Abstract
Drosophila suzukii, or spotted-wing drosophila, is now an established pest in many parts of the world, causing significant damage to numerous fruit crop industries. Native to East Asia, D. ...suzukii infestations started in the United States a decade ago, occupying a wide range of climates. To better understand invasion ecology of this pest, knowledge of past migration events, population structure, and genetic diversity is needed. In this study, we sequenced whole genomes of 237 individual flies collected across the continental United States, as well as several sites in Europe, Brazil, and Asia, to identify and analyze hundreds of thousands of genetic markers. We observed strong population structure between Western and Eastern US populations, but no evidence of any population structure between different latitudes within the continental United States, suggesting that there are no broad-scale adaptations occurring in response to differences in winter climates. We detect admixture from Hawaii to the Western United States and from the Eastern United States to Europe, in agreement with previously identified introduction routes inferred from microsatellite analysis. We also detect potential signals of admixture from the Western United States back to Asia, which could have important implications for shipping and quarantine policies for exported agriculture. We anticipate this large genomic dataset will spur future research into the genomic adaptations underlying D. suzukii pest activity and development of novel control methods for this agricultural pest.
The negative effects and duration of an immunomark (egg albumin) and fluorescent powder for marking phytoseiids were examined. Neither mark caused significant mortality, run-off, or reduction in ...fecundity. The fluorescent powder mark was more durable, but neither mark has sufficient durability to be used in a long-term mark-recapture study.
The seminal work of Stern and his coauthors on integrated control has had a profound and long-lasting effect on the development of IPM programs in western orchard systems. Management systems based ...solely on pesticides have proven to be unstable, and the success of IPM systems in western orchards has been driven by conservation of natural enemies to control secondary pests, combined with pesticides and mating disruption to suppress the key lepidopteran pests. However, the legislatively mandated changes in pesticide use patterns prompted by the Food Quality Protection Act of 1996 have resulted in an increased instability of pest populations in orchards because of natural enemy destruction. The management system changes have made it necessary to focus efforts on enhancing biological control not only of secondary pests but also of primary lepidopteran pests to help augment new pesticides and mating disruption tactics. The new management programs envisioned will be information extensive as well as time sensitive and will require redesign of educational and outreach programs to be successful. The developing programs will continue to use the core principles of Stern and his co-authors, but go beyond them to incorporate changes in society, technology and information transfer, as needed.
Tritrophic interactions may alter the efficacy of biocontrol agents such as Galendromus occidentalis, the primary predator of tetranychids in Washington State apple. Apple cultivars vary in leaf ...pubescence, which may differentially affect the performance of G. occidentalis.
The present study aimed to determine both preference and performance of G. occidentalis on pubescent and glabrous surfaces. Choice tests were conducted on two apple cultivars: ‘Oregon Spur Delicious’ – pubescent and ‘Golden Delicious’ – glabrous, as well as by adding simulated trichomes to a bean leaf disk. No‐choice tests measured oviposition and prey consumption on the two apple cultivars.
Galendromus occidentalis consumed more prey on the ‘Oregon Spur Delicious’ side of arenas, although only when arenas were constructed without including the leaf midrib. When the midrib was included, G. occidentalis preferred to oviposit on the ‘Oregon Spur Delicious’ side. The preference of G. occidentalis for simulated trichomes did not lead to a performance difference between cultivars. In the no‐choice test, G. occidentalis did not differ in performance between cultivars.
These studies indicate that G. occidentalis may have a slight preference for more pubescent surfaces, although this preference is not sufficiently strong to alter its biocontrol performance. As a specialist, G. occidentalis may be more adapted to tracking populations of its prey than locating ‘ideal’ host plants.
Tetranychus urticae Koch is a highly polyphagous pest that is notorious for developing resistance to pesticides. In many perennial cropping systems, integrated mite management relies on the ...conservation of natural enemies, especially phytoseiid mites, to prevent outbreaks. For successful conservation, it is important to understand non-target effects of pesticides on both spider mites and their key natural enemies, allowing producers to choose pesticides that do not selectively favor T. urticae over its natural enemies. Here, we examine lethal and sublethal non-target effects of common orchard insecticides and fungicides on T. urticae in laboratory assays and compare these effects to previous work with its most important predator in Washington orchards, Galendromus occidentalis (Nesbitt) (Phytoseiidae). In all cases, materials were either less harmful to T. urticae or were equally harmful to both species. Pesticides that were minimally harmful to T. urticae, but highly harmful to G. occidentalis included neonicotinoids (acetamiprid, thiacloprid, imidacloprid) and novaluron. The diamides (chlorantraniliprole, cyantraniliprole, flubendiamide) had minimal effect on both species. Some pesticides (lambda-cyhalothrin, spinetoram, spirotetramat) were highly toxic to both predator and prey. While the latter category may not cause immediate outbreaks, the ability of spider mites to develop resistance more quickly than their natural enemies indicates that these materials should be used with caution. This study emphasizes the importance of studying the non-target effects of pesticides on secondary pests and their biological control agents to provide a more detailed insight into conservation biological control.
•All pesticides were more toxic to Galendromus occidentalis than T. urticae.•Comparing toxicity allowed determination of potential to disrupt biocontrol.•Neonicotinoids and novaluron showed high potential to disrupt biocontrol.•Diamides are the least likely materials to disrupt mite biocontrol.•No materials caused hormologosis in Tetranychus urticae.
Insects often have facultative associations with bacterial endosymbionts, which can alter the insects' susceptibility to parasitism, pathogens, plant defenses, and certain classes of insecticides. We ...collected pear psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), from pear orchards in Washington and Oregon, and surveyed them for the presence of bacterial endosymbionts. Adult psyllids were collected on multiple dates to allow us to assay specimens of both the summer (summerform) and the overwintering (winterform) morphotypes. Two endosymbionts, Arsenophonus and Phytoplasma pyri, were detected in psyllids of both morphotypes in both states. A separate survey revealed similar associations present in psyllids collected in 1987. Arsenophonus was present in 80-100% of psyllids in all growing regions. A slightly lower proportion of summerform than winterform psyllids harbored the bacterium. Arsenophonus was present in the bacteriomes and developing oocytes of most psyllids, indicating that this endosymbiont is transovarially transmitted. This bacterium was also observed in the salivary glands and midguts of some psyllids. Phytoplasma pyri was present in a greater proportion of pear psylla from orchards near Yakima, WA, than from other regions, and was present in a higher proportion of winterforms than summerforms. We did not detect Wolbachia, Profftella, or Liberibacter europaeus, which are associated with other psyllid pests, including other species of Cacopsylla. Our study is the first to survey North American populations of C. pyricola for endosymbionts, and provides a foundation for further research on how bacterial associations may influence the ecology and management of this pest.
Fifteen pesticides were tested in laboratory bioassays on Galendromus occidentalis (Nesbitt), the principal phytoseiid mite predator in Washington apple orchards. We developed a rating system for ...pesticides using lethal and sublethal effects, and applied the rating system to our results. At the 1× dose, only spinetoram and lambda-cyhalothrin caused >75% acute mortality of females. Carbaryl, azinphos methyl, spinosad, spirotetramat, cyantraniliprole, and sulfur had relatively little effect on mortality, but moderate to high effects on fecundity. Egg viability was most affected by carbaryl, spinosad, novaluron, spirotetramat, and sulfur. Lambda-cyhalothrin, spinosad, and sulfur were the most toxic compounds to larvae. Materials such as sulfur and spinetoram had widely divergent toxicity to adults versus larvae. The cumulative impact of these effects was best integrated by the numbers of live larvae of the F1 generation. Using this measurement, spirotetramat, sulfur, spinetoram, acetamiprid, lambda-cyhalothrin, carbaryl and novaluron caused the greatest percentage reduction compared to the check, yet only spinetoram and lambda-cyhalothrin would have been identified as harmful in acute bioassays. These bioassays provide support for the benefits of measuring a range of sublethal effects and testing multiple life stages to provide an accurate assessment of the harmfulness of reduced-risk pesticides.
•We tested 15 pesticides used in apple for nontarget effects on predatory mites.•Many tests showed population effects not revealed in adult mortality bioassays.•The anthranilic diamides were found to be the least harmful to Galendromus occidentalis.•The majority of pesticides (60%) were rated as very harmful.
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•We highlight the overall accomplishments of the articles in this special issue.•Multi-tactic approaches that address key issues of biological control are needed for ...adoption.•Outreach success requires biological knowledge be delivered in multiple venues.
We embarked on a large project designed to help enhance biological control in apple, pear and walnut orchards in the western U.S., where management programs were in the midst of a transition from older organo-phosphate insecticides to mating disruption and newer reduced-risk insecticides. A “pesticide replacement therapy” approach resulted in unstable management programs with unpredictable outbreaks of spider mites and aphids. Our project was designed to provide growers and pest managers with information on the effects of newer pesticide chemistries on a suite of representative natural enemies in both the laboratory and field, potential of new monitoring tools using herbivore-induced plant volatiles and floral volatiles, phenology of the key natural enemy species, economic consequences of using an enhanced biological control program, and value of an outreach program to get project outcomes into the hands of decision-makers. We present an overview of both the successes and failures of the project and of new projects that have spun off from this project to further enhance biological control in our systems in the near future.
Phenacoccus aceris (Signoret, 1875), the apple mealybug, is a vector of little cherry virus 2 (LChV2), a causal pathogen of little cherry disease. Sweet cherry (Prunus avium Linnaeus) (Rosaceae) ...trees infected with LChV2 produce cherries of small size, poor color, and poor flavor, making the fruit unmarketable. Little cherry disease was first observed in British Columbia, Canada in 1933, where it had a dramatic impact on sweet cherry production, and was recently detected in Washington, U.S.A. cherry orchards. In 2014–2016, a natural infestation of P. aceris was monitored in an apple orchard located in Washington State University's Sunrise Orchard near Rock Island, Washington (47°18′45.14″N 120°04′08.31″W). Heavy parasitism was observed on overwintering nymphs and ovipositing female P. aceris, followed by a reduction in P. aceris crawlers. The emerged wasps were identified as the encyrtid Anagyrus schoenherri (Westwood, 1837). This is the first report of A. schoenherri parasitizing P. aceris in a Washington apple orchard, which represents an extension of the geographic distribution of A. schoenherri to the Nearctic Region. Reduction in P. aceris densities, one of the key vectors of LChV2, is potentially important for the sweet cherry industry in the Pacific Northwest. Historically, declining P. aceris populations in British Columbia were attributed to the establishment of a platygastrid parasitoid Allotropa utilisMuesebeck, 1939, suggesting that biological control could play a major role.
The effects of three sulfur products (calcium polysulfide = lime sulfur, dry flowable sulfur, and ammonium thiosulfate, a plant nutrient), were tested in bioassays against a predatory mite, ...Galandromus occidentalis (Nesbitt), and two species of tetranychid (pest) mites, twospotted spider mite (Tetranychus urticae Koch) and European red mite Panonychus ulmi (Koch). Calcium polysulfide and ammonium thiosulfate were acutely toxic on contact to adult females of all three mite species, causing 58–100% mortality in 48 h. Dry flowable sulfur, in contrast, was nontoxic to adults of all three species. Fresh residues of the sulfur products were essentially nontoxic to females of G. occidentalis and T. urticae. Galandromus occidentalis consumed 8.2 and 4.0× fewer prey contaminated with residues of calcium polysulfide and ammonium thiosulfate; dry flowable sulfur had no effect on prey consumption. Higher posttreatment temperatures (32 versus 18°C) did not affect the toxicity of dry flowable sulfur to G. occidentalis and T. urticae. The toxic effect of the sulfur products was not related to the concentration of elemental S but rather to some intrinsic characteristic of the compound itself. There were substantial differences in the responses of different stages of G. occidentalis. Residues that were nontoxic to adult females were highly toxic to hatching larvae, including those of dry flowable sulfur. In addition, all three products were highly repellent to adult female G. occidentalis. The lethal effect of calcium polysulfide on larvae was still present when the laboratory-aged residues onbean leaves were 8–9 d old. Field-aged residues on apple (Malus spp.) leaves were highly toxic (89% mortality) after 7 d, but mortality declined to 50 and 17% after 14 and 22 d, respectively. The increasing use of sulfur-containing products is detrimental to predatory mites and may play a role in the diminishing effectiveness of integrated mite control in Washington apple orchards.
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