Do anthocorid predators respond to synomones from Psylla-infested pear trees under field conditions?

Because Y-tube olfactometer experiments in the laboratory showed a response of anthocorid bugs to odour fromPsylla-infested leaves, it was of interest to assess its relevance under field circumstances. This was done by measuring the density of predatory bugs on pear trees adjacent toPsylla-infested or control trees that were covered with fine mesh gauze-screens. In this way odours from these caged trees could spread through the screen, while contact with thePsylla prey in the cage was prevented. The density of anthocorid predators around cages with heavily infested trees was significantly higher than around uncaged control trees and around cages containing uninfested or little infested trees. Covering a cage withPsylla-infested trees by an airtight plastic sheet led to an immediate drop in the density of anthocorid predators, whereas removal of the sheet led to predator aggregation again. The results of these field experiments strongly support the hypothesis that anthocorid predators respond to volatile chemicals emanating fromPsylla-infested pear trees.     

Descriptions of two new and one little known species of the genus Cacopsylla (Hemiptera: Psyllidae) on Sorbus japonica (Rosaceae) and an observation of their biology

Three species of the genus Cacopsylla were collected from Sorbus japonica in Japan. Two of them, Cacopsylla elegans and Cacopsylla sorbicoccinea, are described as new species based on adults and fifth (final) nymphal instars. The third species, Cacopsylla midoriae, is newly transferred from the genus Psylla. The adult of C. midoriae is redescribed and the nymph is described for the first time. A key to the species feeding on S. japonica (adults and nymphs) is provided. The three species were observed to coexist on the same tree of S. japonica in northern Kyushu. Such coexistence of psylloid congeners is uncommon in Japan.     

Seasonal colour changes, sexual maturation and oviposition in Psylla peregrina (Homoptera: Psylloidea)

ABSTRACT.

• 1 Colour change is shown to be related to the timing of sexual maturation of P.peregrina Förster. Males become sexually mature and attain their autumnal coloration about 3 weeks before females.
• 2 Upon maturation males migrate down branches into the inner crowns of hawthorn trees. Females show a similar movement as they mature later in the season.
• 3 Seasonal colour changes may serve cryptic functions and are appropriate to the different environments in which adults are found during the season.
• 4 The distribution of overwintering eggs reflects the post maturation distribution of adult psyllids, with eggs being concentrated on old wood towards the base of hawthorn branches.

     

The probing behavior of the summer-form pear psylla

Stylet insertion sites on the leaf surface and leaf cell types fed upon by nymphs and adults of the pear psylla, Psylla pyricola Foerster (Homoptera: Psyllidae) were identified using histological techniques and electronic monitoring of probing and feeding activities. Neither the nymphs nor the adult ingested predominantly from the phloem of Pyrus communis cv. Bartlett. We showed that the pear psylla ingests from all leaf cell types, but that xylem, phloem and bundle sheath cells are more acceptable for ingestion than non-vascular tissues. The possible sensory mechanisms underlying selection of stylet insertion sites on the leaf surface and acceptance of various cell types for ingestion are discussed.

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Résumé Les lieux d'insertion des stylets sur la surface de la feuille et les types cellulaires consommés par les larves et les adultes de Psylla pyricola Foerster ont été précisés par étude histologique et par enregistrement électronique du comportement de piqûre et d'alimentation. Ni les larves, ni les adultes n'ont absorbé de préférence le phloème de Pyrus communis de la variété Bartlett. Nous avons constaté que le psylle du poirier ingère le contenu de tous les types cellulaires, mais que le xylème, le phloème et autre cellules des faisceaux libéro-ligneux étaient préferés aux tissus non vasculaires. La discussion a porte sur les méchanismes sensoriels éventuellement responsables de la sélection des lieux d'insertion des stylets à la surface de la feuille et l'acceptation des différents types cellulaires lors de l'ingestion.

     

Reduction of Pear Psylla Damage by the Predatory Bug Anthocoris nemoralis (Heteroptera: Anthocoridae): The Importance of Orchard Colonization Time and Neighboring Vegetation

This 5-year field study was aimed at assessing the importance of predatory arthropods in suppressing pear psylla, Cacopsylla bidens (Sulc), and reducing damage caused by psylla in pear orchards in northern Israel. Correlative data suggest that Anthocoris nemoralis (Fabricius) is the only naturally occurring predator in the system that may reduce pear psylla damage; densities of other predacious taxa in the system (Araneidae, Orius spp., Chrysopidae and Coccinellidae) were not correlated significantly with psylla numbers in the orchards. However, A. nemoralis entered pear orchards at least a month after the beginning of pear psylla activity, apparently too late to prevent fruit damage. Data suggest that A. nemoralis reproduction is lower on both wild and cultivated pears than on Rhamnus, Laurus and Pistacia trees in nearby woods. Furthermore, A. nemoralis populations build up on the wild trees in March, but appear in orchards only in late May. We propose that planting R. alaternus trees near pear orchards could enhance the level of biological control of pear psylla by A. nemoralis. Preliminary results indeed show that pear psylla densities were lower on pear trees grown near Rhamnus alaternus trees than on distant trees.     

梨园芳香植物间作区中国梨木虱与其天敌类群的相互作用

为探讨间作芳香植物对梨园中国梨木虱与其天敌类群相互作用的影响,在梨园中设置不同种类的芳香植物间作处理,以清耕区为对照,研究不同芳香植物间作区中国梨木虱及其天敌类群组成、种群消长动态、时间生态位的变化,并进行灰色关联度分析。结果表明,不同处理区中国梨木虱及其天敌类群数量和发生频率、组成及时序特征、时间生态位宽度与重叠存在明显差别。在梨树年生长周期中,薄荷间作区的中国梨木虱的时间生态位宽度明显增大,多数天敌的时间生态位宽度显著增加,中国梨木虱与天敌种群发生量分布较均匀,但发生的高峰不明显,时间生态位重叠指数均较大,表现出时序上的同步性和跟随性。孔雀草间作区、罗勒间作区、自然生草区的中国梨木虱的生态位宽度较薄荷间作区小,有明显的高峰期,天敌的生态位宽度较对照大,无明显的高峰期。一些天敌种群如跳小蜂、丽草蛉、茧蜂、姬蜂与中国梨木虱在时序上同步性较大,跟随现象明显;而龟纹瓢虫、异色瓢虫和七星瓢虫等天敌种群与中国梨木虱在时序上同步性较差,跟随现象较弱。灰色关联度分析结果表明,薄荷间作区跳小蜂、孔雀草间作区中华大草蛉、罗勒间作区龟纹瓢虫和中华大草蛉、自然生草区丽草蛉、茧蜂、赤眼蜂对中国梨木虱的影响程度较其它种群大。结果显示,梨园间作芳香植物可能通过改变中国梨木虱及其天敌类群的组成、时序特征和生态位特征等控制中国梨木虱的发生。     

温度和水分对越冬代冬型中国梨木虱存活的影响

中国梨木虱(Psyllachinensis)是危害梨树最严重的害虫之一,严重影响梨树的生长发育和果品产量,掌握环境因素对梨木虱生存的影响对制定有效防控策略具有重要意义.为了了解温度和水分对越冬代冬型中国梨木虱存活的影响,本研究在室内分别测定了2,10,20℃3种温度条件下,有无外源水分对梨木虱的死亡率和存活时间的影响.结果表明,不同温度和水分条件均会影响梨木虱的存活.在相同时间内,随着温度的升高,梨木虱死亡率明显提高,寿命缩短;在所设置温度条件下,当有外源水分时,梨木虱的存活率和寿命提高;而在干燥处理下,梨木虱死亡率明显增加,寿命变短,且随着温度的升高,这一趋势逐渐加重.     

Side effects of diflubenzuron on a pear psylla predator:Forficula auricularia

A series of laboratory, semi-field and field tests showed the high toxicity of diflubenzuron toForficula auricularia L. nymphs, at concentrations of 15 and 20 g a.i./hl registered in various European countries and the United States to controlCydia pomonella L. Diflubenzuron proved more selective using the 10 g/hl concentration registered in France, but several sublethal effects have been observed: morphological abnormalities, reduced weight increase and mobility. Unexpectedly for a chitin-deposit inhibitor, intake was reduced, which became apparent from the beginning of exposure to the insecticide, before the onset of the moulting process. In the semi-field tests, and despite diflubenzuron's slowing down effect on psylla nymphs, the earwig's reduced predatory activity due to the product resulted in greater growth of the psylla populations than without treatment. The field-test confirmed the efficacy ofF. auricularia as a psylla predator, and the relative selectivity of diflubenzuron at the lowest concentration.     

Note on the natural enemies ofPsylla hyalina [Homoptera: Psyllidae] onAlbizia lebbeck

A survey of the natural enemies associated withPsylla hyalina infestingAlbizia lebbeck has revealed 2 primary parasitoids, 1 hyperparasitoid, 5 coccinellids, 1 lygaeid and 3 fungal pathogens, all being new records forP. hyalina.      

Évolution du complexe parasitaire des psylles du poirierPsylla pyri etPsylla pyrisuga [Homoptera: Psyllidae] en vergers dans le sud-est de la france au cours de la période hivernale,printanière et estivale

Résumé Le ?psylle commun du poirier?Psylla pyri (L.) est le ravageur-clé de cette culture en France et dans de nombreux pays d'Europe. Parmi les antagonistes, nous avons étudié l'influence du complexe parasitaire sur la dynamique des populations du ravageur. Ce travail a recours au contr?le visuel des rameaux pour suivre le niveau des populations du phytophage. Une méthode d'isolement de larves de l'h?te au laboratoire est utilisée afin d'évaluer le taux de parasitisme ou prévalence. La parasitofaune est constituée de micro-hyménoptères parasito?des et hyperparasito?des de larves L4 et L5 de psylle.Trechnites psyllae (Ruschka) et dans une moindre mesurePrionomitus mitratus (Dalman) sont les parasito?des qui assurent la régulation dès la 1^re génération du ravageur. L'hyperparasitisme, essentiellement d? àSyrphophagus mamitus (Walker), appara?t plus tard sur l'h?te-relaisPsylla pyrisuga Foerster présent en vergers entre la 1^re et la 2^e génération deP. pyri. Les autres hyperparasito?des,Pachyneuron muscarum (L.),Pachyneuron aphidis Bouche,Dendrocerus psyllarum Dessart,Dilyta subclavata Foerster etDilyta talitzkii Belizin sont encore plus tardifs. Les taux d'hyperparasitisme nuls enregistrés au cours de la 1^re génération deP. pyri laissent escompter d'excellents résultats de la mise en pratique éventuelle d'une méthode de lachers précoces de parasito?des, pour réduire le plut t?t possible les populations du ravageur.