Efficacy of Bacillus thuringiensis against Phyllocnistis citrella (Lepidoptera: Phyllocnistidae)

The purpose of this work was to analyze the efficacy of Bacillus thuringiensis Berliner on the control of Phyllocnistis citrella Stainton (Lepidoptera: Phyllocnistidae) in laboratory and field trials. In the laboratory, four B. thuringiensis were used: Dipel (commercial formulation) tested at the concentrations of 25 x 10(6) and 25 x 10(8) spores/ml and the isolates K, 6, and 15 (collections of the University of Azores) at the concentration of 25 x 10(6) spores/ ml. A surfactant solution of nonoxinol also was tested with or without the different suspensions of B. thuringiensis. Leaves of Citrus sinensis (L.) Osbeck with second or third instars of leafminer larvae were used in all tests. Bacterial suspensions were applied topically on the surface of intact leaf mines or by injection inside the mine, near the head of the leafminer. When injecting both concentrations of Dipel into the mines, mortality of the leafminers increased compared with the topical application, although no significant differences were observed. The addition of the nonoxinol to the Dipel suspension, applied topically, increased the effect of B. thuringiensis, but differences were not significant. The mortality of the leafminers treated only with the nonoxinol solution increased significantly 48 h after treatment, compared with the control group, suggesting an insecticidal effect of this surfactant when used at a concentration of 0.01%. All the tested B. thuringiensis were equally active against the leafminer, either when applied topically or by mine injection. Field trials showed a significant difference between larval mortality of the control group and the results observed at the trees treated with B. thuringiensis 48 h after treatments.     

印度查谟地区甜橙上柑桔潜叶蛾为害动态及其与重要气候因子的关系(英文)

本研究旨在揭示印度查谟柑桔潜叶蛾Phyllocnistis citrella Stainton为害甜橙Citrus sinensis的季节性变化,以及降雨量、相对湿度和温度等重要的气候因子对其种群的影响。本文对不同季节印度查谟的一个甜橙园里的柑桔潜叶蛾丰度进行了调查, 从2005年3月到2008年2月每两周调查一次。柑桔潜叶蛾在一年内有3个为害高峰,分别是4月中旬、7月中旬和9月中旬,这与甜橙新营养梢的生长期相吻合。相关分析表明,上午和下午的相对湿度和平均相对湿度与柑桔潜叶蛾的数量呈负相关;然而,平均降雨量、最高气温、最低气温和平均气温与柑桔潜叶蛾的数量呈正相关。降雨量和温度与柑桔潜叶蛾为害程度呈显著正相关。总之,柑桔潜叶蛾的数量不能简单地通过观察某一特殊地区的相对湿度来预测,而降雨量和温度在影响虫害方面均起着重要的作用。     

一种快速鉴别柑橘潜叶蛾蛹及成虫雌雄的简易方法

【目的】柑橘潜叶蛾Phyllocnistis citrella Stainton是柑橘重要害虫,本研究拟建立一种快速鉴别柑橘潜叶蛾蛹及成虫性别的简易方法。【方法】利用体视显微镜观察、拍照记录柑橘潜叶蛾蛹和成虫的腹部末端形态特征并进行比较分析,待蛹羽化后进行解剖验证结果。【结果】与柑橘潜叶蛾雄蛹相比,雌蛹的第7腹节下缘分界线不明显,生殖孔和肛门分别在第8腹节和第10腹节,而雄蛹的第7腹节下缘分界线明显,生殖孔在第9腹节,肛门在第10腹节。柑橘潜叶蛾雌成虫腹部末端呈圆筒形,而雄成虫腹部末端相对尖细;轻轻按压成虫腹部,雌蛾在末端伸出部分的两侧有黑斑,而雄蛾在末端伸出部分的两侧没有黑斑,但有一对长毛簇,在伸出的同时散开。该方法能快速鉴别柑橘潜叶蛾蛹及成虫的性别,其准确率为100%。【结论】通过比较柑橘潜叶蛾雌雄蛹生殖孔及肛门的位置,可以准确区分雌雄蛹;轻压并观察雌雄成虫腹部伸出末端黑斑或长毛簇的有无可有效区分成虫性别。     

Parasitism in Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) in Citrus orchards in Montenegro, RS, Brazil

Phyllocnistis citrella Stainton, the citrus-leafminer, is an important pest of citrus worldwide. Knowledge of natural parasitism levels is fundamental to the establishment of tactics of management and control of this species. This work aimed to evaluate the parasitism in two citrus orchards, one of 'Montenegrina' (Citrus deliciosa Ten.) and the other of 'Murcott' (C. sinensis (L.) Osbeck x C. reticulata Blanco), located in Montenegro, RS. In fortnightly samplings, from July/2001 to June/2003, all leaves containing P. citrella pupae from randomly selected plants were collected and maintained individually until emergence of the parasitoids or the citrus-leafminer. Parasitism was calculated considering the number of emerged parasitoids relative to the total number of emerged individuals. Correlation and linear regression tests were done to evaluate the relationship and the influence of biotic and abiotic factors upon the parasitism index. In both orchards the greatest parasitism percentage was registered on autumn in both years. The total percentage was 36.2% in 'Murcott' and 26.4% in 'Montenegrina' in the first year, and 30.2% and 37.6%, respectively, in the second year. In 'Murcott', this index did not differed between the years (chi2 = 2.06; df = 1; P > 0.05), in 'Montenegrina' the parasitism was significantly higher in the second year (chi2 = 7.36; df = 1; P < 0.05). The correlation and linear regression tests indicated a strong influence, in the parasitism index, of the host populational density registered in the previous 45 and 135 days.     

Studies on the interference among larvae of the citrus leaf miner,Phyllocnistis citrella stainton (lepidoptera: Phyllocnistidae)

Observation of the citrus leaf miner, Phyllocnistis citrellaStainton suggested that contacts among larvae frequently occur and either of two larvae encountered is sometimes killed by the interference. A model to describe the competitive interactions in the process of interference was constracted with this species. The distribution of hatchling on an area was considered in the model. The model was based on that of encounters in randomly moving particles in two dimensions. First the time when first death occurs was calculated and n hatchlings were reduced to n−1. Further calculation was made to obtain the time that next death occurs. Such calculation was repeated until the number of larvae was reduced to 1 or the area of mine attained to the completed size. By the simulation based on the data observed on the citrus leaf miner, the numbers of survivors were calculated at different hatchling densities and on different leaves in size. Based on this simulation analysis it was suggested that the following characteristics observed in the present studies enable the maximul number of individuals to become adults.

1. When two hatchlings occur on a leaf, they tend to be separated by the midrib. This implies that female moths tend to reject to lay eggs on the area which has already contained the egg.
2. The larva sometimes avoids the contact immediately before it occurs.
3. The larval mortality caused by a contact is reduced with the larval growth. Since the frequency of contacts increases as the mine is enlarged, the change to high survival prevents the larva from high mortality caused by the increase of contacts.
4. The larval survival does not decrease in spite of the reduction of the area available for mining.

     

Seasonal variation of immature stages of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) in Citrus sinensis orchards under two management systems

Phyllocnistis citrella Stainton is considered an important pest of citrus, causing both direct (reduction on the photosynthetic area) and indirect damage (facilitation of invasion by bacteria that cause citrus canker). The lack of information about the population dynamics of P. citrella, considering the cultivation systems and varieties grown in citrus orchards in Rio Grande do Sul, Brazil, motivated this study. It aimed to evaluate the seasonal variation of immature stages of P. citrella, from June 2002 to July 2003, in two orchards of Citrus sinensis, cv. 'Valencia', one maintained according to organic management principles and the other under conventional ones. Fortnightly samplings were carried out, being one shoot collected from each one of 27 randomly chosen plants. The leaves were analyzed for the presence of eggs, larvae, pupae and mines of P. citrella. Leafminer was recorded from October 2002 to April 2003 in the organic orchard, and from November 2002 to July 2003 in the conventional one. A relationship between population size and resource availability (young leaves) was observed. However, population establishment does not depend exclusively on the existence of resources, but also on suitable climatic conditions. This was evidenced by the absence of attacks on the first shooting, which began in late winter. Meteorological factors and resource availability as a whole explain about 64% and 53% of the observed variation in the population size of P. citrella, respectively in the organic and conventional orchards.     

(5Z, 7E)-5,7-Dodecadien-1-ol: Female Sex Pheromone of the Pine Moth Dendrolimus spectabilis Butler

The sex pheromone of the pine moth Dendrolimus spectabilis Butler was tentatively identified as 5,7-dodecadien-l-ol by the use of the electroantennogram technique. Analyses of abdominal tip extracts of virgin females by gas-liquid chromatography and mass spectroscopy showed the presence of a (5Z, 7E)-isomer and a (5E, 7E)-isomer in the ratio of about ca. 5:1. In field examinations with four synthetic isomers of 5,7-dodecadien-l-ol, only traps baited with the (5Z, 7E)-isomer captured an appreciable numbers of male moths.     

Stereoselective Synthesis of (Z,Z)-3, 13-Octadecadienyl Acetate,the Attractant for Smaller Clear Wing Moth

(Z)-3-Hexene-1, 6-diol, a new synthon for the synthesis of (Z)-olefinic pheromones, was prepared from 1, 4-cyclohexadiene. This synthon was used in the synthesis of (Z, Z)-3, 13-octadecadienyl acetate, whose high stereochemical purity at C–3 was essential in attracting male Synanthedon tenuis Butler.     

A novel pheromone dispenser for mating disruption of the leafminer Phyllocnistis citrella (Lepidoptera: Gracillariidae)

The sex pheromone of the leafminer Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) was deployed in a Florida citrus (Citrus spp.) grove by using a novel deployment device (IFM-413) containing SPLAT, a flowable formulation of an emulsified wax compound designed to provide slow release of semiochemicals. The device consisted of two disks connected by string. Each disk was loaded with 1 g of SPLAT containing either 0.15% (Z,Z,E)-7,11,13-hexadecatrienal (triene) or 2% (Z,Z)-7,11-hexadecadienal (diene). The devices were deployed using a two-dimensional multivariate design to determine the optimal rate of pheromone per unit area and degree of aggregation of the deployment devices (number of trees treated per unit area). The IFM-413 device proved effective at becoming securely entangled in tree branches. Furthermore, the devices effectively delivered pheromone-loaded SPLAT that resulted in disruption of trap catch of male P. citrella. Response surfaces showed a quadratic response of trap catch disruption to both total amount of pheromone per unit area and the degree of aggregation of the deployed devices (number of treated trees per unit area). The response surfaces for 0.15% triene or 2.0% diene were similar. The diene produced an effect similar to that of the triene at approximately 13 times the rate of the triene. The greatest disruption of trap catch occurred when the number of treated trees per unit area was greatest (no aggregation of deployment devices). Manufacturing, packaging, and mechanical deployment of the devices remain to be investigated.     

Spatial distribution of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) larvae in three scales.

The spatial distribution of larvae of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), the citrus leaf miner, in leaves, shoots, and tree crowns of Montenegrina tangerine (Citrus deliciosa Tenore) and Murcott tangor (Citrus sinensis L. Osbeck x Citrus reticulata Blanco) was determined. Fortnightly samplings from July/2001 to June/2003, in orchards located in Montenegro (29 degrees 68' S and 51 degrees 46' W), RS, Brazil, were carried out. At each sampling occasion eighth shoots randomly selected were collected. The spatial distribution pattern of P. citrella larvae between tree crowns and in the shoots was aggregated in most sampling occasions in both citrus species. Nevertheless, on the leaves, this pattern followed a random distribution, as indicated by the indices I, Idelta and k parameter.     

Towards the identification and synthesis of the sex pheromone of the citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae)

The objective of this work was to characterize the sexual behavior of the citrus leafminer, Phyllocnistis citrella Stainton, as the foundation for the isolation, identification, and synthesis of the complete sex pheromone of this species. Mating occurred in a time window of 2h, starting 1h before the onset of photophase. The large majority of tested insects mated in the first two days after emergence, with no significant difference between mating at day 1 and day 2. A stereotypical courtship and copulation behavior were described for this species. When mating was successful, the copulation was recorded in average for 49.6 min. In Y-olfactometer tests conducted at the time of mating activity, males were strongly attracted to caged virgin females as well as to extracts from putative pheromone glands.     

合成性信息素对柑桔潜叶蛾的田间引诱作用

目前柑桔潜叶蛾的防治主要依赖化学农药, 而且生产中缺少有效测报技术。为此, 我们于2009年6月30日至10月6日在浙江宁波通过有机合成柑桔潜叶蛾Phyllocnistis citrella（鳞翅目, 细蛾科）的3种性信息素化合物顺7, 顺11, 反13-十六碳三烯醛、顺7, 顺11-十六碳二烯醛和顺7-十六碳烯醛, 配制成不同浓度比例的混合物, 进行田间试验比较其引诱活性。结果表明, 单一的顺7, 顺11, 反13-十六碳三烯醛对柑桔潜叶蛾雄蛾就可以显示较强的引诱作用, 而顺7, 顺11-十六碳二烯醛单一成分没有引诱活性, 顺7, 顺11, 反13-十六碳三烯醛与顺7, 顺11-十六碳二烯醛的二元混合物30∶1~3∶1之间活性较强, 而在30∶1的质量比例时诱虫量最高。含顺7-十六碳烯醛的三元混合物, 当顺7, 顺11, 反13-十六碳三烯醛∶顺7, 顺11-十六碳二烯醛∶顺7-十六碳烯醛三者比例为100∶10∶3时有显著增效作用。剂量与诱捕活性试验显示每枚诱芯1 mg顺7, 顺11, 反13-十六碳三烯醛的剂量引诱作用最强, 随浓度降低, 引诱作用下降。诱捕器在0.8~1.5 m之间的不同悬挂高度对诱捕数量无显著影响。结果说明, 顺7, 顺11, 反13-十六碳三烯醛、顺7, 顺11-十六碳二烯醛和顺7-十六碳烯醛组成的三元混合物诱芯可以作为柑桔潜叶蛾的诱杀技术并应用于其生物防治和预测测报。     

Effect of temperature on development and survival of the parasitoid Pnigalio pectinicornis (Hymenoptera: Eulophidae) reared on Phyllocnistis citrella (Lepidoptera: Gracillariidae)

Laboratory studies were conducted to assess the effect of temperature on the development and survival of the indigenous parasitoid Pnigalio pectinicornis L. on the citrus leaf miner Phyllocnistis citrella Stainton as host, fed on leaves of Citrus sinensis L. Osbck cultivar Washington navel and Citrus reticulata Blanco cultivar Clementine. Experiments were conducted at five constant temperatures ranging from 15 to 32.5 degrees C, with 60 +/- 10% RH and a photoperiod of 14:10 (L:D) h. The relationship between the developmental rate and temperature was determined using both linear and nonlinear (Lactin's formula) models. Developmental time of immature stages tended to be shorter as the temperature increased the range from 15 to 30 degrees C. Mortality was greater at the temperatures extreme tested. Both linear and nonlinear models provided a reliable fit of developmental rates versus temperature for all immature stages. Developmental thresholds that were estimated by the linear model for eggs were higher than those estimated by the nonlinear model. However, higher values of the low developmental threshold for larva and pupa stage of P. pectinicornis were estimated by the Lactin-2 model than that by the linear model. The potential of these models to predict the phenology of this parasitoid and its biological characteristics found in this study are discussed for its proper use as a biological control agent.     

The Biosynthetic Pathway of (Z)-11-Hexadecenal,the Sex Pheromone Component of the Rice Stem Borer,Chilo sappressalis WALKER (Lepidoptera: Pyralidae)

Lipoxygenase-3, the major component of the enzyme in rice grain, was purified 2980-fold with a yield of 7% from embryos. The purified enzyme had a specific activity of 280 μmol O₂ formed/min per mg protein. This enzyme was inactivated by SH compounds, such as cysteine and glutathione. The inactivation was prevented by the addition of catalase or replacement of the air by N₂ gas. These two treatments were also effective for the stable storage of the purified enzyme. The molecular weights measured by sodium dodecyl sulfate gel and gradient gel electrophoresis were 93,000 and 89,000, respectively, indicating that the enzyme is a single polypeptide chain. The purified enzyme contained 0.73 Fe atom per molecule. The absorption spectrum suggested that the enzyme is a non-heme iron protein. Some similarities in amino-acid composition were observed between rice, soybean, and pea lipoxygenases. The purified enzyme specifically produced 9-d-hydroperoxy-10,12(E,Z)-octadecadienoic acid when linoleic acid was used as a substrate.     

Preference and performance of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) on three citrus hosts: laboratory and field assessment

The relationship between preference and performance is crucial to the ecology and evolution of plant-insect interactions. Oviposition preference and offspring performance were evaluated for a citrus pest, the leafminer Phyllocnistis citrella (Lepidoptera: Gracillariidae), on three of its host plants: lemon (Citrus limon L. Burm.), orange (Citrus sinensis L. Osbeck), and grapefruit (Citrus paradisi Macfadyen) in Tucumán province (northwest Argentina). Choice and no-choice tests were performed in open and enclosed environments, and performance parameters (development time, survival, pupal size, and sex ratio) were estimated from laboratory rearing and 3-yr field sampling data. Parasitism rates were studied in laboratory choice test and field assessments. Preference trends were inconsistent, with lemon receiving more eggs in some tests, whereas no preference was observed in others. Patterns of host use in the field did not show significant differences among species. Leafminer performance, including parasitism and predation rates, was generally homogeneous among host plants. From these results, lemon, orange, and grapefruit seem to represent intrinsically similar resources for P. citrella populations in northwest Argentina, a trend that was accompanied by a lack of consistent oviposition preferences in foraging females. Ecological conditions might be more important than physiological adaptation in shaping a probably labile host ranking in this pest species.