INVASIVENESS OF AN EXOTIC GALL WASP IS INFLUENCED BY INTERACTIONS WITH EXOTIC AND ENDEMIC ORGANISMS

American chestnut was once a crucial component of North American forests, but it was functionally eliminated by the introduction of the chestnut blight fungus. Chestnut is recently experiencing resurgence, but the introduced Asian chestnut gall wasp, a specialist herbivore, threatens chestnut recovery. I characterized this invasion and the interactions developing with host associates as the gall wasp spread in North America. Gall wasp dispersal is attributable to host plant distribution, effects of prevailing winds during adult insect emergence, and to topography. This knowledge may be useful to more accurately predict locations of future gall wasp infestations. Gall wasp invasiveness is also affected by its ability to modulate reproduction and reallocate nutritive resources for body maintenance and egg quality. The gall wasp can form galls of different shape and structure based on population levels and parasitism pressure, in order to optimize fitness. Simple, uni-lobed galls are formed when population pressure is low, and complex, multi-lobed galls are formed when gall wasp populations are high. A fungal plant pathogen, identified as Colletotrichum sp., infects galls and acts as an opportunistic entomopathogen, causing gall wasp mortality while sparing the parasitoid. A non-native torymid parasitic wasp has been deployed for biological control. Using a Y-olfactometer I demonstrated that a combination of olfactory and visual cues from chestnut galls and chestnut foliage is required for parasitoid adults to locate hosts. In addition, I evaluated interactions between the gall wasp and stem cankers on chestnut. Using potted Chinese chestnut seedlings with or without gall wasp or a native Nectria cankering pathogen, I found that the gall wasp has a negative impact on plant fitness, and a positive impact on fungal fitness. My work helps elucidate ecological mechanisms underlying the success of the exotic Asian chestnut gall wasp in North America, and adds to our knowledge base characterizing evolving ecological interactions between native and introduced species

Phytoplasma Infection of a Tropical Root Crop Triggers Bottom-Up Cascades by Favoring Generalist Over Specialist Herbivores

Global interest on plant-microbe-insect interactions is rapidly growing, revealing the multiple ways in which microorganisms mediate plant-herbivore interactions. Phytopathogens regularly alter whole repertoires of plant phenotypic traits, and bring about shifts in key chemical or morphological characteristics of plant hosts. Pathogens can also cause cascading effects on higher trophic levels, and eventually shape entire plant-associated arthropod communities. We tested the hypothesis that a Candidatus Phytoplasma causing cassava witches’ broom (CWB) on cassava (Manihot esculenta Grantz) is altering species composition of invasive herbivores and their associated parasitic hymenopterans. We conducted observational studies in cassava fields in eastern Cambodia to assess the effect of CWB infection on abundance of specialist and generalist mealybugs (Homoptera: Pseudococcidae), and associated primary and hyper-parasitoid species. CWB infection positively affects overall mealybug abundance and species richness at a plant- and field-level, and disproportionately favors a generalist mealybug over a specialist feeder. CWB phytoplasma infection led to increased parasitoid richness and diversity, with richness of ‘comparative’ specialist taxa being the most significantly affected. Parasitism rate did not differ among infected and uninfected plants, and mealybug host suppression was not impacted. CWB phytoplasma modifies host plant quality for sap-feeding homopterans, differentially affects success rates of two invasive species, and generates niche opportunities for higher trophic orders. By doing so, a Candidatus phytoplasma affects broader food web structure and functioning, and assumes the role of an ecosystem engineer. Our work unveils key facets of phytoplasma ecology, and sheds light upon complex multi-trophic interactions mediated by an emerging phytopathogen. These findings have further implications for invasion ecology and management

Soil fertility regulates invasive herbivore performance and top-down control in tropical agroecosystems of Southeast Asia

In terrestrial ecosystems, changes in soil nutrient availability, plant growth or natural enemies can generate important shifts in abundance of organisms at various trophic levels. In agroecosystems the performance of (invasive) herbivores and their impacts on crops is of particular concern. Scientists are presently challenged with making reliable inferences on invader success, natural enemy performance and efficacy of biological control, particularly in tropical agroecosystems. In this study, we assess how trophic regulatory forces (bottom-up vs. top down) influence the success of three globally important pests of cassava. We examine the mealybug species (Hemiptera: Pseudococcidae) of differing host breadth and invasion history: Phenacoccus manihoti, Paracoccus marginatus, and Pseudococcus jackbeardsleyi. Potted plant fertilizer trials were combined with a regional survey in Vietnam, Laos and Cambodia of 65 cassava fields of similar size and age, but with varying soil fertility. Relative abundance of each mealybug invader was mapped along a soil fertility gradient, and contrasted with site-specific measures of parasitism. Potted plant trials revealed strong bottom-up effects for P. manihoti, such that impacts of nitrogen and potassium additions were propagated through to higher trophic levels and substantially boost development and fitness of its specialist parasitoid, Anagyrus lopezi (Hymenoptera: Encyrtidae). Field surveys indicate that mealybug performance is highly species-specific and context-dependent. For example, field-level abundance of P. jackbeardsleyi and P. marginatus, was related to measures of soil fertility parameters, soil texture and plant disease incidence. Furthermore, for P. manihoti, in-field abundance is equally associated with soil texture (i.e., silt content). Principal component analysis (PCA) and regression suggested that P. manihoti and P. marginatus are disproportionately favored in low-fertility conditions, while P. jackbeardsleyi prospers in settings with high organic carbon and phosphorus. Parasitism of P. manihoti by A. lopezi varied greatly with field and soil fertility conditions, and was highest in soils with intermediate fertility levels and where management practices include the addition of fertilizer supplements. Our characterization of the relative performance of invasive mealybugs and strength of parasitism across variable soil fertility conditions will help guide parasitoid release programs and soil management practices that enhance mealybug biological control

Crop pests and predators exhibit inconsistent responses to surrounding landscape composition

The idea that noncrop habitat enhances pest control and represents a win–win opportunity to conserve biodiversity and bolster yields has emerged as an agroecological paradigm. However, while noncrop habitat in landscapes surrounding farms sometimes benefits pest predators, natural enemy responses remain heterogeneous across studies and effects on pests are inconclusive. The observed heterogeneity in species responses to noncrop habitat may be biological in origin or could result from variation in how habitat and biocontrol are measured. Here, we use a pest-control database encompassing 132 studies and 6,759 sites worldwide to model natural enemy and pest abundances, predation rates, and crop damage as a function of landscape composition. Our results showed that although landscape composition explained significant variation within studies, pest and enemy abundances, predation rates, crop damage, and yields each exhibited different responses across studies, sometimes increasing and sometimes decreasing in landscapes with more noncrop habitat but overall showing no consistent trend. Thus, models that used landscape-composition variables to predict pest-control dynamics demonstrated little potential to explain variation across studies, though prediction did improve when comparing studies with similar crop and landscape features. Overall, our work shows that surrounding noncrop habitat does not consistently improve pest management, meaning habitat conservation may bolster production in some systems and depress yields in others. Future efforts to develop tools that inform farmers when habitat conservation truly represents a win–win would benefit from increased understanding of how landscape effects are modulated by local farm management and the biology of pests and their enemies

Symposium "Predicting new pest introductions: tools and strategies" - XXVI International Congress of Entomology (ICE)

Symposium presentation "Predicting new pest introductions: tools and strategies" for the XXVI International Congress of Entomology (ICE) held in Helsinki (Finland) on 18 July 2022.EU; en; PDF; [email protected]

Integrated management of arthropod pests of cassava: the case of Southeast Asia

High-yielding varieties and improved agronomy have led to substantial increases in cassava crop productivity throughout Southeast Asia; however, in recent years, those advances are being jeopardized by recurrent outbreaks of several non-native arthropod pests and (insect-vectored) pathogens. In this chapter, we provide an up-to-date account of recently-arrived invasive pests that are impacting Asia’s cassava crops and are having substantial repercussion for cassava crop production in multiple Asian countries. We indicate how both invasive insects, secondary pest outbreaks and insect-vectored diseases are becoming of increasing importance in several of Asia’s prime cassava-growing areas. We describe country-specific and regional mitigation programs and responses of local farmers to escalating pest outbreaks, listing both curative and preventative management tactics. We outline future opportunities for Integrated Pest Management (IPM) and arthropod biological control, and lay the basis for multi-disciplinary efforts to safeguard the long-term productivity, sustainability and agro-ecosystem health of one of Asia’s primary agricultural commodities. Table of contents 1 Introduction 2 Cassava pests in Southeast Asia 3 Guidelines for non-chemical pest management 4 Future trends and conclusion 5 Where to look for further information 6 Acknowledgements 7 Reference

EFSA activities on Pest Surveillance - EPPO Panels on Diagnostics in Virology, Mycology, Entomology, Bacteriology and Nematology

Presentations of EFSA activities on Pest Surveillance for EPPO Panels on Diagnostics in Virology (3 May), Mycology (7 September), Entomology (14 September), Bacteriology (11 October) and Nematology (8 November).EU; en; PDF; [email protected]

Surveillance of quarantine long-horned beetles in the EU - EC WG on Plant Health Surveillance 21 May 2021

Presentation of the surveillance of quarantine long-horned beetles in the EU - European Commission Working Group on Plant Health Surveillance on 21 May 2021.EU; PDF; [email protected]

Strumenti per la sorveglianza degli organismi nocivi: dalla preparazione alla progettazione - Regione Lombardia 5 Novembre 2020

Presentation of the Toolkit for plant pest surveillance during the training for phytosanitary inspectors organised by Regione Lombardia (NPPO).EU; PDF; [email protected]