Mikania micrantha is a fast-growing global invasive weed species that causes severe damage to natural ecosystems and very large economic losses of forest and crop production.  It has advantages in photosynthesis, including a similar net photosynthetic rate as C₄ plants and a higher carbon fixation capacity.  We used a combination of genomics and transcriptomics approaches to study the evolutionary mechanisms and circadian expression patterns of M. micrantha.  In M. micrantha, 16 positive selection genes focused on photoreaction and utilization of photoassimilates.  In different tissues, 98.1% of the genes associated with photoresponse had high expression in stems, and more than half of the genes of the C₄ cycle had higher expression in stems than in leaves.  In stomatal opening and closing, 2 genes of carbonic anhydrase (CAs) had higher expression at 18:00 than at 8:00, and the slow anion channel 1 (SLAC1) and high-leaf-temperature 1 kinase (HT1) genes were expressed at low levels at 18:00.  In addition, genes associated with photosynthesis had higher expression levels at 7:00 and 17:00.  We hypothesized that M. micrantha may undergo photosynthesis in the stem and flower organs and that some stomata of the leaves were opening at night by CO₂ signals.  In addition, its evolution may attenuate photoinhibition at high light intensities, and enhance more efficient of photosynthesis during low light intensity.  And the tissue-specific photosynthetic types and different diurnal pattern of photosynthetic-related genes may contribute to its rapid colonization of new habitats of M. micrantha.

Global food security is threatened by the impacts of the spread of crop pests and changes in the complex interactions between crops and pests under climate change.  Schrankia costaestrigalis is a newly-reported potato pest in southern China.  Early-warning monitoring of this insect pest could protect domestic agriculture as it has already caused regional yield reduction and/or quality decline in potato production.  Our research aimed to confirm the potential geographical distributions (PGDs) of S. costaestrigalis in China under different climate scenarios using an optimal MaxEnt model, and to provide baseline data for preventing agricultural damage by S. costaestrigalis.  Our findings indicated that the accuracy of the optimal MaxEnt model was better than the default-setting model, and the minimum temperature of the coldest month, precipitation of the driest month, precipitation of the coldest quarter, and the human influence index were the variables significantly affecting the PGDs of S. costaestrigalis.  The highly- and moderately-suitable habitats of S. costaestrigalis were mainly located in eastern and southern China.  The PGDs of S. costaestrigalis in China will decrease under climate change.  The conversion of the highly- to moderately-suitable habitat will also be significant under climate change.  The centroid of the suitable habitat area of S. costaestrigalis under the current climate showed a general tendency to move northeast and to the middle-high latitudes in the 2030s.  The agricultural practice of plastic film mulching in potato fields will provide a favorable microclimate for S. costaestrigalis in the suitable areas.  More attention should be paid to the early warning and monitoring of S. costaestrigalis in order to prevent its further spread in the main areas in China’s winter potato planting regions.

In insects, ecdysteroids are synthesized by genes of the Halloween family and play important roles in several key developmental events, including molting and metamorphosis.  However, the roles of these genes in Agasicles hygrophila are still largely unknown.  In this study, the expression patterns of the two Halloween genes AhCYP307A2 and AhCYP314A1 were determined by quantitative PCR (qPCR) at different developmental stages.  Moreover, the functions of these two genes were explored using RNA interference (RNAi), and ovarian development was observed by dissecting the ovaries of A. hygrophila females.  The qPCR results showed that AhCYP307A2 and AhCYP314A1 were highly expressed in last instar larvae and in adult females.  In addition, AhCYP307A2 was also highly expressed in eggs and pupae but was markedly lower than in third-instar larvae and females.  The RNAi results showed that the injection of dsAhCYP307A2 or dsAhCYP314A1 markedly inhibited their expression and the transcription levels of three related AhVgs.  Knockdown of AhCYP307A2 or AhCYP314A1 significantly inhibited larval molting, impaired last instar larva–pupa–adult transition, delayed ovarian development, and stopped egg production (i.e., no eggs were laid).  These results indicate that AhCYP307A2 and AhCYP314A1 play important regulatory roles in last instar larva–pupa–adult transition and reproduction in A. hygrophila.

Leaf-mining flies (Diptera: Agromyzidae) are a diverse family of small-bodied insects that feed on living plant tissues as larvae.  Various species in this family are considered globally invasive and have caused great agricultural economic losses.  In China, economically important vegetable crops have been seriously damaged by these pest insects, especially by species of the genus Liriomyza.  However, these species are difficult to differentiate because of their morphological similarities, and the Chinese fauna remains poorly known.  To explore the relevant pest species in China and their phylogeny, agromyzid leafminers were collected from 2016 to 2019, and identified based on morphological characteristics and DNA barcodes.  In total, 27 species from five genera of Agromyzidae were sampled and identified, including 16 species of Liriomyza.  Both mitochondrial and nuclear genes were used to reconstruct their phylogenetic relationships and estimate the divergence time.  Highly congruent and well-supported phylogenetic trees were obtained using the Bayesian inference and maximum-likelihood methods.  This analysis revealed two main clades in Liriomyza, and clade 2 was inferred to have diverged from clade 1 approximately 27.40 million years ago (95% highest posterior density: 23.03–31.52 million years ago) in the Oligocene.  Differences were observed in the distribution patterns and host associations between the Liriomyza clades.  Clade 2 species are distributed in cool, high-latitude environments, suggesting that they may have evolved into a cool-adapted lineage.

China is one of the countries in the world that is severely damaged by crop diseases, pests, and weeds.  There are more than 1 700 species of agricultural pests occurring annually, 53 of which are on the list of the 100 worst pests in the world (Chen and Wang 2014; Wu 2018).  Currently, China is still greatly challenged by a growing problem of agricultural pests that threaten the economy and health and pose ecological risks under the conditions of global climate change, economic integration, crop structure adjustment and so on.  Plant protection against crop diseases, insect pests and noxious weeds is necessary to ensure high-quality crop production and food safety.  However, traditional strategies of plant protection have mainly involved chemical pesticides, which bring a series of other problems, such as pesticide residues, pest resistance and resurgence.  During the past decades, Chinese scientists have been committed to
research on developing new plant protection methods through integrated pest management (IPM) in a safe, cost-effective and sustainable manner.  In this field, we organized this special issue to provide the most updated theories and technologies of plant protection.

There are 21 manuscripts accepted for publication in this special issue, including 13 reviews and eight research articles.  The 13 reviews involved a variety of relevant disciplines, such as insect ecology and molecular biology, phytopathology, biological invasions and pest management science.  Three papers documented the progress in insect ecology and molecular biology.  Bao and Zhang (2019) reported the recent molecular research in Nilaparvata
lugens on its endosymbionts, virus transmission, insecticide resistance, and host interaction.  Li et al. (2019) gave an overview of the discovery, biogenesis and functions of four kinds of ncRNAs, including miRNA, piRNA, circRNA and lncRNA in insects, and Xue et al. (2019) investigated thermal adaptation of Drosophila from three aspects of behavior, plastic responses and micro-evolution under global climate change.  Two papers investigated the threats from pathogenic microbes, Chinese wheat mosaic virus and fire blight disease, to wheat and pear production, respectively, in China, and provided cost-effective countermeasures to control these diseases in the future (Guo et al. 2019; Zhao Y Q et al. 2019).  Four other papers mainly focused on the introduction routes, expansion process (adaptation and interactions), ecological effects and control of invasive insects, including Bemisia tabaci, Phenacoccus solenopsis, Bactrocera dorsalis and Solenopsis invicta (Chu et al. 2019; Liu H et al. 2019; Tong et al. 2019; Wang et al. 2019a).  Additionally, there were three papers that provided sound prospects for improving the strategies currently employed in agricultural control, biological control and chemical control (Lu et al. 2019; Pan et al. 2019; Wang et al. 2019b).  Finally, Liu (2019) evaluated the current status and challenges of rodent biology and management in China.  

The eight research articles mainly involved the three aspects of reproductive biology and chemical ecology of pests, safety assessments of genetically modifed crop and weed control (He et al. 2019; Huang et al. 2019; Liu  Y M et al. 2019; Lü et al. 2019; Muhammad et al. 2019; Xiu et al. 2019; Zhao C C et al. 2019; Zheng et al. 2019).  Among those, there were two papers that explored the tradeoffs between reproduction and energy reserves (Huang et al. 2019; Zhao C C et al. 2019).  Liu Y M et al. (2019) proved that Bt maize expressing cry1Ab/2Aj or cry1Ac genes posed a negligible risk to adult Chrysoperla sinica.  In addition, Muhammad et al. (2019) and He et al. (2019) evaluated the effects of weed control under wheat stubble management and different culture patterns, respectively.

I believe these articles in this special issue should be of broad interest to a diverse audience at multiple levels in the areas of plant protection, and they are well-suited for the readers of Journal of Integrative Agriculture.  I sincerely appreciate all the authors who gave their high-quality contributions and efforts to this special issue.

The rapid development of omics provides new technologies and methodologies for the study of invasion biology. Agricultural Genomics Institute at Shenzhen (CAAS-AGIS) and Institute of Plant Protection, Chinese Academy of Agricultural Sciences (CAAS-IPP) initiated the “IAS1000 project” (A genome project of 1000 invasive alien species) and established the “IAS1000 alliance” in Shenzhen on November 14, 2018. Via deep-mining of omics data, the project aims for better understanding the ecological processes and molecular mechanisms of biological invasion, and developing new technologies and products for prevention and management of invasive alien species. Up to now, there have been more than 40 research institutes, universities and enterprises participating in this project, forming an omics team with multi-disciplinary members.

The main tasks of “IAS1000 project” include: (i) building a global collaboration platform for an in-depth research on molecular mechanisms of invasiveness; (ii) developing new technologies and products for prevention and control of invasive alien species, including RNA interference, gene editing, molecular pesticides with specific target carried by new physical/chemical materials, intelligent recognition of molecular odor, utilization of molecule-induced immunity, creation of new vaccines, and the restorer of soil ecological network; (iii) cultivating new elite talents in the integrated subjects encompassing omics, invasion biology, entomology and botany, etc.

   The whitefly Bemisia tabaci is a species complex, of which two invasive species, called MEAM1 and MED whiteflies, have invaded many parts of the world in the past 30 years and replaced native whitefly populations in many regions of invasions including many areas in China. One of the possible reasons for the invasion is that MEAM1 and MED whiteflies are more fecund than the native species. However, factors that affect reproduction and the molecular mechanism of vitellogenesis among various B. tabaci cryptic species are not clearly known. In this study, cDNAs of vitellogenin (Vg) genes were sequenced from native B. tabaci Asia II 1 and invasive B. tabaci MED in China. The deduced amino acid sequences were 2 182 residues in Asia II 1 and 2 217 residues in MED. Compared to the Vg gene cDNA sequence of Asia II 1 species, the Vg gene in MED could be cleaved at least into four subunits, with deduced molecular weight of 50, 90, 150 and 190 kDa, respectively. However, only two different subunits were cleaved between residues 459 and 460 in the Asia II 1. In addition, more than two serine-rich stretches located in both the N-terminal and the C-terminal region in invasive species. More GHN domains were revealed only in the N-terminal region of B. tabaci MED. Vg gene expression pattern was characterized using quantitative real-time (qRT)-PCR to compare the dynamic of vitellogenin gene mRNA level. Vg gene transcription reached the peak level at 13 d after eclosion in B. tabaci Asia II 1, 3 d later than that in MED and another invasive species of the B. tabaci complex MEAM1. We assumed that the present difference of Vg gene expression pattern is due to the different regulation pattern of vitellogenesis among species of the B. tabaci complex. These results provide useful information to reveal the mechanisms of reproduction in whitefly species complex.

    Currently, insecticides are considered as the primary approach for controlling western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). However, the heavy use of insecticides resulted in high insect resistance and serious environmental pollution. Given its characteristics of ease of operation and environmental friendliness, insect control using high temperature is receiving considerable renewed research interest. However, although the combination of insecticides and high temperature to control F. occidentalis has been studied before, few studies have focused on the short-term effect of such treatment. In a laboratory study, F. occidentalis adults and second-instar nymphs were exposed to 45°C for 2 h. Then, their susceptibility to acetamiprid, spinosad, methomyl, and beta-cypermethrin was tested after different periods of recovery time (2–36 h). Additionally, the specific activity of three detoxification enzymes (esterase, glutathione S-transferase, and cytochrome p450 (CYP) monooxygenase) of the treated insects was determined. The results indicated that the fluctuation of susceptibility to insecticides and detoxification enzyme activity during F. occidentalis recovery from heat shock are related. Furthermore, several recovery time points (2, 30, and 36 h) of significant susceptibility to four tested insecticides compared with the control were found during the treatment of adults that were heat-shocked. Recovery time points of higher susceptibility compared with the control depended on different insecticides during the second-instar nymph recovery from heat shock. Interestingly, the fluctuation of CYP monooxygenase activity exhibited a trend that was similar to the fluctuation of susceptibility to insecticides (especially spinosad) during the recovery from heat shock of adults. In addition, the glutathione S-transferase and CYP monooxygenase activity trend was similar to the trend of susceptibility to spinosad during the recovery from heat shock of second-instar nymphs. Our results provide a new approach for controlling F. occidentalis using the combined heat shock and insecticide. This effectively enhances the control efficiency of heat shock and significantly reduces the application of insecticides

Exotic plant invasion presents a serious threat to native ecosystem structure and function. Little is known about the role of soil microbial communities in facilitating or resisting the spread of invasive plants into native communities. The purpose of this research is to understand how the invasive annual plant Ambrosia artemisiifolia L. facilitates its competition capacity through changing the structure and function of soil microbial communities. The soil characteristics of different areas invaded by A. artemisiifolia were examined. Greenhouse experiments were designed to assess the effect of A. artemisiifolia invasion-induced changes of soil biota on co-occurring plant growth, and on the interactions between A. artemisiifolia and three co-occurring plant species. The results showed that the soil organic C content was the highest in heavily invaded sites, the lowest in native plant sites, and intermediate in newly invaded sites. Soil available N, P and K concentrations in heavily invaded site were 2.4, 1.9 and 1.7 times higher than those in native plant soil, respectively. Soil pH decreased as A. artemisiifolia invasion intensity increased, and was lower in invaded sites (heavily invaded and newly invaded) than in native plant sites. The soil microbial community structure was clearly separated in the three types of sites, and A. artemisiifolia invasion increased anaerobe, sulfate-reducing bacteria and actinomycete abundance. Soil biota of invaded sites inhibits growth of co-occurring plants (Galinsoga parviflora Cav., Medicago sativa L. and Setaria plicata (Lam.) T. Cooke.) compared to soil biota from un-invaded sites, but facilitates A. artemisiifolia growth and competition with co-occurring plants. A. artemisiifolia biomass was 50-130% greater when competing with three co-occurring plants, compared to single-species competition only (invasion by A. artemisiifolia alone), in heavily invaded soil. Results of the present study indicated that A. artemisiifolia invasion alters the soil microbial community in a way that favors itself while inhibiting native plant species, with measurable effects on performance of co-occurring plants.

Coexisting natural enemies that share a common host resource in the same guild usually exhibit variation in their life history traits, due to their need to share a similar ecological niche. In this study, we compared the immature development times and adult life history traits of two coexisting, host-feeding parasitoids, Diglyphus isaea Walker and Neochrysocharis formosa Westwood (Hymenoptera: Eulophidae), of which both attack larvae of the same agromyzid leafminers. These two species are both synovigenic, idiobiont parasitoids, whose adults consume host fluids (“host feeding”) and lay anhydropic eggs. Of the two, D. isaea has a larger body but little or no initial egg load, and engages in similar lifetime host-feeding events. However, it achieves higher fecundity, longer adult longevity, and higher host suppression ability than N. formosa, which has a smaller body and higher initial egg load. Although D. isaea engages in similar lifetime host-feeding events with N. formosa, all of its gains in life history traits per host-feeding event of D. isaea were larger than those of N. formosa. The age-specific fecundity and host mortality curves of N. formosa were more skewed in early life than those of D. isaea. In addition, the ovigeny index of N. formosa was negatively correlated to body size. Our results confirmed that two coexisting parasitoids, which share the same host resource, show different immature development patterns and life history traits, suggesting that different resource allocation mode could be a general rule of coexisting species sharing the same habitat or host.

The density seasonal dynamics of Bemisia tabaci MED were evaluated over two years in a cotton-growing area in Langfang, Hebei Province, northern China on cotton (Gossypium hirsutum L.) and six other co-occurring common plants, common ragweed (Ambrosia artemisiifolia L.), piemarker (Abutilon theophrasti Medicus), sunflower (Helianthus annuus L.), sweet potato (Ipomoea batatas L.), soybean (Glycine max L.), and maize (Zea mays L.). The whitefly species identity was repeatedly tested and confirmed; seasonal dynamics on the various host plants were standardized by the quartile method. B. tabaci MED appeared on weeds (the common ragweed and piemarker) about 10 days earlier than on cotton, or the other cultivated plants. The peak population densities were observed over a span of 2 to 3 weeks on cotton, starting in early (2010) or mid-August (2011). The common ragweed growing adjacent to cotton supported the highest B. tabaci densities (no. on 100 cm2 leaf surface), 12-22 fold higher than on cotton itself. Sunflower supported more B. tabaci than the other plants, and about 1.5-2 fold higher than cotton did. Our results indicate that weeds (esp. the common ragweed) around cotton fields could increase the population density of B. tabaci MED on cotton, while sunflower could act as a trap crop for decreasing pest pressure on cotton.

Thermal adaptation plays a fundamental role in shaping the distribution and abundance of insects, and heat shock proteins (Hsps) play important roles in the temperature adaptation of various organisms. To better understand the temperature tolerance of the indigenous ZHJ2-biotype of whitefly Bemisia tabaci species complex, we obtained complete cDNA sequences for hsp90, hsp70, and hsp20 and analyzed their expression profiles under different high temperature treatments by real-time quantitative polymerase chain reaction. The high temperature tolerance of B. tabaci ZHJ2-biotype was determined by survival rate after exposure to different high temperatures for 1 h. The results showed that after 41°C heat-shock treatment for 1 h, the survival rates of ZHJ2 adults declined significantly and the estimated temperature required to cause 50% mortality (LT50) is 42.85°C for 1 h. Temperatures for onset (Ton) or maximal (Tmax) induction of hsps expression in B. tabaci ZHJ2-biotype were 35 and 39°C (or 41°C). Compared with previous studies, indigenous ZHJ2- biotype exhibits lower heat temperature stress tolerance and Ton (or Tmax) than the invasive B-biotype.