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The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a highly destructive agricultural pest. The ability of S. frugiperda to survive and reproduce is widely recognized, but it is also important to consider the role of larval cannibalism as a significant biological trait. Understanding the cannibalistic habits of pests helps to explore the dynamics and evolution of their populations and facilitates the monitoring of insect outbreaks. Therefore, the stages, densities, and intensity of cannibalism in S. frugiperda larvae, as well as the consequences for their development, were investigated under laboratory conditions. Spodoptera frugiperda larvae showed obvious cannibalism after the third instar even in the presence of maize (Zea mays L., Poaceae) leaves; cannibalism was not observed in first instars. In the case of only one cannibal, the percentage of prey consumed by cannibalism decreased with higher prey density, and the predatory functional responses of fourth‐ to sixth‐instar predators to first‐ to third‐instar preys were fitted using the Holling II model. Compared with larvae feeding on maize only, larvae feeding on a diet of maize supplemented with third‐instar conspecifics had a longer developmental duration and a higher body weight, with no significant differences in larval survival, pupation, or eclosion rates. Larvae supplied with conspecifics only, in the absence of maize leaves, generally had a lower body weight than larvae supplied with maize only, although developmental duration was still longer, and longevity and fecundity rates were lower for these larvae. Overall, consuming a small quantity of conspecifics in addition to maize leaves prolonged the developmental duration of larvae and pupae to some extent, increased the body weight, and did not impact the longevity or reproduction of S. frugiperda. However, cannibalism only, without access to maize leaves, had a detrimental effect on adult longevity and reproduction. These findings could serve as a valuable reference for studying the life history of insects that consume agricultural crops and may have potential applications for biological control. [ABSTRACT FROM AUTHOR]

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is an important insect pest of maize (Zea mays L., Poaceae). The use of synthetic insecticides to control this pest remains the most popular option amongst growers. Natural insecticides offer a safer alternative to synthetic insecticides for controlling FAW. This study aimed to investigate the lethal and sublethal effects of a calcium carbonate formulation against this invasive insect pest. The tested formulation was a mixture of calcium carbonate (five concentrations), wetting agent and dispersant agent. Four experiments were conducted including a direct contact test, a no‐choice feeding test, a choice feeding test and an oviposition test. The application of the calcium carbonate formulation on maize leaves had a strong anti‐oviposition effect for adult female FAW, but a low‐to‐moderate antifeedant effect on FAW larvae. The growth and development of FAW larvae were only slightly affected by the calcium carbonate formulation in the feeding and the direct contact tests. The lethal effects of the calcium carbonate formulation against FAW larvae were low in direct contact and feeding tests. These results indicate that a calcium carbonate formulation has the potential to be used as the push component in a push–pull strategy for FAW control. Considering its low toxicity, both through direct contact and feeding, calcium carbonate can be an environmentally friendly alternative for the management of FAW. [ABSTRACT FROM AUTHOR]

Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), has a long association with maize (Zea mays mays L., Poaceae) and is among the crop's most significant pests worldwide. We contrasted the preference for and performance of FAW on three maize cultivars: the Mexican landrace Tuxpeño, the USA inbred B73 and B73‐lox10; B73‐lox10 is deficient in production of jasmonic acid (JA), green leaf volatiles (GLVs) and herbivore‐induced plant volatiles (HIPVs). Female oviposition and neonate colonization preferences were assessed in triple‐choice tests in greenhouse settings. Performance was assessed on the bases of larval, pupal and adult weights, larval and pupal development times, and adult longevity. We expected females to preferentially oviposit on plants on which their offspring performed best, and neonates to randomly colonize plants because they disperse aerially, presumably oriented solely by wind currents. Females preferred to oviposit on Tuxpeño plants, followed by B73‐lox10 and B73 plants, whereas their offspring performed best on B73‐lox10 and poorest on Tuxpeño. In contrast, neonates preferentially colonized plants on which they performed best, B73‐lox10, though initially and transiently they colonized plants on which they performed poorly, B73 and Tuxpeño. Altogether, our results showed that FAW females preferred to oviposit on maize plants on which their offspring's performance was poorest (Tuxpeño), and neonates preferentially colonized plants on which their own performance was best (B73‐lox10), though they initially colonized plants that were detrimental to their performance (Tuxpeño, B73). These results suggested that the ovipositional choices of FAW mothers are uncoupled from their offspring's performance, but newborn offspring rectified their mother's sub‐optimal host plant choice by colonizing plants that enhanced their own performance. Notably, these results also suggested that aerially dispersing (ballooning) FAW larvae do not colonize plants randomly, and that plant volatiles (GLVs, HIPVs) and JA may be relevant to host plant selection by ballooning larvae. [ABSTRACT FROM AUTHOR]

Trehalase (TRE) is a key enzyme for degrading trehalose, which plays a vital role in the growth and development of insects. Although validamycin, a compound belonging to a class of efficient antibiotics and fungicides, can control pests by suppressing TRE activities, it remains unknown whether it acts on both trehalose and chitin metabolism in Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), a major pest of maize (Zea mays L., Poaceae). This study investigated the changes in trehalose metabolism after validamycin treatment in S. frugiperda and its effects on the downstream chitin synthesis pathway. Compared with the control, S. frugiperda exhibited varying degrees of mortality after treatment with four concentrations of validamycin, showing a dose‐dependent increase in mortality rate. The mortality rates 24 and 48 h after treatment with 0.07 mg μL−1 validamycin were 35.6% and 42.2%, respectively, indicating the effective lethal concentration. Treatment with 0.07 mg μL−1 validamycin led to developmental delay, abnormal molting, and death in S. frugiperda, but it exerted no lasting effects on the survival rate, pupal weight, and phenotype during its subsequent developmental stages. At 24 h after validamycin treatment, TRE1 and TRE2 activities and glucose content decreased significantly, whereas the trehalose content increased significantly. Treatment with validamycin significantly upregulated TRE1 and TRE2 expression after 24 and 48 h and downregulated the mRNA expression of chitin synthase A and B genes. However, after 72 h, chitin content was not significantly affected. Hence, validamycin can destroy the dynamic transformation balance of trehalose and glucose by inhibiting the activities of the two TREs, and further affect the expression of downstream chitin synthase genes. These findings provide a theoretical basis for using TRE inhibitors to control S. frugiperda. [ABSTRACT FROM AUTHOR]