Field evaluation of a botanical natural product against the pear psylla (Homoptera: Psyllidae)

A 2-yr field study was conducted to evaluate a botanical natural product, AkseBio2, for control of pear psylla, Cacopsylla pyri L. (Homoptera: Psyllidae). Three applications were made each year. Whereas the first application was applied at the dormant period (just before the first eggs were deposited by overwintered females), the second and third applications, respectively, were against the first and second summer generations of pear psylla. The first application deterred winterform females from depositing eggs until the clusterbud stage (buds expanded but no blossoms open) of tree development. In the second and third applications, the product reduced the number of psyllid eggs and young (first and second) instars, causing up to 79.4 and 81.1% mortality, respectively. However, it was less active against the older (third-fifth) instars and achieved only up to 52.7% mortality. Reduction in egg laying was greater than that caused by amitraz, the most commonly used conventional pesticide for psylla control in Turkey. There were no significant horticultural changes on treated plants up to 7 d after treatment in any trial, nor was there any phytotoxicity on plant tissue as a result of AkseBio2 treatments.     

Interplant movement by pear psylla (Homoptera: Psyllidae): Effects of sex ratio and reproductive status

Sticky trap catch of pear psylla,Cacopsylla pyricola Foerster, is male biased during the reproductive generations, but not the diapausing generation. In cage studies, we monitored movement by male and female pear psylla between host plants, and tested whether reproductive and diapausing psylla exhibit similar rates of movement. We also experimentally varied sex ratio to determine whether sex ratio affected movement. Male-biased sex ratios prompted increased movement off of the original host by male psylla of the reproductive generations; no such effect was noted for diapausing insects. We interpret these results to indicate that male movements increased under male-biased conditions due to mate-searching activities. There was also evidence in two experiments that severely male-biased sex ratios prompted movement off of the original host plant by reproductive females; this effect may have been due to harassment of ovipositing females by males.     

Pear transformed with a lytic peptide gene for disease control affects nontarget organism,pear psylla (Homoptera: Psyllidae)

The biology and behavior of pear psylla, Cacopsylla pyricola Foerster, on a transgenic clone of 'Bartlett' pear, Pyrus communis L., containing a synthetic antimicrobial gene, D5C1, was compared with that of a nontransgenic parental clone to determine whether there were any nontarget effects. The gene construct also contained the marker gene nptII (aminoglycoside 3'-phosphotransferase II) that encodes for antibiotic resistance to identify transformed plants. The purpose of the original transformation was to enhance pear resistance to the bacterial disease fireblight caused by Erwinia amylovora (Burr.) Winslow et al. The biology and behavior of pear psylla on a transgenic clone were compared with a nontransgenic parental pear clone in short- (< or = 7-d) and long-term (32-d) studies. Short-term studies indicated pear psylla adults preferred to settle and oviposit, and nymphs fed more and developed slightly faster, on transgenic pear compared with nontransgenic pear. In contrast, a long-term study on psylla colony development showed considerably fewer eggs, nymphs, and adults were produced on transgenic pear. Although adults reared on transgenic pear did not have weight affected, females produced fewer eggs and nymphal hatch was significantly reduced on the transgenic pear clone. Our results suggest that pear psylla biology and behavior are initially enhanced on this transgenic pear clone. However, chronic exposure of psylla populations to transformed pear plants that express the nptII marker and lytic peptide genes had detrimental effects on pear psylla reproductive biology. Field studies would be required to determine the specific effects of each gene on pear psylla biology and behavior and whether these effects would be expressed under natural conditions. The four-fold reduction in psylla population levels that resulted on this disease resistant transgenic pear line would be an added benefit to a pear integrated pest management (IPM) program. Overall, this study demonstrates that genetically altering plants to control one particular organism can have unintentional yet beneficial effects against other nontarget pest organisms in agricultural crops.     

Preliminary resistance screening on abamectin in pear psylla (Hemiptera: Psyllidae) in northern Italy

In northern Italy (Emilia-Romagna region), integrated pest management has been used for several years against pear psylla, Cacopsylla pyri L. (Hemiptera: Psyllidae), a relevant pest of pear (Pyrus spp.) trees. After the outlawing of amitraz in 2005, the most common active ingredient involved is abamectin, a mixture of avermectin B1a and avermectin B1b. After the development of C. pyri resistance to azinphos methyl in southern France, we evaluated, by topical application, the different sensitivities to abamectin on C. pyri populations collected in orchards from Emilia-Romagna, where different field strategies were used, with alternative success in terms of pest management. The LC50 values ranged between 1.61 and 28.37 mg/liter, and they revealed variations more related to collection time than to field strategies. The failure of abamectin treatments against C. pyri in some Emilia-Romagna locations is probably unrelated to resistance development, but rather it is related to incorrect pest defense management, which could interfere with pest parasitoids and predators.     

高岭土颗粒涂布对中国梨喀木虱寄主选择、产卵的影响及应用效果

为探索可替代化学药剂防治中国梨喀木虱的措施,开展了高岭土颗粒涂布对其寄主选择、产卵影响及应用效果的研究。分别采用3.5%高岭土水溶液、清水对梨休眠枝和当年生枝叶进行喷雾涂布处理,于24、48、72、96 h监测选择条件下成虫分布情况,于96 h记录选择和非选择条件下各枝条上的卵量。采用高岭土水溶液对梨苗均匀喷雾涂布,通过被害叶率、单叶若虫量、虫龄指数、为害指数对应用效果进行评价。研究结果显示,在选择条件下,经高岭土涂布的枝条上成虫数量明显少于对照,高岭土涂布的枝条上冬型成虫数量在96 h时最低(0.5头/枝),96 h时着卵量(1.83头/枝)显著低于对照(30.83头/枝);高岭土涂布的枝叶上夏型成虫在72 h时最低(1.17头/枝),96 h时着卵量(12.33头/枝)显著低于对照(242.5头/枝);在非选择条件下,冬型和夏型成虫在高岭土涂布的枝条上着卵量(2.83和15.17头/枝)分别显著低于对照(25.17和170.42头/枝);供试植株在接虫45 d后为害最严重,高岭土涂布的植株被害叶率(54.17%)、单叶若虫量(2.29头/叶)、虫龄指数(3.79)、为害指数(0.41)分别显著低于为对照植株(98.61%、11.72头/叶、4.13、0.95)。上述结果表明,高岭土涂布对中国梨喀木虱成虫的寄主选择具有驱避效果,对雌成虫的产卵具有抑制作用;高岭土涂布可限制中国梨喀木虱种群增长,降低危害水平。研究结果为中国梨喀木虱的综合治理提供了现实依据。     

Anterior alimentary canal of the pear Psylla,Psylla pyricola foerster (Homoptera,Psyllidae)

Scanning and light microscopy investigations of the anterior alimentary canal of the pear psylla, Psylla pyricola Foerster (Homoptera: Psyllidae), revealed the morphology of the labium and stylets, as well as the presence of sensory structures and a valve in the precibarium. The labium consists of three telescoping segments with an internal labial groove, which surrounds and supports the stylet bundle. Also a part of the labial groove is the internal labial clamp. The stylet bundle is comprised of paired styliform mandibles and maxillae, which interlock to form the food and salivary canals. The stylet bundle proximal to the labium forms a large loop within a membranous crumena. When fully retracted the coiled stylets are under tension. Stylet extension generates increasing tension so that when retracted the stylets readily recoil within the crumena. Penetration of leaf tissues by the stylet bundle is dependent on the interaction between stylet muscles, opening and closing of the labial clamp, the barbed stylet tips, and the ventral position of the labium. Proximal to the crumena the paired stylets separate and diverge at the entrance of the precibarium, which is formed by the interlocking of the epi-and hypopharynges. There are 18 sensory structures in the precibarium, as well as a precibarial valve. These structures appear to be homologous to similar structures observed previously in aphids and leafhoppers. The morphology and the location of the precibarial sensilla suggest that, like the precibarial sensory organs of aphids and leafhoppers, they are gustatory and probably mediate acceptance or rejection of plant fluids, thus playing a major role in locating tissues for feeding.     

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.

     

Resistance of pear psylla (Cacopsylla pyri L.; Hom., Psyllidae) to deltamethrin and synergism with piperonyl butoxide

Abstract: Topical application bioassays, conducted on French populations of Cacopsylla pyri , showed resistance rates to deltamethrin ranging from 31-fold at the adult stage to 135-fold at the last larval stage. Synergism studies between deltamethrin and piperonyl butoxide (PBO), applied either topically or by tarsal contact with PBO, showed (i) that the rates of synergism were more than 10-fold in all the populations and that they could increase to a thousand-fold in some populations, (ii) that the synergistic effect was present to a similar extent at both the larval and adult stages, (iii) that there was no correlation between the synergistic effect and the resistance rates, and (iv) that no correlation was observed between the dates of collection and the rates of synergism. The results makes it impossible to determine whether resistance to deltamethrin is of genetic origin or results only from the induction of monooxygenases by allelochemical substances present in the food ingested by the species.     

Effects of a particle film on biology and behavior of Diaphorina citri (Hemiptera: Psyllidae) and its infestations in citrus

Studies were conducted to investigate the effects of a kaolin-based hydrophilic particle film, Surround WP, on the biology and behavior of the psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae) and to assess population densities of D. citri in citrus subjected to monthly applications of Surround WP. Laboratory investigations indicated a 3% (wt:vol) suspension of Surround WP in water applied directly was not acutely toxic to eggs, older nymphs or adults. Presence of the dried particle film on leaves interfered with the ability of adults to grasp and walk on citrus leaves. During a 30-s period, adults spent an average of 5 s moving on leaves with particle film compared with 16 s on leaves without particle film. When leaves were inverted, a significantly higher percentage of adults fell or flew from treated leaves (53%) than untreated leaves (16%). In a 12-mo study investigating infestations of D. citri on citrus treated monthly with Surround WP, cumulative reductions of 78% in adult numbers on mature leaves and of 60% in adult numbers on flush shoots (immature leaves) were observed in treated trees compared with untreated trees. Numbers of eggs and nymphs per flush shoot were reduced by 85 and 78%, respectively, in trees treated with particle film. Reductions in infestation levels of D. citri in treated trees were attributed to the negative effects of the particle film on the ability of adults to grasp, move, and oviposit. The suppressive effects of a Surround treatment against adult psyllids were degraded by rain.     

Histochemistry and ultrastructure of the mycetome and its 'symbiotes' in the pear psylla, Psylla pyricola Foerster (Homoptera)

The orange-coloured mycetome of the pear psylla, which comprises a cellular covering membrane, a number of mycetocytes and a central syncytium, contains two kinds of inclusions (micro-organisms-in the literature). As DNA could not be detected in them, their status as micro-organisms is questioned. Both kinds contain protein; one kind contains RNA, and (by electron microscopy) tubule-like peripheral maculae. In spite of their anomalous reactions, the inclusions are probably unusual, degenerate or aberrant microorganisms. The biosome theory is invoked in explanation.     

Biology of Diaphorina citri (Homoptera: Psyllidae) on four host plants

The biology of the citrus psyllid Diaphorina citri Kuwayama was studied at 25 degrees C on four commonly grown citrus and related plants [rough lemon, Citrus jambhiri Lush; sour orange, C aurantium L.; grapefruit, C. paradisi Macfadyen; and orange jessamine, Murraya paniculata (L.) Jack] in the laboratory. The biological characteristics of each life stage are described. The average egg incubation periods on orange jessamine, grapefruit, rough lemon, and sour orange varied very little (4.1-4.2 d). The average nymphal developmental periods on these four host plants were essentially the same except the fifth stadium. Survival of immatures on orange jessamine, grapefruit, rough lemon, and sour orange was 75.4, 84.6, 78.3, and 68.6%, respectively. Female adults lived an average of 39.7, 39.7, 47.6, and 43.7 d on these respective host plants. The average number of eggs laid per female on grapefruit (858 eggs) was significantly more than those on other hosts (P < 0.05). The intrinsic rate of natural increase (r(m)) for D. citri on grapefruit was highest. Jackknife estimates of r(m) varied from 0.188 on grapefruit to 0.162 on orange jessamine and rough lemon. The mean population generation time on these hosts ranged from 31.6 to 34.1 d. The continuous flushes produced by orange jessamine could play an important role in maintaining high populations of this vector when the new flushes are not available in the commercial citrus groves.     

Effects of temperature on biology and life table parameters of the Asian citrus psyllid, Diaphorina citri Kuwayama (Homoptera: Psyllidae)

The development, survivorship, longevity, reproduction, and life table parameters of the Asian citrus psyllid, Diaphorina citri Kuwayama were evaluated at 10°C, 15°C, 20°C, 25°C, 28°C, 30°C and 33°C. The populations reared at 10°C and 33°C failed to develop. Between 15°C and 30°C, mean developmental period from egg to adult varied from 49.3 days at 15°C to 14.1 days at 28°C. The low‐temperature developmental thresholds for 1st through 5th instars were estimated at 11.7°C, 10.7°C, 10.1°C, 10.5°C and 10.9°C, respectively. A modified Logan model was used to describe the relationship between developmental rate and temperature. The survival of the 3rd through 5th nymphal instars at 15–28°C was essentially the same. The mean longevity of females increased with decreasing temperature within 15–30°C. The maximal longevity of individual females was recorded 117, 60, 56, 52 and 51 days at 15°C, 20°C, 25°C, 28°C and 30°C, respectively. The average number of eggs produced per female significantly increased with increasing temperature and reached a maximum of 748.3 eggs at 28°C (P<0.001). The population reared at 28°C had the highest intrinsic rate of increased (0.199) and net reproductive rate (292.2); and the shortest population doubling time (3.5 days) and mean generation time (28.6 days) compared with populations reared at 15–25°C. The optimum range of temperatures for D. citri population growth was 25–28°C.     

Identification by suppression subtractive hybridization of genes expressed in pear (Pyrus spp.) upon infestation with Cacopsylla pyri (Homoptera: Psyllidae)

The molecular interaction between pear tree (Pyrus spp.) and the phloem-feeding psylla Cacopsylla pyri (Linnaeus) was investigated through the construction and characterization of cDNA subtracted libraries. Genes expressed upon insect infestation were identified in the susceptible pear cultivar Bartlett and in the resistant selection NY10355. In both interactions, genes involved in the plant defense response were induced, confirming the observed similarity between the response to pathogens and to insects with piercing/sucking mouthparts. However, the two expression profiles were found to be different, with more genes involved in the response to biotic and abiotic stress being activated in the resistant plant than in the susceptible one. Further characterization of the identified genes could lead to the development of molecular markers associated with tolerance/resistance to pear psylla.     

Transmission of apple proliferation phytoplasma by Cacopsylla melanoneura (Homoptera: Psyllidae)

Transmission trials of apple proliferation (AP) phytoplasma to healthy apple plants were carried out with Cacopsylla melanoneura (Forster). Both field naturally infected and experimentally infected psyllids were evaluated. The capacity of the different life stages of the insect in transmitting AP was tested. Overwintered adults collected in the orchards were able to transmit AP with a variable efficiency, depending on the infectivity rate of source plants. Experimentally infected nymphs and springtime adults succeeded in the transmission of AP, but the lower number of insect tested and the shorter inoculation period, due to difficulties in rearing the whole cycle of the insect in the laboratory, affected the efficiency. Considering the life history of C. melanoneura, the overwintered adults are the most responsible of the diffusion of AP in apple orchards.     

Effect of sucrose octanoate on survival of nymphal and adult Diaphorina citri (Homoptera: Psyllidae)

Asian citrus psylla, Diaphorina citri Kuwayama (Homoptera: Psyllidae) was detected for the first time in the United States near Delray Beach, FL, on 2 June 1998 and is continuing to spread and multiply throughout southern Florida. This psyllid is the vector of Liberobacter asiaticum, a phloem-limited bacterium that causes citrus greening disease. This pathogen has not been found in the Western Hemisphere to date. Furthermore, high infestation levels of D. citri can impact citrus plant health, fruit quality, or yield. Replicated laboratory and spray booth bioassays were conducted to determine the insecticidal activity of a synthetic analog of natural sugar esters found in leaf trichomes of wild tobacco, Nicotiatna gossei Domin, to nymphal and adult D. citri. Field trials were initiated in Fort Pierce, FL, in 2000 to determine activity of the sugar ester formulation (sucrose octanoate) on D. citri and other citrus pests, including immature Asian citrus leafminer, Phyllocnistis citrella Stainton and mites. Sucrose octanoate rates tested ranged from 400 to 8000 ppm (0.1-2% formulated product). Our data suggest that both nymphal and adult D. citri as well as the mite complex tested would be equally controlled to levels of >90% at the higher concentrations of sucrose octanoate and that good coverage is key to efficacy.     

The influence of the host plant on the population dynamics of Acizzia russellae (Homoptera: Psyllidae)

Abstract. 1. The role of the host plant, Acacia karroo , in the population dynamics of the indigenous non-pest psyllid, Acizzia russellae , was investigated.
2. Population levels of A.russellae in early summer were almost 10 times greater on the regenerative foliage of pruned trees (cut back in spring) than on normal trees. During late summer and winter, populations declined far more slowly on pruned trees, so that very much higher numbers of psyllids were maintained on these trees through to the next spring. This finding, and others, suggest that natural enemies and climate are not major determinants in the population dynamics of this insect under normal conditions in the field.
3. Laboratory measurements of several chemical and physical characteristics of the foliage of pruned and normal trees did not reveal any differences which would account for the observed effects.
4. Measurements of organic nitrogen concentrations in the leaves of normal A. karroo trees in the field showed significant correlations between psyllid numbers and leaf nitrogen, but only during summer in November and January.
5. Psyllid performance in the laboratory (duration of life cycle, egg production, and dry weight of emergent females) was significantly better for psyllids reared on plants containing high amino nitrogen.
6. It is suggested that the availability of quantities of suitably high quality nutrients in the leaves of pruned A. karroo trees explains the "epidemic" population levels achieved by the psyllid on pruned plants. It seems that characteristics of the host plant impose the major limitation on psyllid population growth, which may explain the permanent low endemic population levels of this insect in the field.     

The mechanism of stylet movement in Psylla malt Schmidberger (Homoptera:Psyllidae)

The stylet movements in protracting, retracting and non-progressing stylet bundles of fifth stage nymphs of Psylla mali are described, together with observations on the role of the labium.     

NEW SPECIES OF PSYLLTDAE FROM SHAANXI PROV., CHINA(Homoptera: Psyllidae)

The present paper deals with 12 new species of psyllidae that belong to 3 gen-era from Shaanxi Prov. China. All the type specimens are separately deposited inthe Insect Collections of Beijing Agricultural University and Northwestern Agricultu-ral University.     

Host plant effects on the development and survivorship of the galling insect Neopelma baccharidis (Homoptera: Psyllidae)

In this study, the mortality factors acting upon the galling psyllid Neopelma baccharidis Burckhardt (Homoptera) caused by its host plant, Baccharis dracunculifolia De Candole (Asteraceae) were analysed. In March 1999, 982 galls of the same cohort were randomly marked on 109 individuals of B. dracunculifolia in the field. Galls were censused each month during their development, from April to August, and dead galls were collected and analysed for mortality factors. Gall dehiscence rates were calculated for each month. The major mortality source of N. baccharidis was gall dropping (13.2% of the original cohort), which is probably a normal outcome of previous mortality caused by the other factors observed in this study. Unknown factors killed 11.7% of this gall population and were ascribed to plant resistance during gall development. Empty galls represented 7.7% of the observed mortality and may be a consequence of egg retention or egg mortality/abortion related to variations in plant quality. Shoot mortality was high during the dry season and killed 7.5% of the galls, but this impact was minimized after the third month from gall formation due to the ability of nymphs to accelerate development and emerge from galls on dying shoots. However, the size of dehisced galls on dead shoots tended to be smaller, possibly affecting adult performance. Mortality of N. baccharidis attributed to B. dracunculifolia strongly controlled the galling insect population, killing 40.7% of the original cohort of galls. Plant‐mediated mortality was caused by often neglected factors acting predominantly during the first 3 months of development, which are critical to gall survivorship. These results reinforce the importance of bottom‐up forces in plant‐insect systems.     

First record of the Australian psyllid Ctenarytaina spatulata Taylor (Homoptera: Psyllidae) in Europe

Abstract: The Australian species Ctenarytaina spatulata Taylor (Homoptera: Psyllidae) is reported from Europe for the first time. In August of 2002, it was recorded in several eucalyptus plantations in central Portugal. During August and September of 2002, the insect was apparently circumscribed to the area between rivers Douro and Tagus, being absent in the North and South of the country. In February of 2003, C. spatulata was already present all over the country and also in every place we inspected in Spain, namely in Galicia, Extremadura and Andalucia regions. The dispersion of the insect suggests that its introduction in Iberian forests is recent. At the moment, damages were observed in plantations located in northern and central Portugal, and also in the north of Spain. Predation on C. spatulata by spiders, green lacewings (Neuroptera, Chrysopidae), hoverflies (Diptera, Syrphidae, Syrphinae), ladybeetles (Coleoptera, Coccinellidae), and minute pirate bugs (Hemiptera, Anthocoridae) was observed in the field.