Pear Psylla Research Articles

Jumping plant-louse Cacopsylla (Hepatopsella) bidens (Sulc, 1907) (Hemiptera, Psyllidae) new pest on pear in Serbia

The problem of jumping plant - lice, an important pest on pear, appeared in the middle of the twentieth century and represents a direct consequence of pear cultivation on large areas with intensive application of agrotechnical, pomotechnical and chemical protection measures. Three species of jumping plant - lice are known on pear in Serbia: Cacopsylla pyri, C. pyrisuga i C. pyricola, among which C. pyri is the most important pest in intensive orchards. During jumping plant - lice fauna research in Serbia, besides these three species, another one was determined as well - Cacopsylla bidens. In the period from 2005 to 2010, the presence and harmfulness of C. bidens were determined at 56 localities, both in intensive and extensive pear orchards. Besides on cultivated pears, C. bidens was also determined on wild species of Pyrus genus. In our conditions, C. bidens overwinters in adult stage on pear. The activation of the adults that have overwintered occurs at the beginning of March. The extended period of oviposition provides permanent presence of all developmental stages on plant, so the generations overlap. It can develop 3 to 4 generations per year. Since this is the first record of the species in Serbia, this paper describes basic morphological characteristics of the species, development cycle and distribution.

Hedgerow effects on the distribution of beneficial arthropods in a pear orchard in Southern France

Farming intensification in recent decades has led to an alarming level of degradation and loss of wildlife and its habitat such as hedgerows. The relationship between biodiversity and ecosystem functioning has emerged as a central issue in ecological sciences, but the impact of regarding hedgerow function as a potential source of biological control agents against agricultural pests remains poorly understood. In this paper, we assessed effects of the arthropod community in a neighbouring hedge on the distribution of the pest psylla, Cacopsylla pyri, in a pear orchard over three consecutive years (1999-2001). We measured the diversity of the arthropod community in the hedge and in the orchard at increasing distances from the hedge using Shannon index diversity. Other indices and statistics such the Hellinger and L1 distances were used to measure dissimilarities between spatial and temporal population distributions patterns. Our results showed in particular a decreasing diversity gradient as distance from the hedge increased and a convergence between predator populations in the orchard and the hedgerow during psylla proliferation. The beneficial arthropod exchanges occurring between the mixed hedgerow and the pear orchard during the pest proliferation period suggested that field border management could be used in an integrated pest management strategy aimed at reducing insecticide use.

Effect of host plant makeup through nitrogen fertilization and growth regulators on the pear psylla population

The pear psylla, Cacopsylla bidens (Sulc), is one of the most damaging pests of commercial pear orchards in Israel. However, growers today have only two pesticides left to control the pear psylla, therefore alternative control methods are needed. Our goal was to find ways to control the psylla population through rational use of cultural control methods: manipulating the levels of nitrogen fertilization, and using growth regulators. Our objectives were to determine the impact of nitrogen fertilization level on pear psylla populations, the impact of application of plant growth regulators (clormequat chloride and prohexadion-calcium) on psylla populations, and whether there is an interaction between the two factors in a semi-field-scale and in field-scale experiments. Higher oviposition and nymph development rates were found in trees that had higher leaf-nitrogen contents. Lower oviposition, nymph survival, and nymph development rates were found in trees that were treated with growth regulators. The suppress...

‘Candidatus Liberibacter europaeus’ sp. nov. that is associated with and transmitted by the psyllid Cacopsylla pyri apparently behaves as an endophyte rather than a pathogen

'Candidatus Liberibacter spp.' cause serious plant diseases. 'Candidatus Liberibacter asiaticus', 'Ca. L. americanus' and 'Ca. L. africanus' are the aetiological agents of citrus greening (Huanglongbing) in Asia, America and Africa. 'Candidatus Liberibacter solanacearum' causes diseases in Solanaceae in America and New Zealand. All four species are vectored by psyllid insects of different genera. Here, we show that the pear psyllid pest Cacopsylla pyri (L.) hosts a novel liberibacter species that we named 'Ca. Liberibacter europaeus'. It can bloom to high titres in the psyllid host, with more than 10(9) 16S rRNA gene copies per individual. Fluorescent in situ hybridization experiments showed that 'Ca. L. europaeus' is present in the host midgut lumen, salivary glands and Malpighian tubules. 'Candidatus L. europaeus' has a relatively high prevalence (> 51%) in C. pyri from different areas in the Piedmont and Valle d'Aosta regions in Italy and can be transmitted to pear plants in experimental transmission trials. However, even though high titres of the bacterium (more than 10(8) 16S rRNA gene copies g(-1) of pear plant tissue) could be detected, in the pear tissues no specific disease symptoms could be observed in the infected plants over a 6-month period. Despite liberibacters representing potential quarantine organisms, 'Ca. L. europaeus', first described in Italy and Europe, apparently behaves as an endophyte rather than a pathogen.

Survey of Susceptibility to Abamectin of Pear Psylla (Hemiptera: Psyllidae) in Northern Italy

The pear psylla, Cacopsylla pyri L. (Hemiptera: Psyllidae), is a relevant pest of pear, Pyrus communis L., trees in Emilia-Romagna region (northern Italy). The susceptibility to the insecticide abamectin was evaluated at different times of the year on C. pyri populations undergoing different control strategies within conventional, integrated, and organic farms. The tests performed were the egg spray and the topic and dip bioassay on adults. The larval mortality was evaluated by dip bioassay on treated leaves. The activity of P450-dependent monooxygenases, a relevant enzyme system involved in insecticide resistance of C. pyri, was also determined in adults by 7-ethoxycoumarin O-deethylation (ECOD assay). Tests on treated eggs and on larvae showed no significant differences in LC50 and LC90, although these values were always lower in individuals collected from organic farms in comparison with all other farms. Tests on overwintering adults revealed differences among populations, probably more related to collection time than to field pest control strategies. Unexpectedly, the ECOD assay on adults showed a slightly higher cytochrome P450 monooxygenase activity in the population undergoing organic control in comparison to others. Our results indicate that egg spray is the most reliable bioassay to verify data of open-field applications. Apparently, no resistance to abamectin has yet been developed by C. pyri in Emilia-Romagna.

Relative attractiveness of colour traps to pear psylla in relation to seasonal changes in pear phenology

AbstractMonitoring of pear psylla (Cacopsylla pyricola (Förster), Hemiptera: Psyllidae) prior to spring bud break could aid in predicting the size of subsequent spring populations and lead to improved proactive management decisions. Yellow traps are commonly used to monitor hemipteran pests including pear psylla, but very little is known regarding seasonal changes in attractiveness of yellow traps or relative attractiveness of colours other than yellow. This study presents seasonal colour-trap preferences of pear psyllas based on pear (Pyrus communis L., Rosaceae) phenological stages in the mid-Atlantic region of the United States of America. Black, blue, brown, clear (colourless), green, orange, red, white, and yellow traps were assayed against wild adult psylla populations over a 2-year period. Pear psyllas had a strong preference for yellow and orange when green leaves were present; however, we found no statistically significant difference between traps of different colours prior to spring bud break. Significantly more female psyllas were caught overall, but there was no gender-based colour bias. None of our colour traps caught significantly fewer psyllas than did clear (background hue) traps, suggesting that no traps were repellent.

Identification of a Sex Attractant Pheromone for Male Winterform Pear Psylla, Cacopsylla pyricola

Pear psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), a major economic pest of pears, uses a female-produced sex attractant pheromone. We compared the chemical profiles obtained from cuticular extracts of diapausing and post-diapause winterform males and females to isolate and identify the pheromone. Post-diapause females produced significantly more of the cuticular hydrocarbon, 13-methylheptacosane, than post-diapause males and diapausing females. In olfactometer assays, conspecific males were attracted to synthetic racemic 13-methylheptacosane, whereas females were not, indicating that the behavioral response to this chemical is sex-specific. Furthermore, 13-methylheptacosane was as attractive to males as a cuticular extract of females, suggesting that this chemical was largely responsible for the female attractiveness. A field study showed that males but not females were attracted to 13-methylheptacosane, confirming the olfactometer results. This study provides evidence that 13-methylheptacosane is a sex attractant pheromone for C. pyricola winterform males. This is the first identification of a sex pheromone in the Psylloidea. Our results open the path to developing monitoring tools and possibly new strategies for integrated pest management of this insect.

Impact of kaolin particle film, spirodiclofen acaricide, harpin protein, and an organic biostimulant on pear psylla Cacopsylla pyri (Hemiptera: Psyllidae)

Pear psylla Cacopsylla pyri (L.) is among the most serious pests in pear orchards. Field studies were conducted in 2005 and 2006 on pear trees (Pyrus communis L.) to assess the effect of kaolin-based particle film, spirodiclofen acaricide, harpin protein, and an organic biostimulant on C. pyri infestations. Pear psylla nymph densities were effectively suppressed over the entire season by kaolin particle film and spirodiclofen treatments compared with the untreated control. Harpin protein protected pear trees almost as well as the spirodiclofen acaricide, while the organic biostimulant provided no protection. Kaolin particle film, spirodiclofen, and harpin protein-sprayed pear trees significantly outperformed their unsprayed counterparts in terms of fruit load. Based on the results of this study, it seems that kaolin particle film, spirodiclofen, and harpin protein could be used as alternatives to broad-spectrum insecticides for suppressing pear psylla infestations.

Habitat and prey preferences of the two predatory bugs Anthocoris nemorum (L.) and A. nemoralis (Fabricius) (Anthocoridae: Hemiptera-Heteroptera)

The annual occurrence and distribution of the predatory bugs Anthocoris nemorum and Anthocoris nemoralis between apple, pear and herbal vegetation, was assessed in three apple orchards in 2001, and in two apple and two pear orchards in 2002. In the laboratory anthocorid prey preference was assessed in two-choice experiments with key pests of apple and pear including pear psyllid, apple psyllid, green apple aphid, rosy apple aphid and red spider mites. Anthocorid predation behavior towards pear psyllids was assessed. Anthocorids were the dominant early season predatory bugs. A. nemorum dominated in apple, while A. nemoralis dominated in pear. A. nemorum was also common in herbal vegetation, especially in mid-summer. Anthocorid numbers were correlated with numbers of collembola, psyllids and aphids in apple, and with numbers of psyllids in pear. A. nemoralis preferred pear psyllid to green apple aphid, while A. nemorum preferred green apple aphid . Both species preferred psyllids to spider mites. The success rate of A. nemoralis in attacking pear psyllids was higher than that of A. nemorum. A. nemorum had two generations in both 2001 and 2002 proving that it can be bivoltine under Danish climate conditions. The mid-summer move by A. nemorum from trees to herbal vegetation suggests that herbal vegetation may maintain A. nemorum in orchards at times of low prey numbers in the trees. Habitat and prey preference trials both identify A. nemorum as a biological control agent of special importance in apple, whereas A. nemoralis is of importance in pear.

Attraction ofCacopsylla pyricola(Hemiptera: Psyllidae) to Female Psylla in Pear Orchards

The pear psylla, Cacopsylla pyricola (Förster), is a major economic pest of pears in North America and Europe. Laboratory studies have shown that males of both the summerform and winterform morphotypes in this species are attracted to volatiles given off by females. This study tested whether attraction by males to females can be shown in the field. We showed that males had a clear preference for sticky traps that had been baited with live females compared with traps baited with live males or traps that were left unbaited. Female C. pyricola did not exhibit a preference among the three types of trap treatments. These results were obtained for both morphotypes. Trap catch was also monitored at 2-h intervals to assess whether capture of males on female-baited traps varied with time of day. Summerform male C. pyricola were caught in highest numbers between 1,445 and 1,645 hours, whereas winterform males were most often captured between 1,300 and 1,700 hours on traps baited with females. In both trials, there was again a significant preference by males for the female-baited traps compared with unbaited traps. Long-term practical benefits of the methods developed here provide a platform for the development of more effective monitoring tools, use in mating disruption, or development of lure and kill technologies.

Are populations of European earwigs, Forficula auricularia, density dependent?

AbstractBiocontrol using naturally occurring predators is often limited by population parameters of those predators. Earwigs, Forficula auricularia L. (Dermaptera: Forficulidae), are important predators in fruit orchards. They are capable of suppressing outbreaks of pest species, such as pear psyllid and various apple aphid species. Earwigs therefore play an important role in integrated pest management in fruit orchards and are essential in organic top fruit cultures. However, earwig populations are very unstable, showing large between‐year variation in densities, which limits their practical use. Extensive knowledge of regulating processes of populations is therefore crucial for efficient orchard management. A 2‐year phenological study in several apple and pear orchards in Belgium showed a significant displacement of third instars during the second brood in relation to the presence of adults. We also observed a yearly population crash at the time of moulting into adults. This population decrease was correlated with earwig numbers at peak density. The crash occurred at lower earwig densities in apple orchards than in pear orchards. Six possible regulating mechanisms for this density‐dependent decrease are discussed: (1) migration, (2) pesticides or orchard management, (3) starvation, (4) pathogens, (5) parasites and parasitoids, and (6) predation or cannibalism. If we can identify these regulating processes, specific management activities could be developed to prevent the population crash, hereby increasing population densities in the orchards.

Attraction of male winterform pear psylla to female‐produced volatiles and to female extracts and evidence of male–male repellency

AbstractPear psylla, Cacopsylla pyricola (Förster) (Homoptera: Psyllidae), is a major pest of commercial pears in North America and Europe. Olfactometer trials have shown that males of both the summer and winter morphotype are attracted to female‐infested host material. Additional work with the summer morphotype has shown that males are attracted to females even in the absence of the host plant, which is evidence that female C. pyricola produce a volatile sex attractant. Here, we describe similar results with the winterform, confirming for this morphotype that the female psylla rather than the infested host material is the source of the attractant. Male winterforms displayed attraction to odors from live females in the absence of the host plant, freshly killed females, and female whole body extracts. The female whole body extracts were at least as attractive as a comparable number of live females, suggesting that we were successful at extracting the components of the attractant with this procedure. All previous olfactometer trials with C. pyricola used the insect as the attractant source; the current study is the first to demonstrate that volatile chemicals isolated from the female insect were attractive to male conspecifics. Winterform males were also assayed to odors produced by conspecific males. We found that male psylla avoided volatile odors from live males, freshly killed males, or whole body extracts of males. To our knowledge, these results are the first indication that males of any member of the Psyllidae avoid odors associated with conspecific males.

Effectiveness of azadirachtin (NeemAzal-T/S) in controlling pear psylla (Cacopsylla pyri) and European red mite (Panonychus ulmi)

Here we present the results of field trials conducted in Serbia to evaluate the effectiveness of a neem-based product, NeemAzal-T/S (containing azadirachtin-A as its active ingredient in the form of an emulsifiable concentrate) against pear psylla (Cacopsylla pyri) and European red mite (Panonychus ulmi). Efficacy evaluation against C. pyri was carried out in a commercial pear orchard of the Williams pear cultivar, located at Borkovac (Ruma). The insecticides were applied at BBCH 09 pear growth stage, several days before the beginning of hatching of the first generation larvae. The efficacy of azadirachtin was compared to that of mineral oil, abamectin and diflubenzuron. Efficacy evaluation 18 DAT showed total termination of egg laying by C. pyri after treatments with azadirachtin and abamectin, while some new (white) eggs were found after treatment with mineral oil. Diflubenzuron treatment failed to fully stop egg laying, but the number of white eggs was significantly lower than it was in the control. Azadirachtin and abamectin achieved 100% efficacy, while the effectiveness of mineral oil was 97.4%, and that of diflubenzuron a mere 59%. All four insecticides significantly reduced the number of older (yellow) eggs and larvae, the efficacy being 80.5-92.6% (yellow eggs), 69.8-79.3% (larvae I-III instar) and 94.3-100% (larvae IV-V instar). In evaluation 38 DAT, azadirachtin, abamectin and mineral oil achieved 100% efficacy against white and yellow eggs, while diflubenzuron achieved 93% and 86.9% efficacy. All four insecticides were found to demonstrate high efficacy against I-III instar larvae (99.2-100%), but mineral oil treatment alone achieved high efficacy against IV-V instar larvae (92.4%) as well. Efficacy evaluation against P. ulmi was carried out in a commercial orchard of the Red Chief apple cultivar located at Morovic (Sid). Azadirachtin efficacy in controlling a summer population of European red mite was compared to a mineral oil, clofentezine and spirodiclofen. The acaricides were applied when the number of P. ulmi motile forms was below the orientational damage threshold of 3 motile forms per leaf. Azadirachtin reduced significantly the number of motile forms, leaving it well below damage threshold by the end of the trial. Good control efficacy was achieved (77.2-90.4%), the highest level of efficacy being recorded at the end of the trial 38 DAT. In mineral oil treatment 7 DAT, efficacy was 92.4%; 14 DAT and 21 DAT it was 75.2% and 78.9%, and it dropped to below 60% at the end of the trial. The efficacy of clofentezine (39.4-68.2%) was unsatisfactory, which is probably the result of a resistance developing under high selection pressure of these compounds in the Morovic locality in preceding years, while the newly introduced acaricide spirodiclofen showed high and long-lasting efficacy (97.2%, 38 DAT). The results of the trials are discussed in terms of improving management of the populations of European red mite and pear psylla.

Development of Monoclonal Antibodies to Pear Psylla (Hemiptera: Psyllidae) and Evaluation of Field Predation by Two Key Predators

The pear psylla, Cacopsylla pyricola (Forster) (Hemiptera: Psyllidae), and related psyllids are important pests of pear (Pyrus spp.) worldwide. Many of these pests are thought to be partially controlled by predatory insects. To improve our understanding of the predator species that attack pear psylla, we developed monoclonal antibodies (MAbs) against this pest for predator gut content studies. Mice were immunized with homogenates of nymphal, adult, and egg stages of pear psylla. A mouse immunized with nymph homogenate showed high activity against all three antigen types and was used for MAb development. From 952 hybridomas screened, 35 showed good activity to pear psylla and low activity against nontarget arthropods. Four MAbs were retained: two from immunoglobulin M (IgM)-secreting hybridomas, both with high activity against all stages of psylla except young eggs, and two immunoglobin G-secreting hybridomas, both with high activity against psylla eggs and gravid adult females. Using one of the IgM-MAbs, pear psylla remains were detected in the predatory bugs Anthocoris tomentosus Pericart (Heteroptera: Anthocoridae) and Deraeocoris brevis (Uhler) (Heteroptera: Miridae) in laboratory feeding trials. Digestion half lives typically exceeded 24 h and were dependent on meal size and predator life stage. Gut content analysis of 970 field-collected D. brevis and Anthocoris spp. showed that the proportion which fed on psylla averaged 59% and that percentage closely tracked the density of pear psylla nymphs during three seasons. The utility of these antibodies for the study of trophic interactions and habitat management in relation to biological control of pear psylla is discussed.

Development of Monoclonal Antibodies to Pear Psylla (Hemiptera: Psyllidae) and Evaluation of Field Predation by Two Key Predators

The pear psylla, Cacopsylla pyricola (Forster) (Hemiptera: Psyllidae), and related psyllids are important pests of pear (Pyrus spp.) worldwide. Many of these pests are thought to be partially controlled by predatory insects. To improve our understanding of the predator species that attack pear psylla, we developed monoclonal antibodies (MAbs) against this pest for predator gut content studies. Mice were immunized with homogenates of nymphal, adult, and egg stages of pear psylla. A mouse immunized with nymph homogenate showed high activity against all three antigen types and was used for MAb development. From 952 hybridomas screened, 35 showed good activity to pear psylla and low activity against nontarget arthropods. Four MAbs were retained: two from immunoglobulin M (IgM)-secreting hybridomas, both with high activity against all stages of psylla except young eggs, and two immunoglobin G-secreting hybridomas, both with high activity against psylla eggs and gravid adult females. Using one of the IgM-MAbs, pear psylla remains were detected in the predatory bugs Anthocoris tomentosus Pericart (Heteroptera: Anthocoridae) and Deraeocoris brevis (Uhler) (Heteroptera: Miridae) in laboratory feeding trials. Digestion half lives typically exceeded 24 h and were dependent on meal size and predator life stage. Gut content analysis of 970 field-collected D. brevis and Anthocoris spp. showed that the proportion which fed on psylla averaged 59% and that percentage closely tracked the density of pear psylla nymphs during three seasons. The utility of these antibodies for the study of trophic interactions and habitat management in relation to biological control of pear psylla is discussed.

Attraction of male summerform pear psylla to volatiles from female pear psylla: effects of female age, mating status, and presence of host plant

AbstractPear psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), is a pest of pears, Pyrus L. (Rosaceae), throughout North America and western Europe. Previous studies in our laboratory showed that males of the overwintering form (winter morphotype) were attracted to volatile chemicals from pear shoots infested with post-diapause females. The current study shows that males of the summer morphotype also are attracted to volatiles from female-infested host material. Older females (8–10 d old) were significantly more attractive to males than younger (2–5 d old) females. Both virgin and mated females attracted male psylla. Volatiles from female summerforms attracted males even in the absence of host-plant material, and both living and freshly killed females were attractive. Our results indicate that female C. pyricola emit a volatile sex attractant, and the results of the studies further define the life-history conditions in female pear psylla that lead to male attraction.

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.

배과원에서 꼬마배나무이 월동성충의 수상 이동시기 예측 모형

Pear psylla, Caccopsylla pyricola (Homoptera: Psyllidae), is a serious insect pest in pear orchards. C. pyricola overwinters as adults under rough bark scales of pear trees. When the weather warms up in the spring, the overwintered adults become active, climb up to the tree branches, and inhabit on fruit twigs to lay eggs. This study was conducted to develop a forecasting model for the onset of upward-movement of overwintered C. pyricola adults to control them by timely spraying of petroleum oil. The adult population densities were observed under rough barks (B) and on fruit twigs (T) of pear trees. Relative upward-movement rates (R) were calculated as T/(B+T). Low threshold temperatures for the activation of overwintered C. pyricola adults were selected arbitrarily from 5 to at a interval. Then, the days (D) when daily maximum air temperatures were above each low threshold temperature were counted from 1 February until to the dates with R 0.8. The same methods were applied for the prediction of the first observation of eggs. The variation of coefficients (CV) for the mean Des were lowest with the low threshold temperature of . At this selected threshold temperature, the upward movement of C. pyricola adults occurred with 12 D and they started laying eggs with 25 D. In the field validation, the model outputs with the threshold temperature reasonably well explained the observed data in Suwon and Cheonan in 2002. Practical usages of the model were also discussed.

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.

Preliminary Resistance Screening on Abamectin in Pear Psylla (Hemiptera: Psyllidae) in Northern Italy

Preliminary Resistance Screening on Abamectin in Pear Psylla (Hemiptera: Psyllidae) in Northern Italy