Evaluation of some systemic granular insecticides againstMyzus persicae Sulzer on potatoes

Summary Field evaluation of seven granular insecticides againstMyzus persicae revealed that phorate, aldicarb and disulfoton (both Di-Syston and Solvirex) are effective in reducing and keeping down the population ofM. persicae when applied either at sowing or at first earthing up.     

Identification of the Population Structure of Myzus persicae (Hemiptera: Aphididae) on Peach Trees in China Using Microsatellites

In this study, we characterized the genetic structure of Myzus persicae (Sulzer) (Hemiptera: Aphididae) populations in China using microsatellites. We expected that these data will reveal the genetic relationships among various populations of M. persicae and will be of value in the development of better methods for pest control. Four hundred sixty individuals from 23 areas over 13 provinces were collected in the early spring of 2010, all from their primary host, Prunus persicae. The markers analyzed were highly polymorphic, as demonstrated by the expected heterozygosity value (H_e = 0.861) and the Polymorphism Information Content (PIC = 0.847), which indicated that M. persicae maintains a high level of genetic diversity. Analysis of molecular variance revealed an intermediate level of population differentiation among M. persicae populations (F_ST = 0.1215). Geographic isolation existed among these populations, and, consequently, the genetic structure of the populations was split into a southern group and a northern group divided by the Yangtse River.     

抗蚜高产辣椒品种鉴定评价

为了有效满足海南辣椒产业发展需求,系统开展了适于海南种植的抗蚜辣椒品种鉴定与评价.抗蚜性鉴定结果表明,32个参试辣椒品种中,'猪大肠'石柱朝天红'博辣15号'辣丰三号'和'小米椒'5个品种对桃蚜表现为抗蚜,'福康8号'翡翠甜椒'翠玉甜椒'薄冠008'皇帝椒'新香2号'和'干辣3号'7个品种对桃蚜表现为感蚜,'大羊角椒'...     

莰酮对蚜虫生物活性的研究

进行了樟树(CinnamomumcamphoraL.)中的莰酮(CamphorC10H160)对蚜虫的触杀、熏蒸毒力和拒食活性研究。结果表明,处理后24h莰酮对菜缢管蚜、桃蚜和棉蚜触杀作用的LD50分别为3.12×10-3,2.04×10-3,0.68×10-3 ng/头,熏蒸作用的LC50分别为3.44,2.56,1.06mg/L,拒食作用的AFC50分别为3.34,2.98,1.32mg/L。经回归和相关分析,处理浓度与作用效果相关性均达到极显著或显著水平。莰酮在田间防治菜缢管蚜的效果显著。     

Myzus persicae (Sulzer) in diffuse light and dark rustic storages and resultant PLRV transmission

Population levels ofMyzus persicae (Sulzer) were studied on potato tubers in diffuse light and dark rustic storage houses in Peru. No differences in numbers of aphids/sprouted eye on potatoes infested naturally during storage in diffuse light or darkness were observed. Significantly more alate aphids were observed on tubers stored in darkness than in diffuse light storage houses. Viral transmission was occurring during the storage period. The incidence of viral transmission was not significantly influenced by storing tubers in diffuse light or dark storages. There were significantly more plants infected with virus from tubers that had not been sprayed for aphid control than from tubers that had been sprayed     

烟蚜与烟草黄瓜花叶病田间消长动态研究

为建立烟草黄瓜花叶病（CMV）的预测预报系统,对烟蚜、烟草黄瓜花叶病的田间消长动态进行调查．调查结果表明：烟蚜在田间洧长规律呈单峰型,有翅蚜峰日早于无翅蚜峰日10天,僵蚜峰日落后无翅蚜峰日5天;烟草黄瓜花叶病的发生与有趣蚜的迁入消长紧密相关．     

Insecticide toxicity to three strains of green peach aphid (Myzus persicae Sulzer) reared on resistant and susceptible potato cultivars

Three green peach aphid (GPA) strains, Myzus persicae (Sulzer) (Homoptera: Aphididae) obtained from New York, Puerto Rico and Minnesota, were reared on resistant potato hybrid D888-4 and a susceptible cv. Red Pontiac. No significant differences in GPA mortality were observed when aphids were reared on either the resistant or susceptible potato cultivars and later exposed to methamidophos 4EC, pirimicarb 50 WP, azinphos-methyl 2EC or permethrin 2EC. The interaction between the four insecticides × three GPA strains was significant. Of the three aphid strains, those from Minnesota had the lowest susceptibility to permethrin, pirimicarb and azinophos-methyl. No mortality was observed in this GPA strain when tested with azinphosmethyl.     

Relative toxicity of insecticides to the crucifer pests Plutella xylostella and Myzus persicae and their natural enemies

The widespread and intensive use of conventional pesticides, particularly insecticides, presents a major risk to natural enemies of target pests, as well as to the environment in general. The aim of this study was to investigate the differential intrinsic toxicity of insecticides to two key pests of crucifers, Plutella xylostella and Myzus persicae and their respective hymenopteran parasitoids, Cotesia vestalis and Aphidius colemani. Such knowledge can help inform effective integration of insecticides and biological control in IPM systems. Three insecticides generally regarded as being compatible with natural enemies (abamectin, spinosad and indoxacarb) and one compound regarded as harmful to natural enemies (lambda-cyhalothrin) were examined. A comparative measure of the intrinsic toxicity of fresh deposits of insecticides on Chinese cabbage leaf discs was determined for both pest and parasitoids species after exposure to insecticide for 24 h and 120 h, and after 24 h exposure to insecticide plus 96 h on untreated leaf discs. Differences in the susceptibility of pests and parasitoids to different insecticides were marked for P. xylostella and C. vestalis, LC₅₀ values being significantly lower for the pest species. Such differences were not observed for M. persicae and A. colemani. There was a direct relationship between dose, exposure time and toxicity for all insecticides tested. All insecticides tested showed lower toxicity to both parasitoids compared with P. xylostella, which suggests that for this pest species side-effects on parasitoids can be minimised through IPM practices that reduce exposure time to such non-target organisms.     

Behavioral Responses of Green Peach Aphid, Myzus persicae (Sulzer), to the Volatile Organic Compound Emissions from Four Potato Varieties

Green peach aphid Myzus persicae (Sulzer) is a serious pest of potato and causes severe yield loss to potato production worldwide. The volatiles emitted from potato plants influence host selection by M. persicae. A laboratory experiment was conducted to study how these volatile emissions vary among four potato varieties (IdaRose, Desiree, Chipeta and Russet Burbank) having different genetic backgrounds, and to compare the aphid responses to the volatiles emitted by these varieties. Results indicated that headspace volatiles detected, and aphid responses, differed significantly among the varieties. Myzus persicae arrestment was greater in response to Desiree and Chipeta than on Russet Burbank and arrestment on IdaRose was intermediate and did not differ significantly from any of the other varieties, but the arrestment was not related to the total concentration of volatiles released by these varieties. This indicates that the blend of volatiles was important for eliciting arrestment. Eigenvector weightings of principal component 1 were predominantly sesquiterpenes (especially caryophyllene, sesquiphellandrene, α-farnesene and longifolene), whereas those for principal component 2 were predominantly aldehydes and green leaf volatiles (n-hexana1, (Z)-3-hexenol, (E)-2-hexenal and nonanal. The pedigrees of the varieties are not associated with the volatile blends or aphid responses.     

Regional susceptibilities to 12 insecticides of melon and cotton aphid,Aphis gossypii (Hemiptera: Aphididae) and a point mutation associated with imidacloprid resistance

The melon and cotton aphid Aphis gossypii Glover (Hemiptera; Aphididae) is one of the most serious pests worldwide. We surveyed insecticide susceptibility in A. gossypii field populations to 12 insecticides (6 neonicotinoids, 3 pyrethroids and 3 others) to examine resistance ratios. The levels of insecticide resistance were extremely high, especially to neonicotinoids, such as acetamiprid, clothianidin, thiacloprid and imidacloprid. To identify the neonicotinoid resistance mechanisms, we used an imidacloprid-resistant (IMI-R) strain as a model strain. IMI-R showed an extremely high resistance ratio and also cross-resistance to all the test neonicotinoids. However, there was little or no cross-resistance to the other insecticides, including sulfoxaflor. Synergist tests and enzyme activity assays suggested the absence of resistance mechanisms based on enhanced detoxification enzymes, such as cytochrome P450, esterase and glutathione S-transferase. One point mutation was found in the beta1 subunit loop D region of the nicotinic acetylcholine receptor (nAChR) of the IMI-R strain. This R81T point mutation was also found in field populations collected from 5 regions. Therefore, the R81T point mutation was identified as an important mechanism of imidacloprid resistance in A. gossypii.     

Monitoring for MACE resistance in the tobacco-adapted form of the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae) in the eastern United States

Organophosphate and carbamate insecticides exert their neurotoxic effects by inhibiting acetylcholinesterase (AChE), thereby, prolonging the action of acetylcholine at cholinergic synapses, resulting in neuronal hyperexcitation. Mutations at the AChE target site confer modified acetylcholinesterase (MACE) phenotypes. Target-site insensitivity of AChE was characterized in field-collected, tobacco-adapted forms of the green peach aphid, Myzus persicae (Sulzer), from nine different states in the eastern United States from 2004 to 2007. The specific activity of the AChE among the 65 aphid colonies screened by Ellman's assay ranged from 0.017–0.259 U/min/mg protein. Eight colonies, with a wide range of specific activities were chosen to study the inhibition of AChE in the presence of two carbamate insecticides, methomyl and pirimicarb. IC₅₀ values for methomyl ranged from 0.35 to 2.4 μM, while six out of eight colonies had lower values that ranged from 0.16 to 0.30 μM for pirimicarb. Two colonies that were inhibited by methomyl had very high IC₅₀ values for pirimicarb, 40.4 and 98.6 μM respectively. The target-site insensitivity in these two colonies that are resistant to pirimicarb could be due to an ace2 gene mutation. This is the first instance where MACE phenotypes in M. persicae from the United States were studied and confirmed. The results indicate that the possible insensitivity due to MACE resistance in some colonies may render selected carbamate insecticides ineffective. Concerns of MACE resistance in managing the tobacco-adapted form of the green peach aphid on tobacco in the United States are discussed.     

Monitoring of inflights of green peach aphids,Myzus persicae (Sulzer), in New Brunswick potato fields by yellow pans from 1974 to 1983: Results and degree-day simulation

Based on 10 years of trapping with yellow pan traps it was determined that on the average inflights of green peach aphids,Myzus persicae (Sulzer), start July 26 and cumulative catches of more than five aphids August 8. The lack of significant differences in the timing of first and cumulative catches of aphids between the northern and the southern section of the potato production area is additional evidence thatM. persicae does not usually overwinter in New Brunswick. Important yearly variations in the timing of the first cumulative catch of more than 5 aphids can be simulated by the thermal summation of 1188 DD and forecasted by regression on the timing of first inflights. The use of these results to improve the extension program is discussed.     

Interactions between Metopolophium festucae cerealium (Hemiptera: Aphididae) and Barley yellow dwarf virus (BYDV-PAV)

Interactions between an invasive aphid, Metopolophium festucae (Theobald) subsp. cerealium, and Barley yellow dwarf virus (BYDV-PAV) were studied under laboratory conditions. M. festucae cerealium is an economic pest of wheat and barley that has recently been found in high population densities in wheat in the Pacific Northwest of the United States. BYDV-PAV is the most prevalent and injurious species of BYDV worldwide and in the Pacific Northwest. Although M. festucae sensu stricto (Theobald 1917) has been reported previously as a vector of some BYDV isolates, there is no confirmed transmission of BYDV by M. festucae cerealium. Two experiments examined the ability of M. festucae cerealium to transmit BYDV-PAV. The first used single aphids caged to indicator plants of a BYDV-susceptible winter wheat cultivar and the second used multiple aphids on each test plant. M. festucae cerealium did not transmit BYDV-PAV in either experiment, whereas transmission by a known BYDV vector, Rhopalosiphum padi L., was consistently high (≥93%). A third experiment compared the intrinsic growth rate, days until first reproduction and daily reproduction by M. festucae cerealium on sham-inoculated and BYDV-PAV-infected wheat, but detected no differences. The findings are reviewed in light published data on M. festucae species, BYDV transmission, and the potential pest status of this new invading aphid.     

Multi-generational Effects of Different Resistant Wheat Varieties on Fitness of Sitobion avenae (Hemiptera: Aphididae)

Crop resistance plays a role in preventing aphid damage, benefiting food production industries, but its effects are limited due to aphid adaptation and phenotypic plasticity. Therefore, furthering understanding of aphid–crop interactions will improve our ability to protect crops from aphids. To determine how aphids adapt to resistant varieties of wheat, Triticum aestivum L. over time, we performed a laboratory experiment to assess the multi-generational effects of three wheat varieties, Batis, Ww2730, and Xiaoyan22, with different resistance levels on the fitness of Sitobion avenae (Fab.) (Hemiptera: Aphididae). The results showed that Ww2730 and Xiaoyan22 were more resistant than Batis to S. avenae, regardless of whether the aphids were newly introduced or had been acclimated before being introduced to the three wheat varieties. However, the effect of resistance on aphid life-history traits was time dependent. Aphid weigh gain increased and they development faster of the acclimated generation compared to the newly introduced generation on all three varieties. And the fecundity on the three varieties and net reproduction rates on Batis and Xiaoyan22 significantly decreased. Aphid fitness in terms of individual life-history parameters improved, whereas aphid fitness in terms of reproductive decreased, and a convergence effect, the difference gaps and standard errors of all life-history traits among the three acclimated populations had narrowed and were less than those in the three first-generation populations, was observed during the 3-mo experimental period. We suggested that S. avenae could rapidly respond to wheat resistance through life-history plasticity.     

Development of resistance to insecticides in the invasive mealybug Phenacoccus solenopsis (Hemiptera: Pseudococcidae) in Pakistan

The mealybug Phenacoccus solenopsis has been a serious pest of cotton, vegetables, ornamentals and other plants since its invasion into Pakistan in 2005. Its susceptibility to commonly-used insecticides was monitored during 2005–2013 by a nymphal dip bioassay. Initially, P. solenopsis was found susceptible to a range of insecticide classes. Lethal concentration values were particularly low for organophosphates and pyrethroids. After a year of its exposure to insecticides, P. solenopsis developed moderate to high levels of resistance to pyrethroids. After two years, resistance to organophosphates methidathion and chlorpyrifos also rose to moderate to high levels. After five years of use, resistance to pyrethroids, organophosphates, neonicotinoids, endosulfan, carbosulfan, and thiocyclam was generally high to very high. Acetamiprid resistance was slow to develop, as it reached moderate level of resistance after seven years of its extensive applications. Insecticide resistance in P. solenopsis could have been managed in Pakistan if the effective and diverse insecticides were used in rotation, along with other integrated pest management tactics, at the initial stages of resistance development.     

Field efficacy of wintertime insecticide applications against greenbugs, Schizaphis graminum (Rondani) (Hemiptera: Aphididae) on winter wheat (Triticumaestivum L.)

Winter wheat producers in Oklahoma often combine an insecticide with a top-dress application of nitrogen during late fall and winter to control existing greenbug populations. We evaluated the efficacy of three classes of insecticides applied in cold weather field conditions ranging from −13.3 to 28.9 °C from 2002 to 2004 for greenbug control in winter wheat in replicated small plots. Insecticides provided control ranging from 0% to 98%, but generally responded similarly to temperature. Percent control of greenbugs resulting from applications of dimethoate, chlorpyrifos and λ-cyhalothrin was correlated with maximum, minimum and average daily temperatures that occurred two days post-treatment. While percent control was unique for each insecticide, a combined regression of percent control against average daily temperature predicted that a 95% level of control would be achieved when post-treatment temperatures exceeded 13.6 °C. Rainfall that occurred post-treatment affected the efficacy of dimethoate but did not affect the other insecticides. Insecticide persistence was extended under cooler temperatures, allowing acceptable control 14 days post-treatment if temperatures warmed. The decision to apply insecticides should be made based on existing treatment thresholds for greenbug, but if treatment with an insecticide is warranted, winter wheat producers can expect reasonable control of greenbugs from insecticides applied during the winter, as long as post-treatment temperatures exceed 13 °C within the following 14 days.     

Rate of spread of PVYn by alateMyzus persicae (Sulzer) from infected to healthy plants under laboratory conditions

Summary Alate green peach aphids,Myzus persicae (Sulzer), tested in a flight chamber during their maiden flight period displayed behaviours ranging from repeated trivial flights to settling on the plants. The interaction of alate vector density and PVYⁿ spread was dichotomous, virus spread was significantly related to vector density in some trials but virus spread was nil or limited and not significantly dependent on vector density in others. The green peach aphid colony used in these experiments provided a mixture of active and highly active alate populations. Results suggest that inactive and active vectors came from the active and highly active alate populations, respectively. Therefore, winged aphids within a species cannot all be attributed the same vector efficiency unless known to originate from the same population. At a 15% inoculum level the intercept for the regression model for the spread of PVYⁿ was 5.03% indicating that there is a significant probability of propagation at aphid densities as low as one. However, over the range of aphid densities tested, the rate of spread per aphid was low, 0.08%, suggesting that reinfection of newly infected plants or movement interference between aphid vectors rapidly became important factors negatively affecting virus spread. Although these results cannot be directly transferred to field conditions they provide confirmation that lowM. persicae numbers can transmit unacceptable levels of mosaic and that low inoculum levels are required to decrease the risk of transmission by the small aphid numbers which cannot be realistically controlled.     

大豆蚜内共生菌groEL克隆及表达水平分析

为了解大豆蚜(Aphis glycines Matsumura)传播的大豆花叶病毒(soybean mosaic virus,SMV)与其体内共生菌产生的病毒结合蛋白(Gro EL)之间的作用机制,运用RT-PCR技术克隆得到大豆蚜内共生菌groEL基因全序列,把该基因与pET21b载体重组后进行原核表达,经Ni-Agarose His亲和层析得到纯化的蛋白,并利用荧光定量PCR技术分析了饲毒不同时间、不同龄期大豆蚜内共生菌gro EL基因表达量的变化。序列分析表明:大豆蚜内共生菌groEL基因全长序列为1 647 bp,编码548个氨基酸,推测蛋白分子量和pI值分别为69 k Da和5.24,成功构建重组载体pET21bGro EL进行原核表达,Western-blot鉴定确定为目的蛋白,蛋白可溶性分析发现重组蛋白为包涵体。随饲食SMV时间的延长大豆蚜内共生菌groEL的表达量显著增加,且无翅成虫与有翅成虫内共生菌groEL的表达量显著高于其它4个若虫期。大豆蚜内共生菌groEL基因能在原核细胞中稳定、正确表达,并且大豆蚜在饲食SMV后会诱导其内共生菌gro EL的表达,从而增加SMV爆发流行的可能性。     

Pea Aphids (Hemiptera: Aphididae) Have Diurnal Rhythms When Raised Independently of a Host Plant

Seasonal timing is assumed to involve the circadian clock, an endogenous mechanism to track time and measure day length. Some debate persists, however, and aphids were among the first organisms for which circadian clock involvement was questioned. Inferences about links to phenology are problematic, as the clock itself is little investigated in aphids. For instance, it is unknown whether aphids possess diurnal rhythms at all. Possibly, the close interaction with host plants prevents independent measurements of rhythmicity. We reared the pea aphid Acyrthosiphon pisum (Harris) on an artificial diet, and recorded survival, moulting, and honeydew excretion. Despite their plant-dependent life style, aphids were independently rhythmic under light–dark conditions. This first demonstration of diurnal aphid rhythms shows that aphids do not simply track the host plant’s rhythmicity.