Seasonal activity of Trechnites insidiosus (Hymenoptera: Encyrtidae) and its host Cacopsylla pyricola (Hemiptera: Psyllidae) in pear

Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae) is the most expensive and challenging insect pest of commercial pear trees in the Pacific Northwest. Integrated pest management (IPM) programs are working toward relying more heavily on natural enemies to reduce insecticide use. Trechnites insidiosus (Crawford) (Hymenoptera: Encyrtidae) is the main parasitoid of C. pyricola, but little is known about its biology in the region. Developing sampling tools is important for the deployment of IPM programs, including monitoring of natural enemies. In this study, we examined 2 conventional monitoring methods: beat trays and yellow sticky cards, in addition to screened sticky cards and 3D-printed cylinder traps. Additionally, we tested an overwintering trap for the collection of parasitized C. pyricola. The trapping methods were tested in orchards in Oregon and Washington. Unscreened cards caught the most T. insidiosus and C. pyricola, followed by screened cards, cylinder traps, and then beat trays. Beat trays sometimes failed to catch any T. insidiosus, even when it was found in abundance via other methods. Screened cards and cylinder traps reduced bycatch and increased ease of identifying T. insidiosus. Specimens from the cylinder traps were also more suitable for use in molecular analysis. The overwintering traps were effective at capturing parasitized C. pyricola, but were highly variable year to year. The ideal trapping method will vary based on research needs (e.g., DNA preservation, reducing bycatch, catching higher numbers), but both screened sticky cards and cylinder traps were viable methods for monitoring T. insidiosus and its host.

Turning a Pest into a Natural Enemy: Removing Earwigs from Stone Fruit and Releasing Them in Pome Fruit Enhances Pest Control

The European earwig Forficula auricularia (L.) (Dermaptera: Forficulidae) is an omnivorous insect that is considered a minor pest of stone fruit and a key predator of pests in pome fruit orchards. In many pome fruit orchards, earwigs are absent or in low abundance due to broad-spectrum spray programs and the slow recolonization rate of earwigs. Orchards in transition to organic or "selective" conventional programs often struggle to achieve effective levels of biological control, and thus, may benefit from inoculating earwigs to expedite their re-establishment. In a two-year study, we evaluated the potential for mass trapping earwigs from stone fruit using rolled cardboard traps to reduce fruit damage and provide earwigs for augmentation in pome fruit. We also tested whether a single mass release or five releases (on alternating weeks) of the same total number of earwigs in apples and pears reduced pests relative to plots where no releases occurred. Mass trapping did not decrease earwig abundance or substantially reduce fruit damage in stone fruit orchards. However, trapping was an efficient method for providing earwigs for augmentation. Earwig abundances were only increased in orchards where earwigs were previously low or absent; however, multiple orchards with varying prior levels of earwigs exhibited reductions in key pests (woolly apple aphid and pear psylla). For some other pests evaluated, plots with mass releases of earwigs had a slight trend in overall lower pest density when compared with control plots. A strategy for moving earwigs out of stone fruit orchards and into pome fruit orchards could be an effective method for augmenting orchard predator populations.

Pear psylla and natural enemy thresholds for successful integrated pest management in pears

Pear psylla, Cacopsylla pyricola (Förster), is the most economically challenging pest of commercial pears in Washington and Oregon, the top producers of pears in the United States. The objective of this study was to quantify economic injury levels and thresholds for pear psylla. We used the relationship between pear psylla adult and nymph densities, and fruit downgraded due to psylla honeydew marking to identify injury levels. We calculated economic injury levels using the cost of downgraded fruit and average management costs (spray materials and labor). Using economic injury levels, we determined economic thresholds for pear psylla, which include predicted pest population growth, natural enemy predation, and anticipated delays between when pest populations are measured and when managers apply interventions. Economic thresholds generated by this study were 0.1-0.3 second-generation nymphs per leaf and 0.2-0.8 third-generation nymphs per leaf depending on predicted price and yield for insecticide applications at 1,300 pear psylla degree days in the second generation and 2,600 pear psylla degree days in the third generation. Natural enemy inaction thresholds identified by this study were 6 Deraeocoris brevis or 3 Campylomma verbasci immatures per 30 trays or 2 earwigs per trap for third-generation optional insecticide applications.

Integrated Pest Management Programs for Pear Psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), Using Kaolin Clay and Reflective Plastic Mulch

Pear psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), is the most economically important pest of pears grown in Washington State. Standard conventional management programs involve season-long broad-spectrum insecticide sprays. Although the industry uses some tools that are not disruptive to biological control, such as kaolin clay and selective insecticides, they are additions to broad-spectrum insecticides instead of replacements. Conventional sprays suppress pear psylla through the spring and early summer; however, disruption of biological control leads to pear psylla outbreaks near harvest. In 2018 and 2019, we tested two season-long programs that used only selective approaches. The programs began with either kaolin clay or reflective plastic mulch and were followed by identical spray programs using only selective insecticides. Programs were compared with an industry standard conventional program that used numerous broad-spectrum insecticides throughout the season, and a check program with no insecticides for pear psylla. Experiments were conducted using replicated 40-tree plots in a research orchard near Wenatchee, WA with high pear psylla pressure. In both years, selective programs had similar pear psylla densities to the industry standard program and all had lower pear psylla densities and fruit injury than the check. Both selective programs had lower fruit injury than the industry standard in the first year, and similar injury to the industry standard in the second year. Our results suggest kaolin clay and reflective mulch can effectively suppress pear psylla populations and injury in the early season and support season-long selective management programs without the use of broad-spectrum insecticides.

Synthesis of the enantiomers of 13-methylheptacosane, the sex pheromone of pear psylla, Cacopsylla pyricola

An efficient and gram-scale enantioselective synthesis of (R)- and (S)-13-methylheptacosane, the sex pheromone of pear psylla, has been developed. The key steps of the approach included Evans' chiral auxiliaries and Wittig coupling of chiral phosphonium salt with aldehyde.

Management of Pear Psylla (Hemiptera: Psyllidae) Using Reflective Plastic Mulch

Pear psylla, Cacopsylla pyricola (Förster), has remained the most challenging pest of commercial pears in Washington and Oregon, the top producers of pears in the United States. The lack of effective integrated pest management tactics for this pest has been a major barrier to effective management. In this study, we examined the potential for reflective plastic mulch affixed beneath pear trees to suppress pear psylla. In 2017 and 2018, single pear tree (cv. Bartlett) plots of reflective plastic mulch, black plastic mulch, and no mulch (check) were established in a research orchard to compare their effects on pear psylla. Arthropods were sampled every 7-14 d from March through late summer. In both years, reflective mulch plots had significantly fewer pear psylla adults, eggs, and nymphs of the first generation compared with black plastic and check plots. However, later generations of psylla were not suppressed by reflective mulch. Semi-field tests were conducted in 2019 and 2020 using uniformly pruned potted pear trees on either reflective plastic mulch or grass to determine whether summerform adults were tolerant to reflected light from mulch, or if shading from vegetative growth negated the effect of the mulch. In both years, significantly fewer summerform adults and eggs were found in reflective mulch plots, suggesting that shading, rather than summerform tolerance, reduced effects from reflective mulch in the summer. This study demonstrates the potential for reflective mulch to suppress pear psylla and justifies future examination as part of a season-long management program.

The Artificial Sweetener, Erythritol, Has Insecticidal Properties Against Pear Psylla (Hemiptera: Psyllidae)

Erythritol is a dietary sweetener that is used for low-calorie or diabetic diets. Although safe for human consumption, erythritol is lethal to certain Dipteran pests, but insecticidal effects of erythritol on phloem-feeding insects have yet to be examined. Our goal was to determine whether erythritol has insecticidal activity against pear psylla, Cacopsylla pyricola (Foerster) (Hemiptera: Psyllidae). We first demonstrated that ingestion of erythritol solutions compared with water by pear psylla caused reduced feeding, impaired motor functions, and reduced survival time of adults. We then tested whether foliar treatment of pear leaves with erythritol was also lethal to pear psylla. Foliar treatment of erythritol led to reduced 3-d survival of pear psylla nymphs and adults, and reduced rates of oviposition by pear psylla adults. Psylla adults also preferred to settle on untreated leaves than on erythritol-treated leaves in preference assays. Finally, we conducted field experiments to test whether applications of erythritol provided pear trees with protection against pear psylla under natural field conditions. Those experiments showed a reduction in pear psylla nymphs on erythritol-treated trees compared with untreated trees, but only if the erythritol was completely dissolved into solution by heating. Laboratory trials confirmed the importance of heating. Results of our experiments demonstrate that erythritol is insecticidal to pear psylla nymphs and adults and provide the first report that erythritol is lethal to a phloem-feeding insect. These findings suggest that erythritol may provide a new safe and effective tool for the management of pear psylla.

Organic Control of Pear Psylla in Pear with Trunk Injection

Simple Summary

Organic pear production is challenged, in part, by short lived effects of biopesticides when applied as foliar sprays. Trunk injection may enhance their performance by delivering the biopesticides directly to the vascular system of the tree, right where pear psylla feed. The objective of this study is to compare trunk injections to foliar sprayed applications of two insecticides, azadirachtin and abamectin, on their ability to control pear psylla in pear trees. The azadirachtin and abamectin trunk injected treatments performed equally or better than two foliar applications in the control of the pear psylla. The trunk injected trees from the first season provided a moderate level of control into the second season, one year after the injections. This study suggests that trunk injection is a superior delivery system for biopesticides used in organic pear production.

Abstract

Organic production of pears is challenging in part because OMRI (Organic Materials Review Institute) approved biopesticides are short lived when applied as foliar sprays. Trunk injection is an alternative method of insecticide delivery that may enhance the performance of biopesticides for control of pear psylla. The objective of this study is to compare the efficacy of azadirachtin and abamectin in the control of pear psylla using two different application methods, airblast sprayer and trunk injection. Trunk injections of azadirachtin and abamectin were compared to airblast applications of equal labeled rates on 33-year-old Bartlett Pear trees (Pyrus communis L., var “Bartlett”). The azadirachtin and abamectin trunk injected treatments performed equally or better than the two airblast applications in the control of the pear psylla. The trunk injected trees from the first season provided a moderate level of control into the second season, one year after the injections. This study suggests that trunk injection is a superior delivery system for biopesticides used in organic pear production.

Host and Non-host 'Whistle Stops' for Psyllids: Molecular Gut Content Analysis by High-Throughput Sequencing Reveals Landscape-Level Movements of Psylloidea (Hemiptera)

Psyllids (Hemiptera: Psylloidea) are phloem-feeding insects that tend to be highly specific in their host plants. Some species are well-known agricultural pests, often as vectors of plant pathogens. Many pest psyllids colonize agricultural fields from non-crop reproductive hosts or from non-host transitory and winter shelter plants. Uncertainty about which non-crop species serve as sources of psyllids hinders efforts to predict which fields or orchards are at greater risk of being colonized by psyllids. High-throughput sequencing of trnL, trnF, and ITS was used to examine the dietary histories of three pest and two non-pest psyllid species encompassing a diversity of lifecycles: Cacopsylla pyricola (Förster) (Psyllidae), Bactericera cockerelli (Šulc) (Triozidae), Diaphorina citri Kuwayama (Liviidae), Aphalara loca Caldwell (Aphalaridae), and a Cacopsylla species complex associated with Salix (Malphighiales: Salicaceae). Results revealed an unexpectedly high level of feeding on non-host species by all five psyllid species. The identification of the dietary history of the psyllids allowed us to infer their landscape-scale movements prior to capture. Our study demonstrates a novel use for gut content analysis-to provide insight into landscape-scale movements of psyllids-thus providing a means to pinpoint the non-crop sources of pest psyllids colonizing agricultural crops. We observed previously unknown psyllid behaviors during our efforts to develop this method and discuss new research directions for the study of psyllid ecology.

Laboratory Screening of 26 Essential Oils Against Cacopsylla chinensis (Hemiptera: Psyllidae) and Field Confirmation of the Top Performer, Perilla frutescens (Lamiales: Lamiaceae)

Similar to other pear psylla species in Europe and America, Cacopsylla chinensis (Yang and Li) is one of the most important pests that causes yield loss in commercial pear orchards in China. To investigate effective essential oils as alternatives to conventional pesticides against C. chinensis, 26 essential oils derived from commonly used Chinese spices and medicinal herbs were screened for insecticidal activity. Among these, the essential oil from Perilla frutescens (L.) Britton leaves was the top performer; it exhibited strong and acute toxicity against pear psylla, with an LD50 value of 0.63 μg per adult. Then, we tested the constituents of the essential oil and its toxicity in the field. Field trials showed a 72% corrected reduction in the first-second-instar population 7 d after spraying P. frutescens leaf oil solution at a concentration of 1 mg/ml and a 47% corrected reduction at days 3 and 14. This report is the first to document the application of essential oil from P. frutescens leaves to control C. chinensis under field conditions. Our results suggest that P. frutescens oil can be considered a novel potential pesticide for C. chinensis control in pear orchards.

Grafting on resistant interstocks reduces scion susceptibility to pear psylla, Cacopsylla bidens

BACKGROUND

Pear psylla is a major obstacle to efficient integrated pest management in pear orchards in Israel and around the world. We used two accessions with natural resistance to pear psylla Cacopsylla bidens (Šulc) - Py.760-261 (760) and Py.701-202 (701), both apparently of Pyrus communis L. origin - as interstock grafts to confer psylla resistance to the commercially important 'Spadona Estiva' (Pyrus communis) scion (Spadona) cultivar. The interaction of the interstocks with quince (Cydonia oblong Mill.) and Pyrus betulifolia Bunge rootstocks was also tested.

RESULTS

Usage of Py.760-261 (760) and Py.701-202 (701) as interstocks for the psylla-sensitive Spadona resulted in a five-fold decrease in the C. bidens population, apparently as a consequence of antibiosis affecting nymph survival. Additionally, psylla survival was negatively correlated with the interstock length and amount of foliage. The yield and fruit quality of Spadona grafted on the '701' interstock equaled or even exceeded those of the control in fruit quantity, fruit size and soluble solids content, especially on P. betulifolia rootstock.

CONCLUSION

Susceptibility to pear psylla decreased significantly following grafting of commercial Spadona on resistant interstock. This is the first demonstration of increased resistance to pear psylla conferred by the use of resistant interstock in pear trees and among the few examples demonstrating transfer of resistance to insects from the interstock in fruit trees. © 2017 Society of Chemical Industry.

Stability of Cacopsylla pyricola (Hemiptera: Psyllidae) Populations in Pacific Northwest Pear Orchards Managed with Long-Term Mating Disruption for Cydia pomonella (Lepidoptera: Tortricidae)

This study focused on conservation biological control of pear psylla, Cacopsylla pyricola, in the Pacific Northwest, USA. We hypothesized that insecticides applied against the primary insect pest, codling moth Cydia pomonella, negatively impact natural enemies of pear psylla, thus causing outbreaks of this secondary pest. Hence, the objective of this study was to understand how codling moth management influences the abundance of pear psylla and its natural enemy complex in pear orchards managed under long-term codling moth mating disruption programs. We conducted this study within a pear orchard that had previously been under seasonal mating disruption for codling moth for eight years. We replicated two treatments, “natural enemy disrupt” (application of two combination sprays of spinetoram plus chlorantraniliprole timed against first-generation codling moth) and “natural enemy non-disrupt” four times in the orchard. Field sampling of psylla and natural enemies (i.e., lacewings, coccinellids, spiders, Campylomma verbasci, syrphid flies, earwigs) revealed that pear psylla populations remained well below treatment thresholds all season despite the reduced abundance of key pear psylla natural enemies in the natural enemy disrupt plots compared with the non-disrupt treatment. We speculate that pear psylla are difficult to disrupt when pear orchards are under long-term codling moth disruption.

Polyphenolic Profile of Pear Leaves with Different Resistance to Pear Psylla (Cacopsylla pyri)

The European pear psylla, Cacopsylla pyri L. (Hemiptera: Psyllidae), is one of the most serious arthropod pests of pear. Since proper control of this pest is essential, better understanding of the complex plant-pest relationship is mandatory. This research deals with constitutive polyphenolic profiles in leaves of 22 pear cultivars of diverse origin (P. communis, P. pyrifolia, and P. pyrifolia × P. communis) and different resistance to psylla. The study was designed to show which differences in the polyphenolic profile of leaves from resistant and susceptible pear cultivars could be utilized as information in subsequent breeding programs. The results demonstrated that the leaves of Oriental pear cultivars contained much higher amounts of p-hydroxybenzoic acid, ferulic acid, aesculin, and naringin, that, together with detected 3-O-(6″-O-p-coumaroyl)-hexoside, apigenin, apigenin 7-O-rutinoside, and hispidulin, indicated a clear difference between the species and might represent phenolics responsible for psylla resistance.

Insecticidal Potential of Clove Essential Oil and Its Constituents on Cacopsylla chinensis (Hemiptera: Psyllidae) in Laboratory and Field

Cacopsylla chinensis (Yang and Li) (Hemiptera: Psyllidae) is an important pest of pear in China. As an alternative to conventional chemical pesticides, botanicals including essential oils and their constituents could provide an eco-friendly and nonhazardous control method. In this study, the essential oil of clove buds (Syzygium aromaticum) was obtained by hydrodistillation. Five constituents, accounting for 99.89% of the oil, were identified by gas chromatography-mass spectrometry, and the major constituents were eugenol (88.61%) and eugenol acetate (8.89%), followed by β-caryophyllene (1.89%). In a laboratory bioassay, clove essential oil, commercial eugenol (99.00%) and β-caryophyllene (98.00%) exhibited strong contact toxicity against the summerform adults of C. chinensis with LD50 values of 0.730, 0.673, and 0.708 µg/adult, and against the nymphs with LD50 values of 1.795, 1.668, and 1.770 µg/nymph, respectively. In contrast, commercial eugenol acetate (98%) had LD50 values of 9.266 µg/adult and 9.942 µg/nymph. In a field trial, clove essential oil caused significant population reductions of 73.01% (4.80 mg/ml), 66.18% (2.40 mg/ml) and 46.56% (1.20 mg/ml), respectively. Our results demonstrated that clove essential oil and its constituents have potential as a source of natural insecticides.

Field evaluation of an entomopathogenic fungus, Metarhizium brunneum strain F52, against pear psylla, Cacopsylla pyri

BACKGROUND

The pear psylla, Cacopsylla pyri L. (Hemiptera: Psyllidae), is one of the most serious insect pests of pears in Turkey. In recent years, psyllid management has become increasingly difficult because of the development of insecticide resistance and the withdrawal of registered chemicals from the market. In this study, the field efficacy of an emulsifiable concentrate formulation of the entomopathogenic fungus, Metarhizium brunneum Petch strain F52 (Hypocreales: Clavicipitaceae), containing 5.5 × 10(9) conidia mL(-1) , was evaluated against C. pyri in south-western Turkey (Antalya) in two consecutive years, 2010 and 2011.

RESULTS

The results showed that the F52 product at 100 mL 100 L(-1) water reduced the number of psyllid eggs and young nymphs (first and second instars), causing up to 79 and 88% mortality, respectively, 7 days after treatment in the first year, and 72 and 82% mortality in the second year. However, it was less active against the older nymphs (third to fifth instars ) and achieved only up to 51% mortality 7 days after treatment in the first year, and 48% mortality in the second year.

CONCLUSION

The results suggest that the M. brunneum strain F52 product can be used as an alternative to conventional chemicals in controlling C. pyri early in the season.

Two pear accessions evaluated for susceptibility to pear psylla Cacopsylla bidens (Šulc) in Israel

BACKGROUND

The pear psylla, Cacopsylla bidens (Šulc), is one of the most damaging pests of commercial pear orchards in Israel. Psylla control is a major obstacle to efficient integrated pest management, necessitating research on cultivars with natural resistance to pear psylla. Recently, two pear accessions (Py.760-261 and Py.701-202) from the local Newe Ya'ar fruit tree live collection were identified as having apparent resistance to pear psylla. Our goal was to evaluate the resistance of these two accessions relative to the commercial cultivar Spadona Estiva, and to identify whether the resistance mechanisms in the former interfere with insect colonisation of the plant (antixenosis) or inhibit insect growth, development, reproduction and survival (antibiosis).

RESULTS

Settlement and development of C. bidens was evaluated under natural conditions (pear orchard), semi-natural conditions (potted plants), and on detached branches and leaves (laboratory). Our results indicate that the selection Py.760-261 is 10 times more resistant than Spadona while Py.701-202 is five times more resistant.

CONCLUSIONS

The resistance mechanism in both accessions appears to be antibiosis affecting nymph survival. These resistant accessions may be used as rootstock or as a source of resistant genes in breeding programmes.