Toxicity of entomopathogenic fungi against Spodoptera frugiperda larvae under laboratory conditions

Maize Fall Armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae) is considered an economically important pest and becoming the main threat to food security. This polyphagous pest is widely distributed in various countries of the world especially tropical and subtropical regions. The toxicity of two entomopathogenic fungi such as Metarhizium anisopliae and Beauveria bassiana were evaluated against 2nd instar larvae of FAW under controlled conditions. The results showed that among tested entomopathogenic fungi, B. bassiana was found more toxic than M. anisopliae. B. bassiana caused 79% larval mortality while M. anisopliae 59%. M. anisopliae and B. bassiana were showed LT50 of 84.01 h and 80.99 h, respectively. M. anisopliae and B. bassiana were showed LC50 of 1.3×107 and 1.8×107 spores ml−1, respectively. The current study concluded that Entomopathogenic fungi can give effective control against early instar and further studies are needed to check the efficacy against older instars under field and laboratory conditions.

Hex Hox: De Novo Transcriptome Assembly and Embryonic Hox Gene Expression in the Burrowing Mayfly Hexagenia Limbata (Ephemeridae)

Background: Hox genes are key regulators of appendage development in the insect body plan. The body plan of Mayfly (Ephemeroptera) nymphs differs due to the presence of evolutionarily significant abdominal appendages called gills. Despite mayflies’ basal phylogenetic position and novel morphology amongst insects, little is known of their developmental genetics. Here we present an annotated transcriptome for the mayfly Hexagenia limbata, with annotated sequences for putative Hox peptides and embryonic expression profiles for the Hox genes Antp and Ubx/abd-A. Results: Transcriptomic sequencing of early instar H. limbata nymphs yielded a high-quality assembly of 83,795 contigs, of which 22,975 were annotated against Folsomia candida, Nilaparvata lugens, Zootermopsis nevadensis and UniRef90 protein databases. Peptide annotations included eight of the ten canonical Hox genes (lab, pb, Dfd, Scr, Antp, Ubx, abd-A and Abd-B), most of which contained all functional domains and motifs conserved in insects. Expression patterns of Antp and Ubx/abd-A in H. limbata were visualized from early to late embryogenesis, and are also highly conserved with patterns reported for other non-holometabolous insects.Conclusions: We present evidence that both H. limbata Hox peptide sequences and embryonic expression patterns for Antp and Ubx/abd-A are extensively conserved with other insects. These findings suggest mayfly Antp and Ubx/abd-A play similar appendage promoting and repressing roles in the thorax and abdomen, respectively. The identified expression of Ubx and abd-A in early instar nymphs further suggests that mayfly gill development is not subject to Ubx or abd-A repression. Previous studies have shown that insect Ubx and abd-A repress appendages by inhibiting their distal structures, which can permit the development of proximal appendage types. In line with past morphology-based work, we propose that mayfly gills are proximal appendage structures, possibly homologous to the proximal appendage structures of crustaceans.

Staying in touch: how highly specialised moth pollinators track host plant phenology in unpredictable climates

Background For specialised pollinators, the synchrony of plant and pollinator life history is critical to the persistence of pollinator populations. This is even more critical in nursery pollination, where pollinators are obligately dependant on female host plant flowers for oviposition sites. Epicephala moths (Gracillariidae) form highly specialised nursery pollination mutualisms with Phyllanthaceae plants. Several hundred Phyllanthaceae are estimated to be exclusively pollinated by highly specific Epicephala moths, making these mutualisms an outstanding example of plant–insect coevolution. However, there have been no studies of how Epicephala moths synchronise their activity with host plant flowering or persist through periods when flowers are absent. Such knowledge is critical to understanding the ecology and evolutionary stability of these mutualisms. We surveyed multiple populations of both Breynia oblongifolia (Phyllanthaceae) and it’s Epicephala pollinators for over two years to determine their phenology and modelled the environmental factors that underpin their interactions. Results The abundance of flowers and fruits was highly variable and strongly linked to local rainfall and photoperiod. Unlike male flowers and fruits, female flowers were present throughout the entire year, including winter. Fruit abundance was a significant predictor of adult Epicephala activity, suggesting that eggs or early instar larvae diapause within dormant female flowers and emerge as fruits mature. Searches of overwintering female flowers confirmed that many contained pollen and diapausing pollinators. We also observed diapause in Epicephala prior to pupation, finding that 12% (9/78) of larvae emerging from fruits in the autumn entered an extended diapause for 38–48 weeks. The remaining autumn emerging larvae pupated directly without diapause, suggesting a possible bet-hedging strategy. Conclusions Epicephala appear to use diapause at multiple stages in their lifecycle to survive variable host plant phenology. Furthermore, moth abundance was predicted by the same environmental variables as male flowers, suggesting that moths track flowering through temperature. These adaptations may thereby mitigate against unpredictability in the timing of fruiting and flowering because of variable rainfall. It remains to be seen how widespread egg diapause and pre-pupal diapause may be within Epicephala moths, and, furthermore, to what degree these traits may have facilitated the evolution of these highly diverse mutualisms.

Effects of sex ratio on different biological parameters of Engytatus varians (Distant) (Hemiptera: Miridae) adults and their offspring: prey preference for Bactericera cockerelli (Sulcer) (Hemiptera: Triozidae)

In the present study, the influence of three sex ratios (1:1, 1:2, and 1:3; female:male) of the mirid Engytatus varians (Distant) (Hemiptera) on different biological parameters and on its offspring was evaluated. The prey preference of different developmental stages of this predator for different nymphal instars (N) of Bactericera cockerelli (Sulcer) (Hemiptera: Triozidae) was also evaluated. The fertility was significantly higher (24 nymphs/female) in the 1:3 sex ratio than in the 1:1 and 1:2 sex ratios (14 and 16 nymphs/female, respectively). The females in the 1:1 and 1:2 sex ratios lived 1.14 and 1.43 days more (27 and 28 days, respectively) than those in the 1:3 sex ratio (26 days). The nymphs derived from the females of the three sex ratios (first filial generation, F1) had five instars and a duration of 17 or 18 days. The ratio of the F1 generation females was not affected by the sex ratio of their parents. In choice tests, independent of whether the preys were placed on a single or multiple tomato (Solanum lycopersicum L.) leaflets, the consumption of females and males and N3, N4, and N5 nymphs of E. varians on B. cockerelli, generally showed the order of N2>N3>N4>N5. In conclusion, the findings revealed in this study can help to improve the rearing methodology for increasing populations of E. varians. In addition, they can serve as a guideline for releasing this predator in times when there is an abundance of early instar nymphs of B. cockerelli.

A rapid multiplex PCR assay for species identification of Asian rice planthoppers (Hemiptera: Delphacidae) and its application to early-instar nymphs in paddy fields

Rice (Oryza sativa L.) is the main cereal crop in many Asian countries. The Asian rice planthoppers, Nilaparvata lugens (Stål) (brown planthopper), Sogatella furcifera (Horváth) (white-backed planthopper), and Laodelphax striatellus (Fallén) (small brown planthopper) (Hemiptera: Delphacidae), are the most economically important pests of rice. These three rice planthopper species often co-occur in the same paddy field. Traditionally, species identification of individuals of the three rice planthopper species has relied on morphological characters, but accurate discrimination of early-instar nymphs is very difficult, even for expert researchers. In this study, we developed a rapid one-step multiplex PCR assay using conserved and species-specific 5.8S-ITS2 rDNA gene primers for simultaneous identification of individuals of the three rice planthopper species. The multiplex PCR results showed that the three rice planthopper species could be identified accurately based on the length of the resultant amplicon, regardless of the individual developmental stage. Furthermore, we applied this assay for the first accurate quantification of early-instar nymphs of each rice planthopper species in paddy fields. Notably, we found that the species composition of early-instar nymphs cannot be extrapolated from that of adults. Thus, the multiplex PCR assay developed here facilitates detection of each rice planthopper species at the beginning of outbreaks in paddy fields.

Effects of Dehumidification on the Survivorship of Four Psocid Species

Psocids are damaging stored-product pests. In this study, eggs and early-instar nymphs, adults, and all life stages of Liposcelis entomophila, L. decolor, L. bostrychophila, and L. paeta were subjected to 43, 50, or 75% (Control) relative humidity (RH) for 2, 4, 6, 8, 10, 12, 14, or 16 d at 30.0°C. All adults of these species died within 8 d at both 43 and 50% RH, except for L. bostrychophila, which required 12 d at 50% RH for 100% mortality to occur. For all life stages and eggs and early-instar nymphs, maximum survival times (times to 100% mortality) at 43 or 50% RH for L. entomophila, L. decolor, L. bostrychophila, and L. paeta, were 8 and 10 d, 8 and 12 d, 12 and 14 d, and 12 and 16 d, respectively. During this study, numbers of nymphs and adults of all species 14 d after the RH treatments increased within the 75% RH Control arenas. Different species and life stages responded differently to 43 and 50% RH, as time to kill all stages of the four psocid species was 8–12 and 10–16 d, respectively. Results indicate that using a specific RH environment may be effective in psocid management.

Staying in touch: how highly specialised moth pollinators track host plant phenology in unpredictable climates

For pollinating insects that visit just a single flowering species, the co-occurrence of flowers and insects in time is likely to have critical implications for both plant and pollinator. Insects often utilise diapause to persist through periods in which resources are unavailable, timing their re-emergence by responding to the same environmental cues as their host plants. The obligate pollination mutualisms (OPMs) between Epicephala moths (Gracillariidae) and their leaf flower host plants are some of the most specialised interactions between plants and insects. However, to date there have been very few studies of Epicephala moth lifecycles and none of how they synchronise their activity with the flowering of their host plants. Breynia oblongifolia (Phyllanthaceae) is known to be exclusively pollinated by two highly specific species of Epicephala moth (Gracillariidae). We surveyed populations of both the host plant and it’s pollinators over multiple years to determine their annual phenology and then modelled the climatic factors that drive their activity. Using our newly gained knowledge of moth and host plant phenology, we then looked for evidence of diapause at both the egg and pre-pupal stages. Our phenology surveys showed that although female flowers were present throughout the entire year, the abundance of flowers and fruits was highly variable between sites and strongly associated with local rainfall and photoperiod. Fruit abundance, but not flower abundance, was a significant predictor of adult Epicephala activity, suggesting that eggs or early instar larvae diapause within dormant flowers and emerge as fruits mature. Searches of overwintering flowers confirmed this, with many containing evidence of pollen and diapausing pollinators. We also observed the behaviour of adult Epicephala prior to pupation and found that ~10% of the Autumn emerging Epicephala enter diapause, eclosing to adulthood after 38-56 weeks. The remaining 90% of autumn emerging adults pupate directly with no diapause, suggesting a bet hedging strategy for adult emergence. As such, Epicephala moths appear to utilise diapause at multiple stages in their lifecycle, and possibly bet hedging, in order to deal with variable flowering phenology and climatic unpredictability.

16S rRNA Amplicon Sequencing of Bagworm Metisa plana Walker (Lepidoptera: Psychidae)

The bagworm Metisa plana is one of the major pests in the oil palm plantation in Malaysia, with infestation that results in huge economical loss. Currently, the exact cause of the infestation is still undetermined. Studying the bacterial community of M. plana could provide insight on the problem as the bacteria associated with insects often provide numerous benefits to the insect itself. Using 16S rRNA amplicon sequencing, the study was conducted to compare the composition of the bacterial communities of two larval stages (early instar stage and late instar stage) from outbreak area, as well as comparing the late instar stage larvae from non-outbreak and outbreak areas. Generally, the bacterial community was dominated by Proteobacteria and Actinobacteria phyla while the Enterobacteriaceae was found to be the dominant family. When comparing between the early and late instar stage, Proteobacteria phylum was found to be more abundant in the late instar stage (82.36%) than in the early instar stage (82.28%). At the family level, the Enterobacteriaceae was slightly more abundant in late instar stage (75.46%) than in early instar stage (75.29%). The instar stage was observed to have no significant impact on the bacterial variability and showed similar bacterial community structure. When comparing between the non-outbreak area and outbreak, Proteobacteria was significantly more abundant in the outbreak area (82.02%) than in the non-outbreak area (20.57%). However, Actinobacteria was significantly more abundant in the non-outbreak area (76.29%) than in the outbreak area (14.16%). At the family level, Enterobacteriaceae was more abundant in outbreak area (75.41%) than in non-outbreak area (11.67%). Microbacteriaceae was observed to be more abundant in the non-outbreak area (70.87%) than in the outbreak area (12.47%). Although the result showed no significant difference in bacterial variability between different areas, it the bacterial community structure was significantly different.