on 4- or 5-leaf stage maize and 36.6% on artificial diet.  FAW intrinsic rate of natural increase and the finite rate of increase varied between larval diets, reflecting how young maize leaves are the most suitable diet.  Our findings can help to refine laboratory rearing protocols, devise population forecasting models or guide the deployment of ‘area-wide’ integrated pest management (IPM) modules in FAW-invaded areas of China and other Asian countries. 

 

The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), has invaded many countries in Africa and Asia since 2016, posing a major threat to world food security.  Long-distance migration and strong reproductive ability form the biological basis of its rapid population expansion, but the relationship between the flight and reproduction of FAW has not been studied in depth.  Here, an empirical assessment of this relationship in an invasive FAW population in China found that 1–3-day-old adults which had undergone 10-h tethered flights had a significantly shorter pre-oviposition period and greater oviposition synchronization, but did not show any differences in fecundity, oviposition period, mating percentage or other reproductive variables.  Further studies on moths after 1.25–15-h tethered flights indicated that the reproductive process of adults could be fully triggered by flight activity longer than 2.5 h.  Dissection of the reproductive organs also showed that tethered flight promoted ovarian and testicular development of FAW.  These results show that appropriate moth flight activity significantly speeds up the reproductive process of FAW, which increases our knowledge on its migratory biology in relation to regional outbreaks.

 

Floral resources, such as carbohydrate-rich nectar or pollen, can bolster fitness and raise reproductive output of adult lepidopterans.  Here, we used laboratory experiments to assess how those plant-derived foods impact adult fecundity, reproductive physiology and flight performance of an invasive strain of the fall armyworm, Spodoptera frugiperda (FAW; Lepidoptera: Noctuidae) in China.  More specifically, supplementary feeding on bee pollen and honey enhanced FAW flight duration, testis size, ovarian development, longevity and adult fecundity.  FAW adults attained the longest pre-oviposition (10.8 days) and oviposition period (6.8 days) and longevity (19.2 days) on 5% acacia honey.  Upon access to 2.5% acacia honey and 2.5‰ pine pollen, S. frugiperda attained the highest mating rate (79.7%), fecundity (644.9 eggs/female) and egg hatching rate (82.3%).  Feeding on honey further delayed decay of male testes, while ovarian development was enhanced when female moths were allowed access to 2.5% honey and 2.5‰ pine pollen.  Upon feeding on 5% honey solution, S. frugiperda engaged in flight over the longest duration (9.5 h), distance (29.9 km) and speed (3.1 km h^–1).  Honey had a comparatively greater effect on the above parameters than pollen.  Our findings help decipher FAW invasion patterns and population dynamics, facilitate the development of nutritional attractants, and contribute to integrated pest management of this newly-invasive pest in eastern Asia.

In late 2018, the fall armyworm (FAW) Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) made its arrival in China and its populations have since proliferated across most of eastern Asia.  While S. frugiperda exhibits a considerable dispersal capacity and engages in long-distance migration, there’s only scant information on the species’ flight capability.  Here, we empirically assessed S. frugiperda flight activity under varying climatic conditions using a flight mill.  More specifically, under laboratory conditions, FAW exhibited superior flight performance at 20–25°C and 60–90% relative humidity (RH).  When quantifying flight performance over five consecutive nights (i.e., 10 h/night), all flight parameters initially increased and then gradually dropped and FAW adults attained a total flight distance, duration and velocity equal to 63.73 km (48.42–94.12 km) (median, quartile range), 24.12 h (20.87–27.73 h) and 2.73 km h^–1 (2.13–3.33 km h^–1), respectively.  Our work constitutes a first comprehensive assessment of S. frugiperda flight performance and provides baseline information for future efforts to forecast spatiotemporal changes in its geographical distribution, movement patterns and invasion trajectories.  Such can ultimately permit a timely and targeted deployment of area-wide pest management measures against this newly-invasive pest in China and across eastern Asia. 

The fall armyworm (FAW, Lepidoptera: Noctuidae), Spodoptera frugiperda (J. E. Smith), invaded China in mid-December 2018; since then, it has become a great threat to Chinese agricultural production.  Qinling Mountains–Huaihe River region (QM–HRR) is the transitional zone between northern and southern China, an important region for both corn and wheat production.  Based on the actual occurrence of QM–HRR invaded by FAW in 2019, daily mean surface air temperature and nocturnal wind conditions at 925 hPa were examined, and migratory routes of FAW moths originated in QM–HRR were modeled by a forward-trajectory-analysis approach.  The results indicated that migratory activities of FAW adults emerged in QM–HRR were initiated from late June.  The moths from western QM–HRR, where has complex topographic terrain, mainly flied to Ningxia and Inner Mongolia before mid September.  However, FAW moths from the eastern QM–HRR primarily engaged in high-altitude northward transport assisted by the prevailing southerly winds before mid August, and the North China Plain was identified as the main destination of FAW.  Meanwhile, the migration trajectories of FAW moths had a possibility to reach the Northeast China Plain.  From mid August, FAW moths in eastern QM–HRR largely migrated southward and returned to the Yangtze River Valley.  This study provides detailed information on the occurrence and migration routes of FAW moths from QM–HRR and will be helpful for early warning and development of integrated pest management strategies for the control of this exotic insect pest.