The fall armyworm, Spodoptera frugiperda, is a species native to the Americas and has spread to many countries in Africa and Asia in recent years. Proactive actions for potential invasion of S. ...frugiperda to China coordinated by government agencies and agricultural extension systems resulted in timely detection in January 2019 in Yunnan province neighboring onto Myanmar. The extensive monitoring in southern provinces of China since February 2019 resulted in dynamic tracking of S. frugiperda spreading to 13 provincial regions in China within 4 months by May 10, 2019, which is crucial for timely management actions in the fields. The first detections of S. frugiperda (corn strain) in China were confirmed using cytochrome oxidase subunit 1 (CO1) and triosephosphate isomerase (Tpi) genes molecular marker method. In addition to S. frugiperda, larvae of three other noctuid species with similar morphological appearance (S. litura, S. exigua and Mythimna separata) can occur simultaneously and cause similar damage in cornfields in southern China. Thus, we can use both morphological and molecular marker methods to compare larval stages of four noctuid species. Further, we discuss the risk of potential spread of invasive S. frugiperda to other regions and impact on corn production in China.
•Trichogramma species are being used for corn pests in China.•Technology for mass-rearing of Trichogramma has advanced.•Release techniques for Trichogramma in China are described.•Trichogramma ...release offers ecological and economic benefits in China.•Future prospects and challenges for Trichogramma technology.
Corn (Zea mays L., Poaceae) is ranked first as food crop in planting area and in total yield production in China. Asian corn borer, Ostrinia furnacalis, is the most destructive pest of corn in China, causing 6–9 million tons of yield loss per year on average. Trichogramma has been released for control of Asian corn borer at large scale since the 1970’s, partly triggered by the fact that Trichogramma dendrolimi can be successfully mass reared on eggs of the Chinese oak silkworm, Antheraea pernyi. Eggs of different hosts, such as Eri-silkworm, Samia cynthia ricini, A. pernyi, the Rice moth, Corcyra cephalonica, the Angoumois grain moth, Sitotroga cerealella and also artificial host eggs were tested and successfully used to mass-rear various Trichogramma species in China since then. The mass production technology and release technique of Trichogramma have been greatly improved in recent years making Trichogramma production and field application more practical and cost efficient. Nowadays, nearly 4 million hectares of corn are treated with T. dendrolimi, Trichogramma chilonis and Trichogramma ostriniae annually, mainly in North-east China. Large ecological and economic benefits have been achieved in areas where Trichogramma have been released continuously for many years. This includes an increase of natural populations of Trichogramma and other natural enemies in cornfields, the avoidance of any insecticide treatments in corn, a reduction in mycotoxin contamination and overall higher yields. The release of Trichogramma for controlling Asian corn borer and other lepidopteran pests became one of the key measures in corn IPM in China. Trichogramma applications combined with other non-chemical control measures for corn insect pests IPM began a new era in China as the new concept of “Public Plant Protection, Green Plant Protection” was put forward in 2006 as the guideline for plant protection in China. The future prospects and challenges of Trichogramma application are also discussed in this review.
Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), is a major polyphagous pest with the potential to seriously damage various crops. A better understanding of FAW's performance on different ...hosts may help to predict which plants will be attacked when the preferred host is absent, and facilitate the development of effective pest management practices. We compared the larval performance of FAW fed on maize with that of FAW fed on potato and tobacco, which are important crops in China, using an age‐stage two‐sex life table and adult female oviposition preference experiments. In cage experiments with potato, tobacco, or maize as the host, FAW reared on maize exhibited the strongest performance with shorter developmental time in the larval stage, longer longevity, and a higher reproductive rate in adults. Females oviposited on maize in preference to potato or tobacco. Compared with larvae fed on maize, those fed on potato and tobacco exhibited significantly lower survival, with only 31.61% and 8.13% developing to the adult stage, respectively. Several life table parameters, including the mean generation time (T), net reproductive rate (R0), finite rate of increase (λ), and intrinsic rate of natural increase (r) were negatively affected in FAW fed on potato and tobacco. Our results support the preference–performance hypothesis, that is, that herbivore females maximize fitness by choosing host plants associated with strong larval performance. Although larvae and adults performed poorly on potato and tobacco, their offspring will be capable of establishing populations on them, posing a potential threat to these crops in China.
Odorant binding proteins (OBPs) play a central role in transporting odorant molecules from the sensillum lymph to olfactory receptors to initiate behavioral responses. In this study, the OBP of ...Macrocentrus cingulum McinOBP1 was expressed in Escherichia coli and purified by Ni ion affinity chromatography. Real-time PCR experiments indicate that the McinOBP1 is expressed mainly in adult antennae, with expression levels differing by sex. Ligand-binding experiments using N-phenyl-naphthylamine (1-NPN) as a fluorescent probe demonstrated that the McinOBP1 can bind green-leaf volatiles, including aldehydes and terpenoids, but also can bind aliphatic alcohols with good affinity, in the order trans-2-nonenal>cis-3-hexen-1-ol>trans-caryophelle, suggesting a role of McinOBP1 in general odorant chemoreception. We chose those three odorants for further homology modeling and ligand docking based on their binding affinity. The Val58, Leu62 and Glu130 are the key amino acids in the binding pockets that bind with these three odorants. The three mutants, Val58, Leu62 and Glu130, where the valine, leucine and glutamic residues were replaced by alanine, proline and alanine, respectively; showed reduced affinity to these odorants. This information suggests, Val58, Leu62 and Glu130 are involved in the binding of these compounds, possibly through the specific recognition of ligands that forms hydrogen bonds with the ligands functional groups.
is a major herbivore insect in the fruit orchards of China that has become a devastating invasive pest in North America and Europe since its accidental introductions in the 1990s and 2000s, ...respectively. Like other hemipteran insects,
releases defensive chemicals against natural enemies, including (
)-2-decenal, which is an aldehyde associated with alarm pheromones. In this study, a series of electrophysiological and behavioral tests were conducted to characterize the alarm functions of (
)-2-decenal among
adults and nymphs. An antennal transcriptome was obtained from a Chinese
population, and 44 odorant-binding protein (
) genes were annotated. Among them, five putative alarm pheromone-binding proteins were screened and were extremely consistent with their homologs from US populations. These five OBPs were later expressed in a heterologous expression system, harvested, and then challenged with (
)-2-decenal in a binding assay. All five OBPs showed high binding activities to (
)-2-decenal, which demonstrated its behavioral significance as a defensive component in
, as well as being the first report of its olfactory reception. These findings will help develop behavioral-mediating tools as part of integrated pest management approaches to control this invasive pest.
In the Asian corn borer (ACB),
(Guenée), diapause is governed by a multigenetic constitution that responds to daylength and temperature with seasonality. The ACB displays uni- or multivoltinism, ...depending on its geographic specificity. Hence, warmer temperatures may result in alternation of voltinism in the ACB, which will help in understanding the ecological consequences of climate warming on insects. In the present study, we investigated the voltinism in two natural populations from Harbin (H) and Gongzhuling (G) as well as a laboratory (L) population (established from the H population in 2017) of the ACB, at ambient and elevated atmospheric CO
(
CO
390 μL/L and
CO
750 μL/L) and temperature (
T and
t =
t + 2 °C). From the diapause response, both the uni- and multivoltine ecotypes were coexisting in the H population. The neonate occurrence date of 50% individuals that induced diapause was ca. 10 days later in the G population than in the H population, but it was about 10 days earlier than in the L population. Comparing to the dates of onset and the peak of diapause induction, the G and L populations were less variable than the H population in response to a short and/or shortening daylength in the field. The univoltine individuals could not be eliminated completely after 19 generations of selection. Diapause incidence decreased with a climate-warming scenario, which was temporally specific and could be overridden by significantly low daily average temperatures. The
CO
did not directly impact the voltinism. On the basis of voltinism, the H population was sympatric for uni- and multivoltine ecotypes, with multivoltinism being dominant. The univoltinism trait was recessive. Climate warming could significantly override the effect of photoperiod, which was yearly dependent. Warmer temperatures and a decreased latitude (shortened daylength), and their interaction, would drive ACB evolution toward diapause homogeneity for multivoltinism.
Asian corn borer, Ostrinia furnacalis (Guenée), is a key corn pest in the Asian‐Western Pacific countries. It overwinters as full‐grown larvae in plant stalks or in a spun‐silk covering located in ...the plant debris in the temperate regions of China. Supercooling point (SCP) and survival rate after low sub‐zero temperature treatment were assessed for field‐collected populations in the laboratory using a cool bath with a 1°C/min cooling rate until −40°C. Mean SCPs were varied among geographical populations, with a significant decline from −22.7°C of Haikou, the multivoltine tropical population in the south, to −28.5°C of Gongzhuling, the univoltine temperate population in the northeast of China. In addition, there was more than 1°C difference in SCP between Gongzhuling univoltine and bivoltine populations that were from the same geographic origin. Mean SCPs of the Guangzhou population fluctuated over the year, with significantly lower SCPs in winter than in other seasons, which correlated with a significantly higher proportion of diapausing larvae in winter than in other seasons. Over 41% of overwintering larvae from the northeast population could withstand to be supercooled for a few minutes to the low sub‐zero temperature of −40°C, but only 6.7% of their southern counterparts did so. The findings from this study suggest that O. furnacalis mostly takes advantage of freeze avoidance as diapausing larvae for overwintering in the southern region, whereas it exhibits freeze tolerance in diapause in the northeastern region.
The potential effects of insect‐resistant, genetically engineered (GE) crops on non‐target organisms, especially on predators and parasitoids, must be evaluated before their commercial cultivation. ...The effects of GE maize that produces Cry1Ac toxin on the parasitoid Macrocentrus cingulum were assessed by direct bioassay and indirect bioassay. In the indirect bioassay, parasitism rate, cocoon weight and the number of M. cingulum progeny produced per host were significantly reduced when M. cingulum‐parasitized Cry1Ac‐susceptible Ostrinia furnacalis were fed a diet containing purified Cry1Ac; however, life‐table parameters of M. cingulum were not adversely affected when the same assay was performed with Cry1Ac‐resistant O. furnacalis. These results indicated that the detrimental effects detected with a Cry1Ac‐susceptible host were mediated by poor host quality. In a direct bioassay, no difference in life‐table parameters were detected when M. cingulum adults were directly fed a 20% honey solution with or without Cry1Ac; however, survival and longevity were significantly reduced when M. cingulum adults were fed a honey solution containing potassium arsenate, which was used as a positive control. The stability and bioactivity of Cry1Ac toxin in the food sources and Cry1Ac toxin uptake by the host insect and parasitoid were confirmed by enzyme‐linked immunosorbent assay and sensitive‐insect bioassays. Our results demonstrate that M. cingulum is not sensitive to Cry1Ac toxin at concentrations exceeding those encountered in Bacillus thuringiensis maize fields. This study also demonstrates the power of using resistant hosts when assessing the risk of genetically modified plants on non‐target organisms and will be useful for assessing other non‐target impacts.
Maize was introduced into opposite sides of Eurasia 500 years ago, in Western Europe and in Asia. This caused two host‐shifts in the phytophagous genus Ostrinia; O. nubilalis (the European corn ...borer; ECB) and O. furnacalis (the Asian corn borer; ACB) are now major pests of maize worldwide. They originated independently from Dicot‐feeding ancestors, similar to O. scapulalis (the Adzuki bean borer; ABB). Unlike other host‐plants, maize is yearly harvested, and harvesting practices impose severe mortality on larvae found above the cut‐off line. Positive geotaxis in the ECB has been proposed as a behavioural adaptation to harvesting practices, allowing larvae to move below the cut‐off line and thus escape harvest mortality. Here, we test whether the same behavioural adaptation evolved independently in Europe and in Asia. We sampled eight genetically differentiated ECB, ACB and ABB populations in France and China and monitored geotaxis through the entire larval development in artificial stacks mimicking maize stems. We find that all ECB and ACB populations show a similar tendency to move down during the latest larval stages, a behaviour not observed in any European or Asian ABB population. The behaviour is robustly expressed regardless of larval density, development mode or environmental conditions. Our results indicate that maize introduction triggered parallel behavioural adaptations in Europe and Asia, harvest selection presumably being the main driver.
Macrocentrus cingulum is an important polyembryonic endoparasitic wasp that attacks larvae of the Asian corn borer, Ostrinia furnacalis (Guenée) and the European corn borer, O. nubilalis (Hübner). ...Parasitoids use antennae as the main sensory organ to recognize herbivore-induced plant volatiles as host searching cues. The antennal olfaction proteins, odorant receptors (ORs) and ionotropic receptors (IRs) are involved in olfactory signal transduction pathway as a sensory neuron response. In the present study, we constructed a cDNA library from the male and female antennae for identifying the olfaction-related genes in M. cingulum. For that, we sequenced 3160 unique gene sequences and annotated them with gene ontology (GO), cluster of orthologous groups of proteins (COG), and KEGG ontology (KO). Through the homology search, we identified 9 odorant receptors (ORs), 3 ionotropic receptors (IRs) and 1 odorant binding protein (OBP) genes from the cDNA library sequences. Additionally, the expression patterns of these ORs and IRs in different tissues (antennae, heads, thoraxes, abdomens, and legs) were demonstrated by RT-PCR. The qualitative gene expression analyses showed that most of the OR genes were more highly expressed in female than male antennae; whereas IRs, unlike ORs, were more expressed in various male than females tissues. We are the first to report ORs and IRs in M. cingulum, which should help in deciphering the molecular basis of olfaction system in this wasp.
PDF
