Efficacy of pymetrozine against Myzus persicae and in reducing potato virus Y transmission on tobacco plants

Forty‐four parthenogenetic lineages of Myzus persicae s.l. (Sulzer) from tobacco crops and peach orchards located in various regions of Greece were examined to determine their response to the insecticide pymetrozine using leaf‐dip bio‐assays. The results show that the aphid has not developed resistance, as all lineages exhibited resistance factors bellow 6.0. In transmission experiments of potato virus Y (PVY) using a lineage of the tobacco‐adapted subspecies M. persicae nicotianae Blackman on tobacco plants, one foliar application with pymetrozine provided adequate protection for 7 days. Pymetrozine significantly reduced both virus acquisition and inoculation compared with the untreated control and the reduction was comparable to a mineral oil application. These results are discussed in terms of the advantage of incorporating pymetrozine as a compound of pest management strategies against M. persicae s.l. and for control of non‐persistent viruses, especially in crops such as tobacco because of the high selection pressure from neonicotinoids resulting in potential of resistance developing in aphid populations.     

Stylet penetration behavior of Myzus persicae related to transmission of Zucchini yellow mosaic virus

The direct current electrical penetration graph (DC‐EPG) technique was used to identify stylet penetration behaviors of Myzus persicae (Sulzer) (Hemiptera: Sternorrhyncha: Aphididae) that are related to successful acquisition and inoculation of the non‐persistently transmitted potyvirus, Zucchini yellow mosaic virus (ZYMV), to melon, Cucurbita pepo L. (Cucurbitaceae). Stylet penetration behaviors of two sources of M. persicae that differ in their ZYMV transmission efficiency were examined to determine if behavioral differences were related to their differing ZYMV transmission efficiencies. Successful acquisition of ZYMV by M. persicae was significantly related to longer total time in intracellular subphase II‐3 of potential drops. Successful inoculation of ZYMV by M. persicae was related to a greater number of intracellular punctures, shorter durations of intracellular punctures, and longer total time in intracellular subphase II‐1. Of these variables that were related to ZYMV transmission, the two aphid sources differed in the total time spent in subphases II‐1 and II‐3. These results suggest that the differences in ZYMV transmission efficiencies between the aphids may be at least partially caused by behavioral differences during stylet penetrations of the host plant tissue, specifically behaviors that occur during intracellular punctures.     

Feeding behavior of Myzus persicae on asparagus species susceptible and resistant to Asparagus virus 1

Asparagus virus 1 (AV‐1) infects Asparagus officinalis L. (Asparagaceae) in the field worldwide. However, various wild relatives of A. officinalis are resistant to AV‐1. Here we study the behavior of the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), on 19 AV‐1‐resistant wild relatives of A. officinalis. We focus on behavior that is associated with regular cell penetration, relevant for inoculation of AV‐1, and sieve element penetration to check for vector resistance and its potential influence on AV‐1 transmission. Parameters, relevant for the transmission of non‐persistent viruses and host plant acceptance, were obtained by the electrical penetration graph technique. Furthermore, phylloclade architecture of A. officinalis and its wild relatives was examined to study its influence on aphid behavior. Behavior of M. persicae displays many cell penetrations and long ingestion periods on A. officinalis, compared to the generally shorter cell penetrations (reduced potential for virus transmission) and reduced or no ingestion (phloem‐located aphid resistance) on wild relatives. Because effects on aphid behavior are not consistent throughout the group of the tested wild relatives of A. officinalis, with some wild relatives being susceptible to M. persicae, a common genetic background for AV‐1 and aphid resistance appears to be unlikely. However, the reduced potential of virus transmission as well as aphid resistance shown by some wild relatives may be useful for future breeding programs.     

园艺矿物油乳剂对亚洲柑橘木虱成虫刺吸行为的影响

目的】亚洲柑橘木虱Diaphorina citri是传播柑橘最重要病害黄龙病(huanglongbing, Candidatus Liberibacter asiaticus)的媒介昆虫,树冠喷施园艺矿物油(horticultural mineral oil, HMO)可以减少其在柑橘上的取食和产卵。本研究旨在探索植物组织内残留的园艺矿物油如何影响亚洲柑橘木虱成虫的取食行为。【方法】采用直流型刺吸电位仪(DC-EPG Giga-8)记录亚洲柑橘木虱成虫12 h内在喷施不同浓度(0.25%, 0.5%, 1%和2%, v/v)HMO(nC24)乳剂和清水(对照)时柑橘嫩叶上的刺探和取食行为并转换为波形信号,分析比较各处理的波形参数。【结果】不同浓度HMO乳剂处理显著提高了亚洲柑橘木虱成虫在柑橘叶片上的C波(路径波)持续时间百分比,显著减少了E2波(韧皮部吸食汁液)持续时间百分比,而对D(口针第一次接触韧皮部组织), E1(韧皮部出现唾液分泌) 和G(木质部吸食汁液) 波持续时间百分比没有显著影响。HMO处理组C波的每成虫波形累积时间(WDI)显著长于对照组,而各浓度处理之间没有显著差异,但D波WDI明显短于对照组。随着HMO浓度的增加, E1, E2和G波WDI显著下降,2% HMO处理组E1, E2和G波WDI明显低于其他浓度处理组。HMO乳剂处理明显减少了刺探次数;在HMO处理中,每成虫刺探次数和每成虫各波形次数均显著少于对照组,其中以1%和2% HMO乳剂处理最少。HMO乳剂处理组np波 (非刺探波)、D波、E2波的每成虫单次波形持续时间(WDE)均短于对照组,其中2% HMO乳剂处理后,D, E1和E2波WDE显著短于其他浓度处理和对照。同时,2% HMO乳剂处理推迟了从口器接触叶片到第1次开始刺探的时间和从口器接触叶片到第1次刺探到韧皮部的时间。【结论】结果表明,2% HMO乳剂显著减少亚洲柑橘木虱成虫在柑橘叶片上的取食次数和有效取食时间,同时还缩短了其在韧皮部分泌唾液和吸食汁液时间,因此可推荐矿物油用于柑橘黄龙病和亚洲柑橘木虱的综合防治体系。同时初步推断矿物油的作用机制可能是其进入植物气孔阻止植物挥发性物质的释放,抑制或掩盖柑橘叶片表面的挥发性物质从而减少了亚洲柑橘木虱在寄主上取食。     

Dynamics of Myzus persicae arrestment by volatiles from Potato leafroll virus‐infected potato plants during disease progression

Green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), an important pest of potato (Solanum tuberosum L.) (Solanaceae), preferentially settles on Potato leafroll virus (PLRV)‐infected potato plants as compared with non‐infected ones, primarily in response to volatile organic compounds (VOCs) released by the plants. In this study, we examined the dynamics of these effects, measuring arrestment of apterous M. persicae in response to VOC from upper, middle, and lower leaflets of PLRV‐infected potato plants at the same stage in disease progression (4 weeks after inoculation), but inoculated at 1, 3, or 5 weeks after transplanting (WAT). Sham‐inoculated plants were used as controls and VOC were collected and quantified. Aphid arrestment was greater on PLRV‐infected plants inoculated at 1 and 3 WAT as compared with sham‐inoculated plants, but this preference was reversed in plants inoculated at 5 WAT. Relative arrestment of M. persicae by infected plants and VOC release was greater for lower and middle leaflets than for upper leaflets at 1 and 3 WAT compared to sham‐inoculated plants. The reverse was observed in plants inoculated at 5 WAT. Findings indicate that aphid preference is influenced by VOC release from PLRV‐ or sham‐inoculated potato plants and that VOC emissions and aphid preference depend upon the age at inoculation and leaf position within the potato plants. The implications of these dynamics in vector behavior for spread of PLRV in the field in natural and managed systems are discussed.     

The effect of mineral oil on stylet activities and potato virus Y transmission by aphids

Mineral oil sprayed onto potato virus Y (PVY) infected tobacco plants reduced acquisition of this potyvirus by Myzus persicae (Sulz.). Although the pre-penetration activities of aphids were longer on oil treated leaves, the inhibitory effect of the oil could not be attributed to differences in the duration of stylet penetration. Aphids were therefore made part of a DC circuit in order to investigate their stylet activities during penetration of PVY infected source plants and healthy test plants. Both acquisition and inoculation of the virus were reduced by the presence of oil on the plant surface, but these reductions could not be related to electrically recorded differences in plant penetration behaviour. In particular, stylet punctures of plant cell membranes were not reduced by mineral oil. Non-behavioural reasons are suggested to explain the mode of action of the oil.     

The NIa‐Pro protein of Turnip mosaic virus improves growth and reproduction of the aphid vector,Myzus persicae (green peach aphid)

Many plant viruses depend on aphids and other phloem‐feeding insects for transmission within and among host plants. Thus, viruses may promote their own transmission by manipulating plant physiology to attract aphids and increase aphid reproduction. Consistent with this hypothesis, Myzus persicae (green peach aphids) prefer to settle on Nicotiana benthamiana infected with Turnip mosaic virus (TuMV) and fecundity on virus‐infected N. benthamiana and Arabidopsis thaliana (Arabidopsis) is higher than on uninfected controls. TuMV infection suppresses callose deposition, an important plant defense, and increases the amount of free amino acids, the major source of nitrogen for aphids. To investigate the underlying molecular mechanisms of this phenomenon, 10 TuMV genes were over‐expressed in plants to determine their effects on aphid reproduction. Production of a single TuMV protein, nuclear inclusion a‐protease domain (NIa‐Pro), increased M. persicae reproduction on both N. benthamiana and Arabidopsis. Similar to the effects that are observed during TuMV infection, NIa‐Pro expression alone increased aphid arrestment, suppressed callose deposition and increased the abundance of free amino acids. Together, these results suggest a function for the TuMV NIa‐Pro protein in manipulating the physiology of host plants. By attracting aphid vectors and promoting their reproduction, TuMV may influence plant–aphid interactions to promote its own transmission.     

Barley yellow dwarf virus transmission and feeding behaviour of Rhopalosiphum padi on Hordeum bulbosum clones

A Hordeum bulbosum L. (Poaceae) clone A17 was identified, which showed complete resistance to Barley yellow dwarf virus (BYDV) and Cereal yellow dwarf virus (CYDV). It was not possible to infect plants of A17 with BYDV‐PAV, ‐MAV, or with CYDV‐RPV by the aphid vectors Rhopalosiphum padi (L.) or Sitobion avenae (Fabricius) (both Hemiptera: Aphididae). Plants of the A17 clone and of the BYDV‐susceptible H. bulbosum clone A21 revealed some resistance to R. padi compared to the susceptible winter barley cultivar Rubina [Hordeum vulgare L. (Poaceae)]. The development time to the imago was longer and the number of nymphs was reduced on both clones compared with cv. Rubina. The probing and feeding behaviour of R. padi on plants of the H. bulbosum clones was studied over 12 h and compared with that on plants of the barley cv. Rubina. Principal component analysis of the results of the feeding behaviour revealed a clear separation of the H. bulbosum genotypes from Rubina. On H. bulbosum the number of penetrations was higher but total feeding time was shorter. Significant differences were mainly found in the phloem feeding parameters for plants of both clones in comparison to Rubina, with the virus resistant A17 clone having the strongest effect and the susceptible A21 clone being intermediate. Most significant differences were found in parameters of the phloem salivation phase. On A17, an average of less than one (0.9) E1 phase per plant was observed (3.3 on A21 and 5.7 on Rubina) and its duration was reduced to less than 1 min (0.9 min) in comparison to 2.4 min on A21 and 5.7 min on Rubina. Also, the phloem feeding (E2) phase was clearly reduced on A17 plants with 0.5 E2 phases per test and a mean duration of 1.1 min in contrast with 2.9 and 3.5 E2 phases per test and 34.1 and 421.3 min for A21 and Rubina, respectively. These results point towards a phloem‐localized factor for aphid resistance in H. bulbosum, i.e., on A17 plants the phloem salivation time is too short for a successful infection by BYDV leading to vector resistance.     

矿物油处理对马铃薯长管蚜定向和取食行为的影响（英文）

大田和实验室研究均表明矿物油的施用可有效降低蚜虫对非持久性病毒的传播。我们分别于矿物油喷施马铃薯植株24 h和7 d后,调查其对马铃薯长管蚜Macrosiphum euphorbiae行为的影响;采用暗室生测法调查了蚜虫对处理的植物挥发性化合物的反应;采用刺探电位技术（EPG）评价了矿物油处理对蚜虫取食行为的影响。结果表明：矿物油处理导致植物对寄主的引诱作用失效,这种效果至少持续24 h。矿物油处理马铃薯植株24 h和7 d后,蚜虫对处理植株的取食行为发生改变。开始记录至第1次刺探所需时间降低,但只在处理7 d后显著降低,提示矿物油处理有助于蚜虫口针的穿刺。然而,流涎阶段以及韧皮部汁液吸食阶段（摄食阶段）显著缩短。本研究中观察到的蚜虫行为的改变不能充分解释施用矿物油的大田中为什么出现7 d 的保护作用,因此可能还存在其他的机制。     

Comparison of transmission efficiency of various isolates of Potato virus Y among three aphid vectors

Potato virus Y (PVY) strains are transmitted by different aphid species in a non‐persistent, non‐circulative manner. Green peach aphid (GPA), Myzus persicae Sulzer, is the most efficient vector in laboratory studies, but potato aphid (PA), Macrosiphum euphorbiae Thomas (both Hemiptera: Aphididae, Macrosiphini), and bird cherry‐oat aphid (BCOA), Rhopalosiphum padi L. (Hemiptera: Aphididae, Aphidini), also contribute to PVY transmission. Studies were conducted with GPA, PA, and BCOA to assess PVY transmission efficiency for various isolates of the same strain. Treatments included three PVY strains (PVY^O, PVY^N:O, PVY^NTN) and two isolates of each strain (Oz and NY090031 for PVY^O; Alt and NY090004 for PVY^N:O; N4 and NY090029 for PVY^NTN), using each of three aphid species as well as a sham inoculation. Virus‐free tissue‐cultured plantlets of potato cv. Russet Burbank were used as virus source and recipient plants. Five weeks post inoculation, recipient plants were tested with quantitative DAS‐ELISA to assess infection percentage and virus titer. ELISA‐positive recipient plants were assayed with RT‐PCR to confirm presence of the expected strains. Transmission efficiency (percentage infection of plants) was highest for GPA, intermediate for BCOA, and lowest for PA. For all aphid species, transmission efficiency did not differ significantly between isolates within each strain. No correlations were found among source plant titer, infection percentage, and recipient plant titer. For both GPA and BCOA, isolates of PVY^NTN were transmitted with greatest efficiency followed by isolates of PVY^O and PVY^N:O, which might help explain the increasing prevalence of necrotic strains in potato‐growing regions. Bird cherry‐oat aphid transmitted PVY with higher efficiency than previously reported, suggesting that this species is more important to PVY epidemiology than has been considered.     

Modification of Macrosiphum euphorbiae colonisation behaviour and reproduction on potato plants treated by mineral oil

Although mineral oil spray is one of the most effective ways to control the transmission of non‐persistent aphid‐borne viruses in the field, its mode of action is poorly understood. In this study, the effects of mineral oil treatment of potato plants on host selection behaviour, growth, and reproduction of potato aphids, Macrosiphum euphorbiae (Thomas) (Hemiptera: Aphididae), were investigated. The effects were assessed 30 min, 1 day, and 7 days after treatment, (1) on aphid orientation behaviour by using a Y‐tube olfactometer, and (2) on aphid feeding behaviour by using the electrical penetration graph (EPG) technique. Olfactory experiments showed that the oil had a repulsive effect only 30 min after spraying. EPG experiments showed a slight modification of the aphid feeding behaviour mainly 7 days after treatment. The number of both salivation and sap ingestion events during the phloem phases were increased 7 days after treatment. In addition, irrespective of the time after treatment, xylem ingestion time was increased. Clip cage experiments were set up to assess potential effects of the oil treatment on aphid survival and population parameters. Nymphal mortality was increased on treated plants, whereas fecundity of surviving insects was enhanced. The antagonistic effects of oil treatment on aphids are discussed in a plant protection context.     

Effect of mineral oil on Potato virus Y acquisition by Rhopalosiphum padi

Seed potato crops are currently sprayed weekly with mineral oil to prevent transmission of the Potato virus Y (PVY; Potyviridae: Potyvirus), one of the most prevalent and important non‐persistent viruses affecting potato production. In spite of its wide usage as inhibitor of virus transmission, the mode of action for mineral oil is poorly known. The objective of this study was to quantify the effect of dosage and time from application of mineral oil on the inhibition of PVY acquisition. The bird cherry‐oat aphid, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), known as vector of PVY, was used in all the experiments. The results indicated that mineral oil efficiently decreased PVY acquisition by 75 and 70% 1 day after application of 5 and 10 l ha^?1, respectively. The inhibition effect decreased with time from application; mineral oil inhibits acquisition for less than 4 days at 5 l ha^?1 and between 8 and 12 days at 10 l ha^?1. As mineral oil was detected in the body of fewer aphids when they fed on plants 1 day after oil application, a change in the aphid probing behaviour on mineral oil‐treated plants was deduced. These results support the hypothesis that mineral oil physically inhibits the binding of the virus at the tip of the stylets.     

Effect of mineral oils on host plant selection and probing behavior of Rhopalosiphum padi

Aphids that colonize and reproduce on potato are some of the most efficient vectors of Potato virus Y (PVY) (Potyviridae: Potyvirus), and hence these aphids have been the focus of the majority of studies to date. However, other non‐colonizing aphids can also function as vectors. Mineral oil is the only product available to growers that effectively prevents the spread of PVY in potato seed production. Most previous studies focused on the effect of mineral oil on the behavior of aphids on their preferential host plant, and consequently there is a lack of information for non‐colonizing aphids on potato plants. The objective of this study was to determine the effect of spraying potatoes with one of two mineral oils, Superior 70 or Vazyl‐Y, on host selection and probing behavior of the non‐colonizing aphid Rhopalosiphum padi (L.) (Hemiptera: Aphididae). The electrical penetration graph (EPG) technique, combined with ethological observations, determined that there was no difference in R. padi behavior on potato plants treated with Superior 70. However, there were few significant changes in R. padi behavior on plants sprayed with Vazyl‐Y, including a delay in the initiation of stylet penetration and an increase in the duration of xylem sap ingestion. These new data support previous results and confirm that the mode of action of mineral oil in the reduction of the spread of PVY is not solely due to the modification of the behavior of aphids.     

Characteristics of sugarcane white leaf phytoplasma transmission by the leafhopper Matsumuratettix hiroglyphicus

The leafhopper Matsumuratettix hiroglyphicus (Matsumura) (Hemiptera: Cicadellidae) is the most important vector of sugarcane white leaf (SCWL) phytoplasma that significantly affects the sugarcane crop in Asia. Here, we aimed to study the characteristics of SCWL phytoplasma transmission by M. hiroglyphicus. To this end, the stylet penetration activities performed during the acquisition access period (AAP) and inoculation access period (IAP) were investigated by the direct current electrical penetration graph technique and confirmed by quantitative polymerase chain reaction (qPCR). Additionally, the latent period (LP) of SCWL phytoplasma in the vector was determined by qPCR and localised by fluorescent in situ hybridisation. The results indicated that the acquisition of SCWL phytoplasma occurred during phloem ingestion (waveform D), whereas its inoculation was associated with salivation into the phloem sieve element (waveform C). The minimum AAP was 15 min and the minimum duration of phloem ingestion was 2.35 min. The minimum LP of SCWL phytoplasma in the vector was at least 14 days; then, SCWL phytoplasma moved to the salivary glands of the insect, enabling the transmission of the pathogen to the host plants. The minimum IAP for a successful transmission of SCWL phytoplasma to the host plants was 11–12 min, with a minimum duration of salivation into phloem of 1.35 min. The female vectors had higher SCWL phytoplasma copy numbers than the male vectors, and displayed faster AAP, IAP, and LP. Overall, our findings provide important information related to the feeding behaviour of M. hiroglyphicus and its effect on the transmission of SCWL phytoplasma.