Wheat cultivars and natural-based substances: Impacts on epidemiological parameters of yellow dwarf disease

For many years, control methods against aphid-transmitted barley/cereal yellow dwarf viruses (B/CYDV) in cereal fields were mainly based on the use of neonicotinoid (NNI)-coated seeds. The ban of NNI by the EU in 2018 has reinforced the interest of the scientific community in the characterization of genetic resources and biological protections to find alternatives to chemicals for the management of B/CYDV. Eleven BYDV-susceptible wheat varieties were tested using a set of experimental procedures to evaluate their potential to alter parameters linked to the biology of aphids (Rhopalosiphum padi) and spread of virus (BYDV-PAV). Moreover, two natural-based substances (azadirachtin and mineral oil) were tested for their impact on the ability of aphids to survive, colonize and transmit the virus. Results showed that the 11 genotypes tested have a level of susceptibility to virus infection similar to the susceptible reference cv. Rubisko. However, when characterization focused on virus load, latency period and aphid fecundity, partial resistance phenotypes were observed for some cultivars. Furthermore, azadirachtin increased aphid mortality and decreased aphid fecundity. Thus, in addition to genes described for their ability to limit B/CYDV infections, the genetic backgrounds of B/CYDV-susceptible wheat cultivars and azadirachtin-based treatment should be considered for future management strategies against yellow dwarf disease.     

Toxicities and sublethal effects of seven neonicotinoid insecticides on survival, growth and reproduction of imidacloprid-resistant cotton aphid, Aphis gossypii

BACKGROUND: Imidacloprid has been a major neonicotinoid insecticide for controlling Aphis gossypii (Glover) (Homoptera: Aphididae) and other piercing–sucking pests. However, the resistance to imidacloprid has been recorded in many target insects. At the same time, cross‐resistance of imidacloprid and other insecticides, especially neonicotinoid insecticides, has been detected. RESULTS: Results showed that the level of cross‐resistance was different between imidacloprid and tested neonicotinoid insecticides (no cross‐resistance: dinotefuran, thiamethoxam and clothianidin; a 3.68–5.79‐fold cross‐resistance: acetamiprid, nitenpyram and thiacloprid). In the study of sublethal effects, imidacloprid at LC₂₀ doses could suppress weight gain and honeydew excretion, but showed no significant effects on longevity and fecundity of the imidacloprid‐resistant cotton aphid, A. gossypii. However, other neonicotinoid insecticides showed significant adverse effects on biological characteristics (body weight, honeydew excretion, longevity and fecundity) in the order of dinotefuran > thiamethoxam and clothianidin > nitenpyram > thiacloprid and acetamiprid. CONCLUSION: The results indicated that dinotefuran is the most effective insecticide for use against imidacloprid‐resistant A. gossypii. To avoid further resistance development, the use of nitenpyram, acetamiprid and thiacloprid should be avoided on imidacloprid‐resistant populations of A. gossypii. Copyright © 2011 Society of Chemical Industry     

Insecticide resistance profiles can be misleading in predicting the survival of Myzus persicae genotypes on potato crops following the application of different insecticide classes

BACKGROUND: The accuracy of predicting the survival of insecticide‐resistant aphids following the application of commonly used insecticides from the carbamate, the pyrethroid, a mix of the two or the neonicotinoid chemical classes was evaluated in a potato field in Scotland. Equal proportions of five genotypes of the peach‐potato aphid, Myzus persicae (Sulzer), with none, resistance to dimethyl‐carbamates, resistance to pyrethroids or combinations conferring resistance to both chemical classes were released into potato field plots. The insecticides were sprayed separately onto these plots, the aphid populations were analysed after 6–8 days and the process repeated. RESULTS: For each assessment after the three separate spray events, plots treated with the carbamate had 48, 147 and 28%, those treated with pyrethroid 53, 210 and 89%, those treated with carbamate/pyrethroid 28, 108 and 64% and those treated with neonicotinoid 43, 55 and 11% of the numbers of M. persicae by comparison with untreated controls. Only the proportions of surviving aphids from the genotype containing no insecticide resistance traits and the genotype containing elevated carboxylesterases matched ratios predicted from the selective advantage afforded by the resistance traits alone. Survival of aphids from the other three genotypes that carried 1–3 of the insecticide resistance traits differed from expectations in all cases, possibly owing to physiological differences, including their vulnerability to predators and hymenopterous parasitoids present at the site and/or their carrying unknown insecticide resistance mechanisms. CONCLUSION: Control strategies based on knowledge of the genetically determined insecticide resistance profile of an M. persicae population alone are insufficient. Hence, other important factors contributing to aphid survival under insecticide pressure need to be considered. Copyright © 2012 Society of Chemical Industry     

蔬菜蚜虫抗药性现状及抗性治理策略

蚜虫是为害蔬菜作物的一类重要害虫,如不防治会给蔬菜生产造成重大经济损失。长期以来主要依靠使用农药防治蔬菜蚜虫,但由于化学农药的不合理使用,蔬菜蚜虫对有机磷、拟除虫菊酯、氨基甲酸酯、新烟碱等多种类型的杀虫药剂均产生了不同程度的抗性。本文对常见的蔬菜蚜虫的抗药性现状、抗药性机理以及治理策略进行了论述,以期为该类害虫的可持续控制提供参考。     

棉蚜抗药性及其化学防治

棉蚜［Aphis gossypii（Glover）］属半翅目蚜科,是一种世界性的害虫,主要通过取食植物汁液和传播病毒给农业生产造成严重损失。长期以来,棉蚜的防治一直以化学防治为主,棉蚜对有机氯、有机磷、氨基甲酸酯、拟除虫菊酯、新烟碱类等多种杀虫药剂已经产生了抗性。本文主要从棉蚜抗药性发展历史、抗药性机制以及棉蚜的化学防治等方面进行论述,期望能为农业生产上延缓棉蚜抗药性产生、有效治理棉蚜提供指导。     

The genus <Emphasis Type="Italic">Luteovirus</Emphasis> from infection to disease

Luteoviruses are economically important plant viruses. Specifically, barley yellow dwarf virus is epiphytotic to almost all small-grain cereal growing areas. The disease cycle is complex. This luteovirus has evolved several intelligent mechanisms to communicate with both plant and phloem-feeding insect-vector aphid. Environmental cues influence disease severity, aphid infestation and viral load. Within an aphid, virus circulates persistently in a non-propagative manner and is transmitted selectively to the host plants. Selection of viruses within aphids has a role in virus isolate prevalence over a specific area. In the host-plant system, the virus has to release its single sense-strand RNA genome (approx. 5.6 to 6 kb), translate and subsequently replicate its genome using its own replicase and host machinery. This review summarizes our current understanding of disease epidemiology and reviews the current literature encompassing viral infectivity, economic impact and control measures.     

PP 1/70 (4) Aphid vectors of Barley yellow dwarf virus

Specific scope

This Standard describes the conduct of trials for the efficacy evaluation of insecticides against aphid vectors of Barley yellow dwarf virus.

Specific approval and amendment

First approved in 1983‐09. Aligned with revised standard text in 1997. Revision approved in 2005‐09 and 2017‐09.     

Virus Transmission Phenotype Is Correlated with Host Adaptation Among Genetically Diverse Populations of the Aphid Schizaphis graminum

ABSTRACT Schizaphis graminum is an important insect pest of several grain crops and an efficient vector of cereal-infecting luteoviruses and poleroviruses. We examined the virus transmission characteristics of several distinct populations and various developmental stages of the aphid. Seven well-characterized S. graminum biotypes maintained at the USDA-ARS laboratory in Stillwater, OK, and two biotypes maintained in New York (one collected in Wisconsin and the other collected in South Carolina) were tested for their ability to transmit five viruses that cause barley yellow dwarf disease (BYD). Four of the Oklahoma biotypes, which do not commonly colonize agronomic crops, and the Wisconsin biotype, were efficient vectors of several viruses. The three other Oklahoma biotypes, which do colonize agronomic crops, and the South Carolina biotype, were poor vectors of all five viruses. Thus, the vector specificity long associated with viruses causing BYD is not limited to the level of aphid species; it clearly extends to populations within a single species. S. graminum nymphs are reported to be more efficient vectors of Barley yellow dwarf virus (BYDV-SGV) than are adults. This was confirmed only for the Wisconsin biotype, but not for the other eight S. graminum biotypes. Thus, there does not appear to be a generalized developmentally regulated barrier to the transmission of BYDV-SGV in S. graminum. Furthermore, the developmentally regulated vector competency observed in the Wisconsin biotype did not extend to other viruses. BYDV-PAV and Cereal yellow dwarf virus-RPV were transmitted with similar efficiency by all S. graminum biotypes when acquired by nymphs or adults.     

Biological characterization of sulfoxaflor, a novel insecticide

BACKGROUND: The commercialization of new insecticides is important for ensuring that multiple effective product choices are available. In particular, new insecticides that exhibit high potency and lack insecticidal cross‐resistance are particularly useful in insecticide resistance management (IRM) programs. Sulfoxaflor possesses these characteristics and is the first compound under development from the novel sulfoxamine class of insecticides. RESULTS: In the laboratory, sulfoxaflor demonstrated high levels of insecticidal potency against a broad range of sap‐feeding insect species. The potency of sulfoxaflor was comparable with that of commercial products, including neonicotinoids, for the control of a wide range of aphids, whiteflies (Homoptera) and true bugs (Heteroptera). Sulfoxaflor performed equally well in the laboratory against both insecticide‐susceptible and insecticide‐resistant populations of sweetpotato whitefly, Bemisia tabaci Gennadius, and brown planthopper, Nilaparvata lugens (Stål), including populations resistant to the neonicotinoid insecticide imidacloprid. These laboratory efficacy trends were confirmed in field trials from multiple geographies and crops, and in populations of insects with histories of repeated exposure to insecticides. In particular, a sulfoxaflor use rate of 25 g ha^?1 against cotton aphid (Aphis gossypii Glover) outperformed acetamiprid (25 g ha^?1) and dicrotophos (560 g ha^?1). Sulfoxaflor (50 g ha^?1) provided a control of sweetpotato whitefly equivalent to that of acetamiprid (75 g ha^?1) and imidacloprid (50 g ha^?1) and better than that of thiamethoxam (50 g ha^?1). CONCLUSION: The novel chemistry of sulfoxaflor, its unique biological spectrum of activity and its lack of cross‐resistance highlight the potential of sulfoxaflor as an important new tool for the control of sap‐feeding insect pests. Copyright © 2010 Society of Chemical Industry     

Genetic Regulation of Polerovirus and Luteovirus Transmission in the Aphid Schizaphis graminum

ABSTRACT Sexual forms of two genotypes of the aphid Schizaphis graminum, one a vector, the other a nonvector of two viruses that cause barley yellow dwarf disease (Barley yellow dwarf virus [BYDV]-SGV, luteovirus and Cereal yellow dwarf virus-RPV, polerovirus), were mated to generate F1 and F2 populations. Segregation of the transmission phenotype for both viruses in the F1 and F2 populations indicated that the transmission phenotype is under genetic control and that the parents are heterozygous for genes involved in transmission. The ability to transmit both viruses was correlated within the F1 and F2 populations, suggesting that a major gene or linked genes regulate the transmission. However, individual hybrid genotypes differed significantly in their ability to transmit each virus, indicating that in addition to a major gene, minor genes can affect the transmission of each virus independently. Gut and salivary gland associated transmission barriers were identified in the nonvector parent and some progeny, while other progeny possessed only a gut barrier or a salivary gland barrier. Hemolymph factors do not appear to be involved in determining the transmission phenotype. These results provide direct evidence that aphid transmission of luteoviruses is genetically regulated in the insect and that the tissue-specific barriers to virus transmission are not genetically linked.     

麦蚜对拟除虫菊酯类杀虫剂抗性研究进展

麦蚜是为害小麦的一类重要害虫,广泛分布于我国各小麦种植区。2016年-2018年我国麦蚜总体偏重发生,严重影响小麦产量和品质,造成巨大的经济损失。拟除虫菊酯类杀虫剂是防治麦蚜的主要杀虫剂类型之一,但由于化学农药的长期使用,麦蚜对拟除虫菊酯类杀虫剂产生了不同程度的抗性。本文综述了拟除虫菊酯类杀虫剂作用机制、麦蚜对拟除虫菊酯类杀虫剂的抗性现状以及近年来拟除虫菊酯类杀虫剂抗性机制研究的主要进展。     

新烟碱类杀虫剂选择作用的分子机理

新烟碱类是一类重要的新颖杀虫剂,其发现是近20年来杀虫剂研究的一个里程碑。烟碱类和新烟碱类杀虫剂虽然都是作为后突触烟碱乙酰胆碱受体(nAChRs)的激动剂作用于昆虫的神经系统,但由于作用方式不同,新烟碱类杀虫剂对昆虫表现出选择性毒性。根据烟碱类和新烟碱类杀虫剂结构与活性的关系、分子特性以及它们与nAChR的结合部位和亚部位的选择性阐释了新烟碱类杀虫剂选择作用的分子机理。     

Neonicotinoids-from zero to hero in insecticide chemistry

In recent years, neonicotinoids have been the fastest-growing class of insecticides in modern crop protection, with widespread use against a broad spectrum of sucking and certain chewing pests. As potent agonists, they act selectively on insect nicotinic acetylcholine receptors, their molecular target site. The discovery of neonicotinoids can be considered as a milestone in insecticide research and facilitates greatly the understanding of the functional properties of insect nicotinic acetylcholine receptors. Because of the relatively low risk for non-target organisms and environment, the high target specificity of neonicotinoid insecticides and their versatility in application methods, this important class has to be maintained globally for integrated pest management strategies and insect resistance management programmes. This review comprehensively describes particularly the origin, structure and bonding as well as associated properties of neonicotinoid insecticides.     

Pyrethroid resistance and thiacloprid baseline susceptibility of European populations of Meligethes aeneus (Coleoptera: Nitidulidae) collected in winter oilseed rape

BACKGROUND: Pollen beetle, Meligethes aeneus F. (Coleoptera: Nitidulidae), is a major pest in European winter oilseed rape. Recently, control failures with pyrethroid insecticides commonly used to control this pest have been reported in many European countries. For resistance management purposes, the neonicotinoid insecticide thiacloprid was widely introduced as a new mode of action for pollen beetle control. RESULTS: A number of pollen beetle populations collected in Germany, France, Austria, Great Britain, Sweden, Denmark, Finland, Poland, Czech Republic and Ukraine were tested for pyrethroid resistance using lambda‐cyhalothrin‐coated glass vials (adult vial test). Most of the populations tested exhibited substantial levels of resistance to lambda‐cyhalothrin, and resistance ratios ranged from < 10 to > 2000. A similar resistance monitoring bioassay for the neonicotinoid insecticide thiacloprid was developed and validated by assessing baseline susceptibility data for 88 European pollen beetle populations. A variation of less than fivefold in response to thiacloprid was detected. The thiacloprid adult vial bioassay is based on glass vials coated with an oil‐dispersion‐based formulation of thiacloprid, resulting in a much better bioavailability compared with technical material. Analytical measurements revealed a > 56 and 28 day stability of thiacloprid and lambda‐cyhalothrin in coated glass vials at room temperature, respectively. No cross‐resistance between thiacloprid and lambda‐cyhalothrin based on log‐dose probit–mortality data was detected. CONCLUSION: Pyrethroid resistance in many European populations of M. aeneus was confirmed, whereas all populations are susceptible to thiacloprid when tested in a newly designed and validated monitoring bioassay based on glass vials coated with oil‐dispersion‐formulated thiacloprid. Based on the homogeneous results, it is concluded that thiacloprid could be an important chemical tool for pollen beetle resistance management strategies in European winter oilseed rape. Copyright © 2011 Society of Chemical Industry     

Variation in Transmission Efficiency Among Barley yellow dwarf virus-RMV Isolates and Clones of the Normally Inefficient Aphid Vector, Rhopalosiphum padi

The RMV strain of Barley yellow dwarf virus (BYDV-RMV) is an unassigned member of the Luteoviridae that causes barley yellow dwarf in various cereal crops. The virus is most efficiently vectored by the aphid Rhopalosiphum maidis, but can also be vectored with varying efficiency by R. padi and Schizaphis graminum. Field collections of alate aphids migrating into the emerging winter wheat crop in the fall of 1994 in central New York identified a high proportion of R. padi transmitting BYDV-RMV. This prompted a comparison of the BYDV-RMV isolates and the R. padi populations found in the field with type virus and aphid species maintained in the laboratory. A majority of the field isolates of BYDV-RMV were similar to each other and to the type BYDV-RMV isolate in disease severity on oat and in transmission by the laboratory-maintained population of R. maidis and a field-collected population of R. maidis. However, several field populations of R. padi differed in their ability to transmit the various BYDV-RMV isolates. The transmission efficiency of the R. padi clones was increased if acquisition and inoculation feeding periods were allowed at higher temperatures. In addition, the transmission efficiency of BYDV-RMV was significantly influenced by the aphid that inoculated the virus source tissue. In general, BYDV-RMV transmission by R. padi was higher when R. padi was the aphid that inoculated the source tissue than when R. maidis was the inoculating aphid. The magnitude of the change varied among virus isolates and R. padi clones. These results indicate that, under certain environmental conditions, R. padi can play a significant role in the epidemiology of BYDV-RMV. This may be especially significant in regions where corn is a major source of virus and of aphids that can carry virus into a fall-planted wheat crop.     

Soil application of neonicotinoid insecticides for control of insect pests in wine grape vineyards

BACKGROUND: Soil application of systemic neonicotinoid insecticides can provide opportunities for long‐term control of insect pests in vineyards, with minimal risk of pesticide drift or worker exposure. This study compared the effectiveness of neonicotinoid insecticides applied via irrigation injection on key early‐season and mid‐season insect pests of vineyards in the eastern United States. RESULTS: On vines trained to grow on drip irrigation, early‐season application of imidacloprid, clothianidin, thiamethoxam and dinotefuran provided high levels of control against the potato leafhopper, Empoasca fabae. Protection of vines against Japanese beetle, Popillia japonica, and grape berry moth, Paralobesia viteana, was also observed after mid‐season applications. Efficacy was poor in commercial vineyards when treatments were applied to the soil before irrigation or rain, indicating that vines must be grown with an irrigation system for efficient uptake of the insecticide. CONCLUSIONS: In drip‐irrigated vineyards, soil‐applied neonicotinoids can be used to provide long residual control of either early‐season or mid‐ to late‐season foliage pests of vineyards. This approach can reduce the dependence on foliar‐applied insecticides, with associated benefits for non‐target exposure to workers and natural enemies. Copyright © 2012 Society of Chemical Industry     

Effect of distribution and concentration of topically applied neonicotinoid insecticides in buffalograss,Buchloe dactyloides,leaf tissues on the differential mortality of Blissus occiduus under field conditions

BACKGROUND: Neonicotinoid insecticides are generally efficacious against many turfgrass pests, including several important phloem‐feeding insects. However, inconsistencies in control of western chinch bugs, Blissus occiduus, have been documented in field efficacy studies. This research investigated the efficacy of three neonicotinoid insecticides (clothianidin, imidacloprid and thiamethoxam) against B. occiduus in buffalograss under field conditions and detected statistically significant differences in B. occiduus numbers among treatments. A subsequent study documented the relative quantity and degradation rate of these insecticides in buffalograss systemic leaf tissues, using HPLC. RESULTS: Neonicotinoid insecticides initially provided significant reductions in B. occiduus numbers, but mortality diminished over the course of the field studies. Furthermore, while all three neonicotinoids were present in the assayed buffalograss leaf tissues, imidacloprid concentrations were significantly higher than those of clothianidin and thiamethoxam. Over the course of the 28 day study, thiamethoxam concentrations declined 700‐fold, whereas imidacloprid and clothianidin declined only 70‐fold and 60‐fold respectively. CONCLUSIONS: Field studies continued to verify inconsistencies in B. occiduus control with neonicotinoid insecticides. This is the first study to document the relative concentrations of topically applied neonicotinoid insecticides in buffalograss systemic leaf tissues. Copyright © 2012 Society of Chemical Industry     

Transmission of barley yellow dwarf virus by cereal aphids collected from different habitats on cereal farms

Cereal aphids were collected from cereal crops, from Poa annua within cereal fields, from Lolium perenne pastures and from wild grasses in hedge bottoms and around farm buildings. The frequency of barley yellow dwarf virus (BYDV) transmission was assessed by aphid transmission tests. There were differences in transmission rates between aphid species, between host species and between years. The transmission rates of Rhopalosiphum padi from the different host species were broadly similar whereas for Sitobion avenae, P. annua within cereal fields was significantly better than the other host species. Wild grasses other than P. annua were relatively poor sources of virus. A large percentage of aphids frequently transmitted more than one strain, suggesting that host plants are often infected with more than one BYDV strain.     

Report of resistance to the neonicotinoid insecticide imidacloprid in Trialeurodes vaporariorum (Hemiptera: Aleyrodidae)

Susceptibilities of UK and mainland European samples of Trialeurodes vaporariorum (Westwood) to the neonicotinoid insecticide imidacloprid were investigated over a 7 year period. All 24 strains collected between 1997 and 2003 showed similar baseline levels of susceptibility to that of a known susceptible laboratory strain when exposed to a diagnostic concentration (128 mg L(-1)) of formulated imidacloprid. Two samples collected during 2004, one from the UK and one from The Netherlands, demonstrated reduced susceptibility at this concentration. Using dose-response assays, the presence of resistant individuals was disclosed in both these strains; some individuals were unaffected at doses high enough to induce phytotoxic effects. This report represents the first confirmed cases of neonicotinoid resistance inducing control failures in T. vaporariorum, and highlights a need for careful vigilance to sustain the effectiveness of imidacloprid and related neonicotinoid insecticides.