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Background and Purpose: Dryocosmus kuriphilus is an invasive insect species of sweet chestnut (Castanea spp.) originating from China, and the only effective control measure against this pest is classical biological control with introduced parasitoid Torymus sinensis. This parasitoid has been widely released in many European countries, but it also has the ability to rapidly spread naturally. No official releases have been done in Bosnia and Herzegovina. Material and Methods: D. kuriphilus galls were collected in July 2017 on 6 localities in forest district Unsko (Una Sana canton) in Bosnia and Herzegovina. Presence and parasitism rates of T. sinensis were recorded in the entomological laboratory, Croatian Forest Research Institute. T. sinensis larvae were identified morphologically and by being compared with the voucher specimens. Results and Discussion: Torymus sinensis larvae were positively identified in the examined D. kuriphilus galls from all localities in Bosnia and Herzegovina. Parasitism rates ranged from 44.83 to 74%. Occurrence and high parasitism rates in Bosnia and Herzegovina observed in this study are not results of biocontrol releases of T. sinensis, but can be attributed to natural spread from Croatia. High parasitism rates observed in this study can indicate that the parasitoid was present in Bosnia and Herzegovina in 2016. Conclusions: This study presents the first record of Torymus sinensis in Bosnia and Herzegovina. We predict that the parasitoid will continue its spread over Bosnia and Herzegovina in sweet chestnut forests and orchards and that it will act as effective biological control agent against D. kuriphilus.

Citrus cultivation is characterized by high species richness and an abundance of pest insects and associated natural enemies. Since the successful introduction of Novius (= Rodolia) cardinalis into California in the late 19th century, which resulted in the world's first classical biological control (BC) program that targeted Icyerya purchasi , numerous classical BC programs have been initiated for the control of citrus pests, many of which have been very successful. The introduced and established new natural enemy species, together with the resident (both native and self-introduced), have enabled the development of conservation and augmentative BC programs in citrus. As a result, relatively few phytophagous species in citrus are considered key pests. However, this scenario has been disrupted by the spread of the lethal citrus disease, huanglongbing (HLB), caused by several bacteria of the genus Candidatus Liberibacter and vectored by psyllids, and by the higher arrival frequency of invasive pest species. Current management of HLB often requires broad-spectrum insecticide treatments to reduce vector densities to slow pathogen dissemination. Increased insecticide use in citrus disrupts BC and destabilizes Integrated Pest Management programs, which become more insecticide-intensive. The accelerating problem with invasive citrus pests is driven by increasing levels of international trade, tourism, and agriculture, as well as climate change. BC of these invasive pests in citrus is further complicated by increasing legal limitations imposed on the introduction of exotic natural enemies which further jeopardizes citrus farming in many citrus-producing regions. This special issue covers different aspects of BC programs against pests and diseases in several different citrus-growing regions. Work covered here also includes recent advances in BC postharvest citrus diseases and nematodes. [ABSTRACT FROM AUTHOR]

• The Asiatic parasitoids Spathius galinae and Tetrastichus planipennisi have been released in North America to manage emerald ash borer. • Yellow pan trap captures of Spathius galinae and Tetrastichus planipennisi varied among sites and years, and occurred across a wide range of growing degree days. • Placing yellow pan traps on trees with suppressed or intermediate crown classes, abundant epicormics sprouts and smaller diameters increased T. planipennisi capture rates. • Tetrastichus planipennisi yellow pan trap captures had a positive relationship with parasitized EAB larval densities from the previous year. Yellow pan traps are frequently used to monitor establishment of hymenopteran parasitoids introduced for biological control of the invasive ash pest, emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae). To evaluate and improve their efficacy as a monitoring tool, we conducted field studies during 2016–2019 in southern Michigan where the introduced hymenopteran larval parasitoids, Tetrastichus planipennisi Yang (Eulophidae) and Spathius galinae (Braconidae) Belokobylskij & Strazanac are established. Our objectives were to describe parasitoid seasonal abundance, identify host tree variables that might influence parasitoid capture numbers (i.e., number of adults captured) and capture rates (i.e., number of positive traps per collecting period), and compare parasitoid trap captures to parasitized EAB larval densities. Yellow pan trap capture numbers and rates of both species were low for most study sites and years. Captures of both parasitoid species occurred throughout the growing season and neither showed a consistent trend in seasonal abundance. Emerald ash borer infested trees with suppressed or intermediate crown classes had higher T. planipennisi capture numbers and rates than dominant or codominant crown classes. During some years, T. planipennisi capture rates increased with decreasing tree diameter at breast height (DBH) and T. planipennisi capture numbers increased with increasing numbers of epicormics sprouts on host trees. Spathius galinae captures had no significant relationship with host tree variables but low overall capture numbers, due to its more recent introduction, may have prevented detection of any relationships. Tetrastichus planipennisi adult capture numbers were positively related to previous year's densities of T. planipennisi parasitized larvae dissected from trees. Spathius galinae capture numbers were not correlated with parasitized EAB larval densities. We discuss the relevance of our findings to improve yellow pan trap efficacy for monitoring introduced EAB larval parasitoids. [ABSTRACT FROM AUTHOR]

ABSTRACT: The use of the parasitoid Neodusmetia sangwani to control the Rhodes grass mealybug Antonina graminis is one of the best examples of classical biological control in the world. The situation could not be different in Brazil, where the pest has also been introduced, and kept under control after the release of its natural enemy. In this review, it is united information with respect to the successful use of a natural enemy in this country. Notes about the description and biology of the insects involved and rearing and release procedures of the parasitoid for the Rhodes grass mealybug control in Brazil will also be presented.

Background and Purpose: Dryocosmus kuriphilus is a globally invasive insect pest, spreading very quickly in new habitats and making serious damage to sweet chestnut forests in Croatia and in several other European countries. Indigenous parasitoid species trophically associated with oak gallwasps have adapted to this new host but cannot effectively regulate its population density. Classical biological control using parasitoid Torymus sinensis has been proven to be the only effective method of controlling the populations of D. kuriphilus and has been successfully applied in Japan, South Korea, the USA and Italy. The aim of this review paper is to provide overview and up-to date knowledge about biological control of D. kurphilus and to describe first steps of introduction of T. sinensis to sweet chestnut forests in Croatia. Conclusions and Future Prospects: Results presented in this paper show adapted biology and behavioural traits of T. sinensis to its host D. kuriphilus. The history and results of introductions of T. sinensis to Japan, the USA, Italy, France and Hungary are shown. The first report of release of T. sinensis to sweet chestnut forests in Croatia is given with discussion on native parasitoids attacking D. kuriphilus. Possible negative effects of T. sinensis on native parasitoid fauna and risks that could influence the successful establishment of T. sinensis in Croatia are discussed. Previous experiences have shown that T. sinensis can successfully control the population density of D. kuriphilus, slowing down the spread and mitigating negative impact of this invasive chestnut pest and keeping the damage of D. kuriphilus at acceptable level. High specificity of T. sinensis suggests that it has limited potential of exploiting native hosts but further detailed monitoring of native parasitoid and possible interactions with introduced T. sinensis is strongly suggested.

The Asian citrus psyllid, Diaphorina citri , is a significant economic pest of citrus because it vectors a bacterium that causes the lethal citrus disease huanglongbing. From 2015 to 2016, digital video recorders were used to identify natural enemy species attacking sentinel immature D. citri colonies deployed monthly at three urban sites in southern California. Natural enemy activity during both daylight and nighttime hours was recorded. To examine the impact of ant-hemipteran mutualisms on biological control efficacy, we compared natural enemy interactions with D. citri colonies that were either fully exposed or protected from walking arthropods with a sticky barrier. Spiders (Aranae), syrphid larvae (Syrphidae), predatory mites (Phytoseiidae), green lacewing larvae (Chrysopidae), thrips (Thripidae), and the introduced parasitoid, Tamarixia radiata , were the dominant natural enemy groups visiting immature D. citri colonies over the course of the study. A significant proportion of syrphid and green lacewing larvae, and T. radiata visits to the sentinel colonies resulted in D. citri attacks. Spiders rarely attacked immature D. citri . Argentine ants, Linepithema humile , were the most common arthropod visiting D. citri colonies across all study sites and ants were active day and night. When ant access to D. citri colonies was restricted, natural enemy abundance and attack rates increased, particularly those by syrphids and T. radiata . This study highlights the importance of natural enemies and ant-psyllid interactions in the biological control of D. citri in urban citrus ecosystems. Therefore, conservation of natural enemies and ant control should be considered for the sustainable management of this pest-disease complex. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Classical biological control (CBC) is the introduction of a natural enemy of exotic origin to control a pest, usually also exotic, aiming at permanent control of the pest. CBC has been carried out widely over a variety of target organisms, but most commonly against insects, using parasitoids and predators and, occasionally, pathogens. Until 2010, 6158 introductions of parasitoids and predators were made against 588 insect pests, leading to the control of 172 pests. About 55% of these introductions were made against pests of woody plants. Establishment rates of natural enemies and success rates were higher in CBC projects targeting pests of woody plants than other pests. This review aims to answer the questions most commonly asked regarding CBC against insect pests, with particular emphasis on tree pests. The topics covered include, among others: variations in rates of successes among different systems, different target insect groups and different agents; temporal trends in CBC practices and successes; economic and environmental benefits; risks and ways to mitigate the risks; CBC against native pests; accidental successes through the adoption of the invasive pests by native natural enemies or accidentally introduced agents; and prospects and constraints for the practice of CBC in the future. Questions are answered based on the analysis of two databases, the BIOCAT2010 database of introductions of insect biological control agents for the CBC of insect pests, and a database of introductions of entomopathogens against insect pests. [ABSTRACT FROM AUTHOR]

We performed 'no-choice' tests to study the host range of the parasitoid Allotropa burrelli (Muesebeck) (Hymenoptera: Platygastridae) for use against the Comstock mealybug, Pseudococcus comstocki (Kuwana) (Hemiptera: Pseudococcidae), in Southern France. We tested three Pseudococcidae species as potential non-target hosts: two species from the same genus ( Pseudococcus longispinus and Pseudococcus viburni) and Planococcus citri. Allotropa burrelli did not parasitize any of the non-target mealybug species tested. No attempt of oviposition was recorded for the three species tested during the first 20 min of parasitoid release and no parasitism occurred in 6-8 hr of exposure of the mealybugs to the parasitoid. [ABSTRACT FROM AUTHOR]

The Asian citrus psyllid, Diaphorina citri Kuwayama ( Hemiptera: Liviidae), is a significant citrus pest and the parasitoid Tamarixia radiata ( Waterston) ( Hymenoptera: Eulophidae) has been released in various citrus-producing areas in classical biological control programs targeting D. citri. We investigated the effect of host deprivation on the foraging behavior and patch utilization by T. radiata. In the laboratory, females deprived of hosts for 3 days tended to leave patches of 12 nymphs without parasitizing hosts during the ca. 30 min they spent in the patch before leaving. Moreover, half of these females failed to host feed, and those that did host feed, on average, needed more than 15 min to complete feeding. Conversely, non-host-deprived females parasitized on average three nymphs before leaving patches without host feeding during the ca. 39 min they spent in the patch. These laboratory observations were compared to mass-reared female T. radiata that were released onto colonies of D. citri nymphs infesting citrus in the field. Release vials were provisioned with honey and these females had no opportunities to host feed over the 1- to 2-day containment period prior to release. When introduced onto D. citri colonies, 68% T. radiata females abandoned D. citri patches prior to probing hosts, in part, because Argentine ants, Linepithema humile ( Mayr) ( Hymenoptera: Formicidae), tending colonies disturbed searching parasitoids. These results from laboratory and field studies are discussed in the context of classical biological control, with the aim of understanding how to manipulate host availability and ant activity so establishment rates and impact of T. radiata can be improved. [ABSTRACT FROM AUTHOR]

The woodwasp Sirex noctilio is a devastating killer of pines in the southern hemisphere. Over the 20th Century, it has invaded exotic pine plantations in New Zealand, Australia, South America, and South Africa successively. In response to this woodwasp threat, in the 1960–70s CSIRO in Australia launched a major campaign of exploration for biological control agents in Europe, the Middle East, and North Africa, the presumed indigenous range of S. noctilio . The most promising natural enemy discovered was a nematode, Deladenus siricidicola , which lives inside a pine tree as a mycophagous form but becomes parasitic when near host larvae and sterilizes adult woodwasp females. Australian scientists developed a biological control management system based on the nematode, including how to rear and release it in the field. The CSIRO program has been a model for Sirex management in the pine-growing regions of the southern hemisphere since the 1960s. Thus, when S. noctilio was collected in North America in 2004, it seemed natural to try using the Australian model as a simple technology transfer. Unfortunately the transfer has not proved to be so simple. In the following, we present the results of six years of experimental controlled release studies, in which no nematodes were actually released into the field. One of the first discoveries was that another strain, a “non-sterilizing” strain, of D. siricidicola was already present in the areas invaded by S. noctilio . Our annual studies compared infection rates between trees inoculated with the Australian “Kamona strain” and controls without nematodes. In most cases, the treated trees had the higher rates of nematode parasitism, but the controls were not always zero, suggesting that the non-sterilizing strain was well-established in our study plots. Many of the Kamona-treated trees did not contain Kamonas, suggesting that the non-sterilizing strain may have out-competed the Kamonas. Even with Kamona treatments, there was relatively little sterilization, indeed much less than expected. It seems likely that the S. noctilio strain invading North America is physiologically different from the Australian nematode and not susceptible to Kamona sterilization. Another interesting result was observed between host tree species. In a three-year study, nematode parasitism rates were consistently higher in P. sylvestris than in P. resinosa and significantly higher when the three years of data were pooled. We conclude with the observation that the Kamona strain is apparently not compatible with the S. noctilio invading North America and suggest that more exploration is needed in its area of origin for different and more effective nematode genotypes. [ABSTRACT FROM AUTHOR]

Intra/interspecific predation byA. swirskii. Both Benin and Netherlands populations ofAmblyseius swirskiiengaged in cannibalism, and in predation onEuseius concordislarvae. Provision of pollen decreased cannibalism considerably, but had a smaller effect on predation onE. concordis. Potential effect of the eventual introduction ofA. swirskiifor control ofBemisia tabaciin Brazil is discussed. [ABSTRACT FROM AUTHOR]

The potential environmental risks of Neodryinus typhlocybae, a parasitic wasp from North America, were evaluated with regard to its safe use as an exotic biocontrol agent for the planthopper Metcalfa pruinosa in Austria. Following an earlier host range study of N. typhlocybae conducted in the laboratory, the present study assessed the potential for establishment and spread as well as negative indirect effects on non-target organisms. The potential release sites in Austria were analysed for matching of the climatic requirements for establishment of N. typhlocybae. The two proposed release locations, Vienna and Graz, have a predominantly similar climate to the parasitoid’s region of origin, though the comparably cooler mean summer temperatures might result in a low emergence rate of the partial second generation. The natural spread potential of N. typhlocybae was reviewed and is considered to be sufficiently good for released individuals to reach nearby sites infested with M. pruinosa. However, a perceptible spreading of N. typhlocybae females only occurs a few years after release and seems to be strongly dependent on the host density. Gelis areator, a hyperparasitoid of N. typhlocybae known to occur in Austria, might have negative effects on the population of the beneficial organism. Advantages and disadvantages of chemical and biological control methods against M. pruinosa were evaluated. It is concluded that N. typhlocybae is very well suited as a biological control agent for M. pruinosa in Austria, as no adverse effects on non-target species are expected but its release offers advantages with regard to sustainable and environmentally friendly pest management.