Control efficacy of Bacillus thuringiensis and a new granulovirus isolate against Cydia pomonella in orchards

Abstract

Codling moth, Cydia pomonella, is one of the most serious pests of apple and pear worldwide. This study evaluates the efficacies of a granulovirus, a Bacillus thuringiensis (Bt) strain and their combination in the control of C. pomonella in China. A Cydia pomonella granulovirus (CpGV) was isolated from C. pomonella cadavers in an orchard in Gansu, China. Droplet-feeding bioassays showed the median lethal concentration (LC₅₀) of this CpGV isolate (CpGV-C1) against the third instar C. pomonella larvae was 770 OBs µl^?1. The LC₅₀ values of Bt C-33 and kurstaki HD-1 against the third instar larvae were 26.3 µg ml^?1 and 15.7 µg ml^?1, respectively. Field tests indicated the control efficacies of CpGV-C1 and the combination of CpGV-C1 and Bt against C. pomonella larvae in apple orchards were similar to that of beta-cypermethrin. Our data demonstrated that the combination of CpGV and Bt might effectively protect apple fruits from the damage of C. pomonella larvae and had the potential to be developed as a low-cost, highly effective insecticide.     

苹果蠹蛾成虫在苹果园中的动态分布

为了解苹果蠹蛾Cydia pomonella(L.)在田间的空间分布格局及其季节变化,从而为基于不同果园特点的诱捕器监测及有害生物综合治理提供基础信息,2005及2010年,本研究选择甘肃高台县和张掖甘州区的两处果园,应用地统计方法对其中的成虫空间分布及其季节性变化进行了研究。其结果显示:在采取常规防治的果园中,苹果蠹蛾发生热点集中在果园的边缘,且随着成虫数量季节性的消长,这种边界效应变的更加突出;而在采取了迷向防治措施的果园当中,诱捕器捕获量的空间相关性与信息素浓度和虫口数量有密切的关系。根据以上研究结果,在今后的监测工作中,尤其是在较大的果园中进行诱捕器布局的时候,应将果园的边缘地区作为重点监测区域。     

苹果蠹蛾颗粒体病毒CpGV-CJ01的分离和鉴定

苹果蠹蛾颗粒体病毒(Cydia pomonella granulovirus,CpGV)是控制苹果蠹蛾Cydia pomonella(L.)种群的重要生防因子。商业化产品病毒株单一,抗性的快速产生会降低CpGV的防效,高毒力或与之具有遗传差异的新病毒株可用于延缓病毒抗性的产生或发展,对苹果蠹蛾的控制策略具有重要作用。本研究从中国酒泉地区苹果园中的苹果蠹蛾野生种群及其实验室种群发病虫体中分离获得一株致病病毒,通过幼虫发病特征、病毒包涵体的形态学及分子生物学方法共同证实该病毒株为CpGV,且与CpGV-M相似,将其命名为CpGV-CJ01。其幼虫的发病体征具有CpGV感染的典型症状,包涵体的电镜形态学观察结果符合CpGV结构特征,利用分子生物学方法克隆得到Granulin基因和凋亡抑制蛋白基因(inhibitor of apoptosis protein,iap)均与CpGV-M具有99%以上的相似性,但是对于毒力的准确定量需要做进一步研究。我国新病毒株的发现为我国开展苹果蠹蛾颗粒体病毒的生物学防治创造了先决条件,并可作为延缓世界范围内CpGV抗性的候选菌株。     

甘肃省苹果蠹蛾卵的空间分布格局

为准确掌握苹果蠹蛾Cydia pomonella(L.)的田间发生动态,本文对苹果园中苹果蠹蛾卵的空间分布格局和抽样技术进行了研究。结果表明:在第2代卵发生高峰期,苹果叶片上的苹果蠹蛾卵量显著高于果实上的卵量(叶片上着卵量占总卵量的58.2%,P<0.05),叶片上的卵主要分布于叶片正面(正面着卵量占叶片上总卵量的69.6%,P<0.05);在树冠不同方位上,东、南两面的着卵量最大,但在不同空间层次上分布的卵量没有差异。卵在叶片和果实上均呈聚集分布,且聚集强度随种群密度的升高而增加,其聚集是由环境因素造成的。文中还根据Taylor幂法则参数建立了苹果蠹蛾卵的理论抽样数模型。     

Isolation of microsatellite loci in the codling moth,Cydia pomonella (Lepidoptera: Tortricidae)

Cydia pomonella L. is an important insect pest of pome fruits worldwide. We have isolated and characterized 17 microsatellite loci from the enriched genomic libraries constructed using a biotin/streptavidin capture protocol. Among these loci, 11 were scored polymorphic when 50 individuals from a laboratory population were screened. Their alleles numbered two to four, with the observed heterozygosity (H_O) ranging from 0.114 to 0.404. Successful amplification was obtained for all these loci when the designed primers were tested, showing the promise of use in genetic mapping and population studies.     

Mapping the disjunct distribution of introduced codling moth Cydia pomonella in China

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Ultraviolet protection of the Cydia pomonella granulovirus using zinc oxide and titanium dioxide

Cydia pomonella granulovirus (CpGV) is a specific pathogen of codling moth, the most serious pest of apple worldwide and has recently been isolated in China. However, its use for codling moth control is limited by ultraviolet (UV) solar radiation, which is a major factor affecting the field persistence of this virus. The virion is occluded in the granulin matrix of occlusion bodies. Many substances have been tested as sunscreen agents, but little has been published on the use of reflectors with the occluded bodies (OBs) of CpGV. This work investigates the susceptibility of a native GV, CpGV-ZY, to UVB radiation over different time periods and evaluates the protective effect of two sunscreen agents, zinc oxide (ZnO) and titanium dioxide (TiO₂). Laboratory tests showed 10⁴ OB/ml of CpGV-ZY exposed to UVB light (3.5 W/m²) for 3.75 h caused 50% inactivity. At 15 mg/ml ZnO and 10 mg/ml TiO₂, the mortality was highest after 4-h exposure to UVB light. Semi-field tests indicated both compounds are effective as UV protectants at low concentrations. These are the first results confirming that ZnO and TiO₂ hold promise as UV protectants for this CpGV-ZY isolate. Moreover, it is apparently safe and effective to use within the range of concentrations needed for codling moth control.     

EAG measurement of pheromone distribution in apple orchards treated for mating disruption of Cydia pomonella

Pheromone concentrations were measured in an apple orchard using an advanced EAG device featuring short-term recalibration of the antenna with two calibration standards, a lightweight remotely operated probe and automated measurement cycles. The effects of wind direction on pheromone density and distribution at the edge of the orchard were studied as well as the change of pheromone density with height from 1 to 6.5 m. Results show that pheromone can be found at heights of up to 6 m when moderate winds are present. Very low wind speeds tend to reduce the height of the pheromone cloud. Clean wind entering the orchard creates a transition zone up to 15 m wide where the pheromone is depleted. At the down-wind edge of the orchard, pheromone signals were recorded at distances of up to 60 m downwind from the treated zone at concentrations in the same order of magnitude as within the treated orchards. The consequences of these results concerning the design and interpretation of mating disruption field tests are discussed.     

Spatial discrimination of pheromones and behavioural antagonists by the tortricid moths Cydia pomonella and Adoxophyes orana

Male moths responding to their species-specific sex pheromone, may cease their upwind flight when pheromone components of sympatric species are added to the mixture. The interspecific interaction between the pheromone response of the tortricid moths Cydia pomonella and Adoxophyes orana was investigated in field-trapping and wind-tunnel studies. Addition of the A. orana pheromone [(Z9)-tetradecenylacetate and (Z11)-tetradecenylacetate] to a source containing the C. pomonella pheromone [(E8, E10)-dodecadienol] resulted in a significant inhibition of attraction by male C. pomonella. It is demonstrated that this behavioural antagonist for C. pomonella must be emitted from the same point source to induce this inhibitory effect. A spatial separation of the two interspecific pheromones (at 14 cm, 5 cm and 0.5 cm crosswind) restored the attraction of the conspecific pheromone for male C. pomonella. In contrast to C. pomonella, male A. orana were not inhibited by point sources releasing both the C. pomonella and A. orana pheromone. We suggest that the discrepancy in the interspecific pheromone interaction between these two tortricids can be explained if we consider the evolutionary ecology of interspecific pheromone communication in C. pomonella and A. orana. Accepted: 18 July 1999     

Antennal and behavioural response of codling moth Cydia pomonella to plant volatiles

Identification of host volatile compounds attractive to codling moth Cydia pomonella, a most important insect of apple, will contribute to the development of safe control techniques. Synthetic apple volatiles in two doses were tested for antennal and behavioural activity in codling moth. Female antennae strongly responded to (Z)3‐hexenol, (Z)3‐hexenyl benzoate, (Z)3‐hexenyl hexanoate, (±)‐linalool and E,E‐α‐farnesene. Two other compounds eliciting a strong antennal response were the pear ester, ethyl (E,Z)‐2,4‐decadienoate, and its corresponding aldehyde, E,E‐2,4‐decadienal, which is a component of the larval defence secretion of the European apple sawfly. Attraction of codling moth to compounds eliciting a strong antennal response was tested in a wind tunnel. Male moths were best attracted to a blend of (E,E)‐α‐farnesene, (E)‐beta‐farnesene and ethyl (E,Z)‐2,4‐decadienoate. The aldehyde E,E‐2,4‐decadienal had an antagonistic effect when added to the above mixture.     

The occurrence and distribution of resistance of codling moth to Cydia pomonella granulovirus in Europe

Thirty‐five codling moth (CM, Cydia pomonella L., Lepidoptera, Tortricidae) populations collected in different commercial orchards in six European countries were tested for their susceptibility to Cydia pomonella granulovirus (CpGV‐M). Including previously published data on CpGV‐M resistance, a total of 38 CM colonies showed considerably elevated LC₅₀ values, independent of the country origin. When only few test individuals are available, determination of mortality of neonate larvae at a discriminating concentration range of 10⁴ to 10⁶ OB/ml (>log4) as a direct measure of percentage susceptible individuals in a CM population is more advisable than calculation of LC₅₀ values. The >log4 mortality alone or in combination with the LC₅₀ value can be used for identification of resistance in a population. Results indicated a locally separated but widely spread occurrence of CM populations with low susceptibility to CpGV‐M. The most plausible hypothesis for the emergence of CpGV‐M resistance is its selection by repeated use of CpGV products.     

不同剂型迷向剂处理对苹果蠹蛾控制效果比较

【背景】苹果蠹蛾是我国重要的检疫性害虫,目前从新疆迅速向东部扩散。苹果蠹蛾性信息素胶条迷向剂对防控苹果蠹蛾高效、安全,但成本较高。【方法】2013年在宁夏中卫市常乐镇马路滩村果园使用3种不同剂型的迷向剂对苹果蠹蛾进行了防治试验,每个处理果园面积3.3 hm~2,分别使用性诱剂处理后,用诱捕器监测处理后的诱蛾量,在生长期调查果实为害率,比较防治效果。【结果】通过整个生长季诱捕器监测,悬挂点以900个·hm~(-2)双层处理,胶条迷向剂在开花前处理1次,整个生长季处理区中心部位没有监测到苹果蠹蛾成虫;透明塑管迷向剂分别在开花前和6月底处理2次,整个生长季中心部位平均每个诱捕器诱到3.3头雄蛾;膏体迷向剂分别在开花前和6月底处理2次,整个生长季中心部位平均每个诱捕器诱到12头雄蛾。在6月下旬和果实采收前进行果实为害率调查,胶条迷向剂区平均蛀果率分别为0和0.56%,透明塑管迷向剂区蛀果率分别为0.89%和1.38%,膏体迷向剂处理区蛀果率分别为0.79%和1.38%。常规农药防治区2个时期蛀果率分别为1.44%和3.13%。【结论与意义】综合考虑防治效果和使用成本,在虫口密度高、效益高的果园可以使用胶条迷向剂,膏体迷向剂和透明塑管迷向剂只有在虫口密度较低的情况下使用。     

Mapping of pachytene bivalents of female codling moth Cydia pomonella (Linnaeus) (Lep., Tortricidae)

Spread pachytene nuclei of codling moth Cydia pomonella (Linnaeus) (Lep., Tortricidae) females of a Syrian strain (SY) were used to investigate chromomere patterns of chromosome bivalents and determine their length. The karyotype of female codling moths consists of 28 chromosome bivalents, of which seven are clearly distinguishable using chromosome length and the number and size of the chromomeres in the pachytene stage. One autosome bivalent has two nucleolar organizing regions (NORs) that are located at the opposite ends of the chromosome and appear as distinct structural landmarks. In female codling moths, the WZ sex chromosome bivalent was easily identified in pachytene oocytes according to the heterochromatic thread of the W chromosome. This study contributed to the knowledge and identification of pachytene chromosomes of female codling moths.     

Incidence and transmission of a granulovirus in a large codling moth [Cydia pomonella L. (Lepidoptera: Tortricidae)] rearing facility

Incidences of potential per os Cydia pomonella granulovirus (CpGV) transmission within a large codling moth colony were identified. CpGV was detected in the water which is used to wash egg sheets. When pre-neonates were extracted from eggs prior to emergence and tested for the presence of CpGV, 40% were found to carry amounts of CpGV detectable by a polymerase chain reaction (PCR) assay, suggesting possible transovarial transmission of the virus. Although symptoms typical of virus infection and larval death were found infrequently within communal rearing trays, the frequency with which CpGV DNA was detected by PCR assays increased from a mean of 31% of 10-day-old larvae to 94% of 25-day-old larvae. CpGV in codling moth cadavers remained virulent after being held at 60 degrees C for 3 days under conditions similar to the treatment of spent diet at the rearing facility before its disposal. PCR tests of surface samples taken from air filters and rearing rooms of the rearing facility were found to contain CpGV. Bioassays of surface samples from the diet trash bin and a filter through which outside air is passed before entering the rearing chambers resulted in significant codling moth neonate mortality. The virulence of CpGV in dust from the spent diet and the original inadvertent positioning of the diet trash bin directly below one of the air intake ducts are suggested as a possible additional source of CpGV contamination within the facility.     

Effect of radiation on fecundity and fertility of codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) from South Africa

Codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) is the key pest of pome fruit in South Africa, and it’s control in apple and pear orchards relies on the application of insecticides and pheromone‐mediated mating disruption. Development of resistance to insecticides and placement of restrictions on the use of certain insecticides has made control of codling moth in South Africa increasingly problematic. The use of the sterile insect technique (SIT) as a control tactic for codling moth is under investigation as a potential addition to the current control strategy. We investigated the radiosensitivity of a laboratory strain of codling moth that was established from moths collected from commercial and organic orchards in the Western Cape, South Africa. Fecundity and fertility of this strain following radiation were consistent with values for the codling moth strain in the Canadian rearing facility in British Columbia. For both strains, the female codling moth was considerably more radiosensitive than the male. At a radiation dose of 100 Gy or higher, treated females were 100% sterile. The fertility of the South African strain was higher (86.3%) than for the Canadian strain (71.9%). This difference in fertility between the two strains was maintained when the dose of radiation was 100 Gy. However, the level of fertility was very similar between the two strains for doses ≥150 Gy. Therefore, based upon previously published work and the data from this study, an operational dose of 150 Gy is recommended for future codling moth SIT programmes in South Africa.     

Effect of ecdysone agonists on vitellogenesis and the expression of EcR and USP in codling moth (Cydia pomonella)

The effects of tebufenozide and methoxyfenozide on vitellogenin (Vg) synthesis/release in the fat body, translocation in hemolymph, uptake by the ovary, and the expression of the ecdysone receptor (EcR) and its heterodimer partner, ultraspiracle protein (USP) in fat body, were investigated in Cydia pomonella. The results indicated that both ecdysone agonists significantly increased the Vg level in the adult hemolymph when the moths were exposed to agonist-treated surfaces. However, these agonists did not affect Vg release from the fat body nor Vg deposition in the first batch oocytes. Western blot analysis revealed that the expression of EcR and USP was significantly increased in tebufenozide- and methoxyfenozide-treated samples compared to the control, suggesting that ecdysone agonists regulated the Vg synthesis via the EcR and USP proteins complex.     

甘肃酒泉苹果蠹蛾的发生规律

苹果蠹蛾Cydia pomonella(L.)是我国重要的果树害虫和检疫对象。本文通过田间调查和性诱芯诱捕器诱捕的方法,研究了2008年苹果蠹蛾在甘肃酒泉的年发生规律和空间分布特性。结果表明,苹果蠹蛾在我国甘肃酒泉1年发生2代;越冬代和第1代成虫发生高峰期分别为5月上旬至中旬和7月上旬至中旬,成虫在树冠的中层、向阳的方向(东部和南部)、果实和叶背面产卵较多;幼虫发生的两次高峰分别发生在6月17日和7月26日,刚孵化幼虫很快蛀果隐蔽为害,给防治带来很大困难;幼虫化蛹前,主要从树的上部向下爬行,并常以老熟幼虫潜入树干或分枝的树皮下结茧化蛹或越冬,次年4月中下旬开始羽化。     

Influence of juvenile hormone and mating on oogenesis and oviposition in the codling moth,Cydia pomonella

Oogenesis in the codling moth, Cydia pomonella, and the role of juvenile hormones (JHs) were addressed. Rudimentary ovarian structures were recognisable in day 3–4 pupae, when haemolymph JH was still undetectable by coupled gas chromatography‐mass spectrometry in the selected ion mode (GC‐MS/SIM). The presence of developing oocytes was observed by light microscopy on day 8, coincident with very low JH titres (0.74 ± 0.05 ng/ml JH II). Chorionation was only evident upon emergence, following an increase in JH in the pharate adult (0h old: 4.71 ± 0.34 ng/ml JH II). Analysis of haemolymph from virgin and mated females indicated that JH II was predominant, with approximately equal and lower quantities of JHs I and III (3.3‐ to 5.0‐fold less). When pupae or newly emerged adults were treated with JH homologues, no alteration in ovarian protein content was apparent, but the JH mimetic, fenoxycarb, depressed the number of oocytes filling ≥ 50% follicular volume. Chorion deposition was stimulated by JHs I, II, or III (10 μg), but not by fenoxycarb (0.05 μg, 10 μg). Mating provided correct stimuli for enhanced choriogenesis and egg laying, and, since haemolymph JH titres were concomitantly elevated (approximately 2‐fold), it was postulated that the rise in JH elicited both these events. Application of JHs to virgin females, however, could not mimic mating; only increases in choriogenesis were induced: JH‐treatment of virgins (or mated insects) significantly decreased oviposition rates over 24 and 48 h and markedly reduced the life‐time total number of eggs. Arch. Insect Biochem. Physiol. 41:186–200, 1999. © 1999 Wiley‐Liss, Inc.