Search

Simple Summary: The pea aphid, Acyrthosiphon pisum, is a serious pest of legume crops that can produce winged and wingless offspring in response to the environmental conditions. We found that, under crowded conditions, the red morph A. pisum produced more winged offspring than the green morph. The signaling pathways involved in aphid wing determination also play important roles in regulating growth, development, and metabolism. Thus, we examined the association between the wing-producing ability and the growth rate, development time, reproductive capacity, and energy metabolism in these two color morphs. The growth rate, levels of glycogen and triglycerides in red morphs were significantly higher than those of green morphs, whereas green morphs produced more offspring. Red morphs also consumed more triglycerides during starvation and had stronger starvation tolerance. Furthermore, the expression levels of genes involved in the insulin pathway, glycolysis, and lipolysis in red aphids were also higher. These results suggest that the wing-producing ability of the pea aphid may be associated with its growth and metabolism. The pea aphid, Acyrthosiphon pisum, is a major pest of legume crops, exhibiting distinct polymorphism in terms of wings and body color. We found that, under crowded conditions, the red morph A. pisum produced more winged offspring than the green morph. The signaling pathways involved in aphid wing determination, like insulin and ecdysone, also play important roles in regulating growth, development, and metabolism. Thus, here, we examined the association between the wing-producing ability and the growth rate, development time, reproductive capacity, and energy metabolism in these two color morphs. The growth rate of red morphs was significantly higher than that of green morphs, whereas green morphs produced more offspring during the first 6 days of the adult stage. Red morphs accumulated higher levels of glycogen and triglycerides and consumed more triglycerides during starvation; however, green aphids consumed more trehalose during food deprivation. Red aphids exhibited stronger starvation tolerance, possibly due to their higher triglyceride catabolic activity. Furthermore, the expression levels of genes involved in the insulin pathway, glycolysis, and lipolysis in red aphids were higher than those in green aphids. These results suggest that the wing-producing ability of the pea aphid may be associated with its growth and metabolism, which may be due to the shared regulatory signaling pathways. [ABSTRACT FROM AUTHOR]

Simple Summary: The fall armyworm, Spodoptera frugiperda (Lepidoptera, Noctuidae), invaded China in 2019. The species has been established as a year-round breeding population in most of the southern provinces which are the main winter maize planting areas. The effect of rising nighttime temperatures, driven by the changing climate in this region, on the growth and development of S. frugiperda is unclear. Results of this study show that the survival rate of larvae and pupae significantly declined with daytime temperatures declining and the nighttime temperature range increasing. Development rate accelerated along with the increasing daytime temperatures and nighttime temperatures, except for the intermediate treatments (daytime temperature 24 °C and diurnal range from 2–6 °C). Predictions of FAW development and warnings to local farmers need to be adjusted to take into account more rapid development when nighttime temperatures increase in the warming climate. The Fall Armyworm, Spodoptera frugiperda (Lepidoptera, Noctuidae), is a serious migratory pest. After invading China in 2019, the species was established as a year-round breeding population in most of the southern provinces. The area of winter maize in this region has been increasing due to the huge demand of fresh maize consumption, which is potentially at risk from this invasive pest, although the growth and development of S. frugiperda in the region's changing climate is unclear, particularly with rising temperatures at night. Here, we used the highest daytime temperatures of 27 °C, 24 °C, 20 °C and decreased these by 2, 4 and 6 °C to reflect the range of nighttime temperatures indicative of winter conditions in a warming climate to evaluate the effect of increasing night temperatures on the growth and development of S. frugiperda. Results show that the survival of larvae and pupae significantly declined with daytime temperatures declining and the nighttime temperature range increasing. Significant developmental effects were observed across all daytime–nighttime temperature treatments, except for adults. Additionally, there were significant interaction effects for all stages, except the egg stage, and generation time. The development rate increased with the increasing daytime temperatures and nighttime temperatures, except for the intermediate treatments (Group II). The uniformity of pupation and emergence times were higher under high daytime temperatures and nighttime temperature treatments. Predictions of FAW development and warnings to local farmers need to be adjusted to take into account the more rapid development when nighttime temperatures increase in the warming climate. These results will support decision makers in developing long-term management strategies for FAW in southern China. [ABSTRACT FROM AUTHOR]

The globose scale (GS) (Sphaerolecanium prunastri Boyer de Fonscolombe) is a sucking insect that feeds on saps of wild apricot tree (Prunus armeniaca L.) in the Xinjiang Uygur Autonomous Region of northwestern China. It feeds on branches of wild apricot leading to poor growth, leaf yellowing and leaf drop, and sometimes mortality. Since the initial infestation in 2018, all the main valleys of wild apricot trees have been affected, but there is little research on the host's physiological response to GS infestation. We measured the differences in growth between infested and non-infested wild apricots. The results showed that the diameter of shoot branches, the fresh weight, dry weight, length, width, area, and chlorophyll content of leaves, and the longitudinal diameter of fruit, were all significantly less for infested wild apricot trees than for un-infested wild apricot. The branch length of shoots, cross diameter, and weight of fruit also decreased, although the differences were not significant. Overall, GS infestation significantly reduced the growth of wild apricot trees. [ABSTRACT FROM AUTHOR]

This research aimed to evaluate the occurrence of three significant pests, namely the apple ermine moth (Y. malinellus Zell.), the rosebush leaf roller (A. rosana L.), and the hawthorn leaf roller (C. crataegana Hb.), commonly found in Sievers apple trees. The research was conducted within the Ili-Alatau state national natural park, focusing on populations of the Sievers apple tree on the northern slope of the Trans-Ili Alatau mountain range. The study revealed varying pest abundances across different monitoring sites within the park. The apple ermine moth (Y. malinellus Zell.) exhibited lower occurrence compared to A. rosana L. and C. crataegana Hb. The Aksai and Kuznetsov Gorge populations of the Sievers apple tree showed higher susceptibility to the ermine moth. The rosebush leaf roller (A. rosana L.) was dominant in the Aksai and Oi-Zhailau populations, while the hawthorn leaf roller (C. crataegana Hb.) exhibited higher abundance in several monitoring sites. Phenological studies revealed that Y. malinellus Zell. have a life cycle of one year, the developmental stages of A. rosana L. last for approximately 9–10 months, and the life cycle of C. crataegana Hb. is also one year. The data obtained allowed us to assess pest status, which will hopefully help in developing protective measures for suppressing their outbreak in the region. [ABSTRACT FROM AUTHOR]

Rice dwarf virus (RDV) is transmitted by insect vectors Nephotettix virescens and Nephotettix cincticeps (Hemiptera: Cicadellidae) that threatens rice yield and results in substantial economic losses. RDV induces two volatiles ((E)-β-caryophyllene (EBC) and 2-heptanol) to emit from RDV-infected rice plants. However, the effects of the two volatiles on the olfactory behavior of both non-viruliferous and viruliferous N. virescens are unknown, and whether the two volatiles could facilitate the spread and dispersal of RDV remains elusive. Combining the methods of insect behavior, chemical ecology, and molecular biology, we found that EBC and 2-heptanol influenced the olfactory behavior of non-viruliferous and viruliferous N. virescens, independently. EBC attracted non-viruliferous N. virescens towards RDV-infected rice plants, promoting virus acquisition by non-viruliferous vectors. The effect was confirmed by using oscas1 mutant rice plants (repressed EBC synthesis), but EBC had no effects on viruliferous N. virescens. 2-heptanol did not attract or repel non-viruliferous N. virescens. However, spraying experiments showed that 2-heptanol repelled viruliferous N. virescens to prefer RDV-free rice plants, which would be conducive to the transmission of the virus. These novel results reveal that rice plant volatiles modify the behavior of N. virescens vectors to promote RDV acquisition and transmission. They will provide new insights into virus–vector–plant interactions, and promote the development of new prevention and control strategies for disease management. [ABSTRACT FROM AUTHOR]

Simple Summary: Maximizing the combination of biological control by natural enemies and plant resistance is a key strategy for controlling aphids in various crop systems. In our study, some alfalfa cultivars were found to have resistance to the pea aphid, Acyrthosiphon pisum, a dominant pest in alfalfa fields in northwestern China. In addition, natural enemies were able to significantly suppress this aphid, regardless of the resistance level of the nine cultivars tested. Moreover, the biological control efficacies of predators, parasitoids, and mixed populations of natural enemies were 85%, 42%, and 88%, respectively. Conservation of natural enemies in the field is an ecologically sound and efficient approach to the management of the pea aphid in alfalfa crops. The pea aphid, Acyrthosiphon pisum Harris, is a major pest of alfalfa in northwestern China. However, the roles of different groups of natural enemies in combination with aphid-resistant cultivars in the suppression of the pea aphid have not been clarified under field conditions. In this study, we used experimental cages to better understand the top-down (natural enemies) and bottom-up (nine alfalfa cultivars) biological processes, as well as the individual roles of the two processes, in the control of the pea aphid. There was a significant difference in resistance among cultivar classes revealed when natural enemies were excluded. The functional contribution of top-down suppression was higher than the bottom-up process, with natural enemies significantly suppressing aphid populations, regardless of the resistance level of different alfalfa cultivars. The mean biological efficacies of predators, parasitoids, and mixed populations of natural enemies were 85%, 42%, and 88%, respectively. Overall, our study indicated that natural enemies play a critical role in suppressing aphid populations, especially in the summer, whereas cultivar resistance did not combine effectively with natural enemies to inhibit the growth of aphids. Conservation biological control (CBC) can be implemented in the alfalfa production regions in northwestern China to reduce the overreliance on insecticides for the control of pests and mitigate their harmful effects on humans, ecosystems, and biodiversity. [ABSTRACT FROM AUTHOR]

Simple Summary: In this article, we studied the interactions between the invasive thrips pest Frankliniella occidentalis (WFT) and a native thrips Frankliniella intonsa (IFT) in China, where they co-exist on crop plants and WFT seems to outcompete IFT. In laboratory bioassays we focused on the reproductive mode of the thrips (sexual or parthenogenic), and the presence of a sugar source (honey or flowers), both variables that change over time during pest colonisation of a crop. Our results suggest that in the early stages of F. occidentalis invasion, the provision of honey (flowering) promotes this pest's population development. This research will inform effective strategies for the management of F. occidentalis invasion and help reduce subsequent crop damages. Background: Flower thrips (Frankliniella intonsa, IFT) and west flower thrips (Frankliniella occidentalis, WFT) are often found together on the host plant in China. WFT is an important invasive species that seems to outcompete the native IFT. In order to clarify the interspecific competitions between the two thrips, this study measured the population development of IFT and WFT under sexual and parthenogenetic reproductive modes on two hosts (fresh lentil bean pods with/without honey and pepper plants at seedling/flowering stages) in the laboratory. Results: When reared on fresh lentil bean pods (with/without honey), WFT population size was lower in mixed species populations compared to single species populations but the presence of WFT had nor negative effect on IFT population size. These results were dependent of the reproductive mode. When honey was supplied, the ratio of female-to-male in the progeny of WFT produced under sexual reproductive mode increased significantly in the presence of IFT. On pepper seedlings, mixed populations were more favorable to the population development of IFT at the seedling stage, but more favorable to WFT at the flowering stage. Conclusions: In the early stage of WFT invasion and colonization, the emergence of flowering and honey (nectar) sources may have a positive effect on the population development of WFT. [ABSTRACT FROM AUTHOR]

Simple Summary: Aphis craccivora Koch (cowpea aphid, CPA), Acyrthosiphon pisum Harris (pea aphid, PA) and Therioaphis trifolii Buckton (spotted alfalfa aphid, SAA) are the three species of devastating pests on alfalfa in China. A study was conducted in the laboratory for identification and characterization of resistance to these three aphids among 16 of the main alfalfa cultivars planted in China. Resistance was indicated by antibiosis, antixenosis, and measuring feeding behavior using EPG (electrical penetration graph). The results indicated that different alfalfa cultivars have significantly different resistance levels to a particular species of aphid, and the same alfalfa variety also has different resistance to the three aphid species. Specifically, we evaluated the resistance of different alfalfa cultivars to CPA, which can help us for further study on the defense mechanism against CPA and for better management of this pest. Aphids on alfalfa (Medicago sativa) including Aphis craccivora Koch (cowpea aphid, CPA), Acyrthosiphon pisum Harris (pea aphid, PA) and Therioaphis trifolii Buckton (spotted alfalfa aphid, SAA) cause significant yield losses worldwide. In this experiment, the development of these three species of aphids on 16 alfalfa cultivars was compared. The results showed that the plant cultivar had a significant influence on the development of aphids as there are significant differences in the body weight of aphids reared on different alfalfa cultivars. In addition, antibiosis between the alfalfa cultivars Pegasis and Gannong NO.9 and the three species of aphids was evaluated by measuring aphid body weight and fecundity. Antixenosis was measured using choice tests, and feeding behavior was quantified using electrical penetration graphs (EPG). The Pegasis cultivar was observed to have both antibiosis and antixenosis effects with CPA, but was susceptible to PA and SAA compared with the Gannong NO.9 cultivar. CPA had less mean body weight, less fecundity, and shorter feeding time on the Pegasis cultivar, and preferred to settle on Gannong NO.9 cultivar. In contrast, Gannong NO.9 exhibits antibiosis and antixenosis to PA and SAA compared with Pegasis, as shown by lower body weight, lower fecundity and chose to settle less often, but EPG data showed that PA and SAA showed no different significance in feeding behavior between Pegasis and Gannong NO.9. [ABSTRACT FROM AUTHOR]

Simple Summary: Bemisia tabaci Middle East–Asia Minor I (MEAM1) is a widely distributed invasive agricultural pest that causes extensive damage to agricultural, horticultural, and ornamental crops. Laccase2 (Lac2), a phenol oxidase, plays an important role in cuticle tanning of some insects. However, the function of Lac2 in whitefly remains unclear. In this study, we identified a BtLac2 gene in MEAM1 that is expressed in all developmental stages, and its expression in the cuticle is especially high. Knockdown of BtLac2 in nymphs produced thinner and fragile cuticles, which significantly increased the mortality rate and extended the development duration of nymphs, as well as further decreasing the emergence rate of adults. Overall, BtLac2 plays an important role in cuticle hardening of whitefly, suggesting a potential management strategy using RNAi to knock down BtLac2 expression. Cuticle sclerotization is critical for insect survival. Laccase2 (Lac2) is a phenol oxidase that plays a key role in cuticle formation and pigmentation in a variety of insects. However, the function of Lac2 in whitefly, Bemisia tabaci, remains unclear. In this study, we identified a BtLac2 gene in B. tabaci MEAM1 and found that BtLac2 was expressed in all stages. It was highly expressed in the egg stage, followed by nymph and adult. Moreover, the expression of BtLac2 was higher in the cuticle than in other tissues. Knockdown of BtLac2 in nymphs produced thinner and fragile cuticles, which significantly increased the mortality rate, extended the development duration of nymphs, and decreased the emergence rate of adults. This result demonstrates that BtLac2 plays an important role in the cuticle hardening of B. tabaci and suggests a potential management strategy using RNAi to knock down BtLac2 expression. [ABSTRACT FROM AUTHOR]

Simple Summary: Cotton aphid (Aphis gossypii Glover) (Homoptera: Aphididae) is a major pest of cotton and other cash crops across cotton-growing areas in China. The decision to spray insecticide or rely on biocontrol and delay spraying is often a dilemma in cotton-growing regions. In this study, we used a laboratory experiment and a caged experiment in a garden as well as modeling to understand the ratio of prey/predator for the abovementioned decision making. We suggested that the ratio of prey/predator should be less than 450 for the effective biocontrol of cotton aphid at cotton seedling stage. This finding can improve the efficiency of larger-scale cotton aphid management in China. The decision to delay or cancel spraying insecticides against pest aphids is dependent on the ratio of prey/predator, which reflects how well the predator can suppress the aphid population increase in the field. It is challenging to estimate the ratio of prey/predator due to the multiple factors involved in the interaction between prey and predator. Cotton aphid (Aphis gossypii Glover) is a serious pest, widely distributed in cotton-growing areas around the world. We combined different ratios of aphids with aphid oligophagous ladybird beetles (Coccinella septempunctata Linnaeus) under laboratory and garden conditions to investigate the critical threshold for prey/predator which effectively reduced the cotton aphid population increase. Two kinds of modeling were developed to understand the relationships between the ratio of prey/predator and the PGR (population growth rate), and with the effectiveness of biocontrol (EBC). We found the critical values of PGR should be less than −0.0806 (predators artificially released after 5 days) and then less than −0.075 (predators released after 10 days) if EBC is less than 50%. We recommend that the ratio of prey/predator should be less than 450 for the effective biocontrol of cotton aphids at the cotton seedling stage. These values can be reference indices for the management of aphids in mid-summer. [ABSTRACT FROM AUTHOR]

Simple Summary: Walnut aphids are major pests of walnut orchards with few commercially available natural enemies except parasitoids. The predatory bug (Orius sauteri) was assessed as a potential biological control agent against two walnut aphid species. This bug has a strong capacity for consuming both aphid species. Biocontrol efficacy of O. sauteri for each species was high (more than 70%), but declined about 20% when both aphid species present on the same leaf together. This might be due to the competition among two species of aphids tested. Three statistical approaches were employed to show that O. sauteri is a promising biocontrol agent. The commercial release of O. sauteri should be considered for the coexisting aphids in walnut orchards to promote economic and environmental benefits. Walnut aphids are major pests of walnut production with few commercially available natural enemies. We conducted laboratory and field experiments to evaluate the potential of Orius sauteri Poppius (Anthocoridae), a predatory bug, as a biological control agent against two walnut aphid species: the dusky-veined aphid (Panaphis juglandis Goeze) and the walnut aphid (Chromaphis juglandicola Kaltenbach). Both species co-occur on walnut trees; P. juglandis is distributed on the upper surface (adaxial) of leaves while C. juglandicola is found on the lower surface (abaxial) of leaves. Based on functional response experiments, O sauteri had a strong capacity for consuming both aphid species. Biocontrol efficacy of O. sauteri for each species in the laboratory and field experiments was high, 77% for P. juglandis and 80% for C. juglandicola, regardless if one or two predators being present. However, biocontrol efficacy declined 15–25% for C. juglandicola and 20–50% for P. juglandis when both aphid species were present on the same leaf. The efficacy of O. sauteri under (semi)-field conditions gave similar findings based on the percentage reduction of aphids and change in population growth rates of aphids. The reduced biocontrol efficacy of the predatory bug against mixed species populations of aphids can be explained by competition between the aphid species and differences in their preferred location on leaves. Our experiments showed that O. sauteri is a promising biocontrol agent, but biocontrol efficacy may decline when both aphid species are present on walnut trees. This should be considered in the commercial release of O. sauteri in walnut orchards to promote economic and environmental benefits of walnuts production. [ABSTRACT FROM AUTHOR]

The South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), a destructive pest on tomato, has invaded most Afro-Eurasian countries. Recently invaded by the pest, most tomato crops in greenhouses and open fields in Tajikistan are currently suffering major damage. While failure in management using chemical insecticide has been frequently observed, alternative options such as biological control is urgently needed. In this study, we evaluated the effectiveness of the common green lacewing Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) against T. absoluta. In controlled laboratory conditions, C. carnea showed high predation rate on both T. absoluta eggs (i.e., 36 ± 2 eggs within 24 h and 72 ± 4 eggs within 48 h) and larvae, especially it can attack the larvae both inside and outside the leaf galleries (i.e., an average of 22% of the larvae was killed inside, and an average of 35% was killed outside). In a cage exclusion experiment, T. absoluta showed relatively low larval density in the cages with pre-fruiting release of C. carnea, whereas the larval density was four to six times higher in the "no release" cages. In the "post-fruiting release" cages, the pest population that had already built up during the pre-fruiting stage eventually crashed. In an open-field experiment, the tomato crops in control plots were fully destroyed, whereas low levels of larvae density and damage were observed in the biocontrol plots. Moreover, the field release of C. carnea resulted in significantly higher tomato yield than those without release, despite no differences between the "pre-fruiting release" and "post-fruiting release" treatments. We conclude that the local commercial biocontrol agent C. carnea could be promising for the management of T. absoluta in Tajikistan. It is also one of the first reports showing the management of T. absoluta using a lacewing species. The effectiveness should be validated by further field trials in larger area of commercial crops and various locations. [ABSTRACT FROM AUTHOR]

Malus sieversii (Ledeb.) M. Roem is a tertiary relict tree species and a rare and valuable resource for germplasm conservation. Since 1995, its wild forest has been severely destroyed by a devastating wood-boring beetle Agrilus mali Matsumura (Coleoptera: Buprestidae) in Xinjiang Uygur Autonomous Region, China. Where it invaded, this beetle infested more than 95% of the forests, and 80% of wild apple trees were reported dead in the hotspots. The physiological damage by A. mali infestation and their causality to tree death remain unclear. In this study, we attempted to explain the wild apple dieback from plant physiological perspectives, based on the hypothesis that the more damage M. sieversii suffered from the infestation of A. mali, the less water and fewer nutrients it could utilize. The study was conducted on trees with different extents of damage in wild apple forests over a large scale during 2016 and 2017. The stable carbon isotope ratio in leaves was analyzed to indicate tree water stress status. Total N, total P, total K, Ca2+ and Mg2+ were analyzed to reflect plant mineral nutrient status. The extent of damage was significantly associated with the leaf stable carbon isotope ratio in the drier year of 2016, but not significantly in 2017 with heavy rainfall in spring. The mineral nutrient contents of leaves were not significantly different among the four damage rankings in either year. The water stress experienced by M. sieversii was aggravated by the damage caused by A. mali, especially in a drought year, and indicates that the long-term water deficit caused by A. mali infestation may be the key factor leading to the decline of wild apple forests. The finding suggests the necessity of aerial irrigation for sustainable integrated pest management in wild apple trees. [ABSTRACT FROM AUTHOR]