Specialist Natural Enemies Research Articles

Density dependence in forests is stronger in tropical and subtropical climates among closely related species

Density dependence has long been considered an important mechanism for species coexistence in forests. Density‐dependent processes can be important mechanisms driving differences in species diversity across latitudes. Here we examined the decline in strength of density dependence with increasing latitude, and particularly how density dependence affected both conspecifics and heterospecifics.Conspecific individuals within a species were predominantly aggregated at the three different latitudes of the three study sites in China. The percentage of aggregated species declined with increasing spatial scale and growth stages, which confirmed the overall importance of density dependence. Compared with a latitudinal gradient, the intensity of aggregation in the most northerly temperate (Changbaishan) plot was significantly higher than that in the tropical (Bawangling) or subtropical (Heishiding) plots. This showed that the strength of density dependence among conspecific individuals at low latitudes was stronger than that for high latitudes. We found that the more closely related species were more spatially adjacent in the temperate plot, while the opposite was true in the tropical and subtropical plots at most scales. After calculating the recruitment probability of all species of mature trees, we found that 19 of the 32 species in the tropical plot and 7 of the 12 species in the subtropical plot were less likely to recruit near closely related species. In the northern temperate plot, only one species demonstrated this phenomenon. These results therefore suggest that latitudinal variation in the intensity of negative density‐dependent recruitment resulting from specialist natural enemies (the Janzen–Connell hypothesis) may contribute to the latitudinal gradient of diversity in trees.The strength of density dependence at low latitudes was stronger than at high latitudes, regardless of whether this dependence was measured between only conspecific individuals or between individuals of closely related species.

Inadvertent biological control: an Australian thrips killing an invasive New Zealand tree in California

Transport hubs of international trade and tourism are sites of unprecedented long-distance dispersal of species and novel ecological interactions. In cases of invasive plants released from their specialist natural enemies, novel interactions with both resident enemies and new arrivals can accumulate and potentially reduce weed competitiveness. I present here one dramatic example of this, where an invasive woody weed in southern California is being rapidly controlled by an accidentally introduced genus-specialist herbivorous insect. The New Zealand native shrub/small tree, Myoporum laetum, is a long-time popular ornamental plant in California and has become an invasive woody weed. In 2005, a Myoporum-specific thrips, Klambothrips myopori, was discovered (and described) in California feeding on M. laetum leaves. Several searches have failed to find K. myopori in New Zealand and a population has recently been discovered in Tasmania, Australia, feeding on Myoporum insulare. In 5 years, K. myopori has killed off about half of southern Californian M. laetum with almost all surviving individuals being gradually defoliated. Inadequate border biosecurity has resulted in inadvertent biological control, in a rapid timeframe, caused by a novel enemy. Unfortunately, K. myopori has subsequently been accidentally transported from California to Hawaii where it is now killing off Hawaiian native Myoporum sandwicense. Transport hubs can both connect weeds with natural enemies and disperse those enemies more widely.

Induced plant defenses, host–pathogen interactions, and forest insect outbreaks

Cyclic outbreaks of defoliating insects devastate forests, but their causes are poorly understood. Outbreak cycles are often assumed to be driven by density-dependent mortality due to natural enemies, because pathogens and predators cause high mortality and because natural-enemy models reproduce fluctuations in defoliation data. The role of induced defenses is in contrast often dismissed, because toxic effects of defenses are often weak and because induced-defense models explain defoliation data no better than natural-enemy models. Natural-enemy models, however, fail to explain gypsy moth outbreaks in North America, in which outbreaks in forests with a higher percentage of oaks have alternated between severe and mild, whereas outbreaks in forests with a lower percentage of oaks have been uniformly moderate. Here we show that this pattern can be explained by an interaction between induced defenses and a natural enemy. We experimentally induced hydrolyzable-tannin defenses in red oak, to show that induction reduces variability in a gypsy moth's risk of baculovirus infection. Because this effect can modulate outbreak severity and because oaks are the only genus of gypsy moth host tree that can be induced, we extended a natural-enemy model to allow for spatial variability in inducibility. Our model shows alternating outbreaks in forests with a high frequency of oaks, and uniform outbreaks in forests with a low frequency of oaks, matching the data. The complexity of this effect suggests that detecting effects of induced defenses on defoliator cycles requires a combination of experiments and models.

Increased resistance towards generalist herbivory in the new range of a habitat‐forming seaweed

Interactions between plants and their biotic environment can drastically change during range‐expansion and result in rapid adaptive evolution of plant traits. According to the influential evolution of increased competitive ability (EICA) hypothesis escape from specialist natural enemies will lead to a reduction in defense levels, but the way in which generalist consumers in the new ranges affect the evolution of plant defenses remains poorly understood. We conducted a four month controlled environment experiment to examine if the high densities of the generalist herbivore Idotea baltica in the Baltic Sea have selected for increased grazer‐resistance in Fucus vesiculosus, a North Atlantic seaweed that has expanded into large parts of the brackish Baltic Sea. Genetic analysis using microsatellites showed that the sampled populations are genetically distinct, which strongly suggests that traits under divergent selection may readily diverge and populations evolve local adaptations. Feeding trials and measurements of defense metabolites, i.e., phlorotannins, showed that F. vesiculosus from the Baltic Sea was least preferred and contained more than 50% higher constitutive levels of phlorotannins than conspecifics in the North Sea (Skagerrak), while algae from the Öresund, one of the sounds connecting the Baltic Sea to the Skagerrak, had intermediate resistance levels both in terms of grazer preference and phlorotannin levels. These results suggest that the higher grazing pressure on F. vesiculosus expanded into the Baltic Sea has resulted in the evolution of increased resistance towards generalist grazing.

An entomophage park to promote natural enemy diversity

Undisturbed habitats of natural vegetation near agricultural areas protect and enhance specific natural enemies and provide them with resources such as nectar, pollen, physical refuge, alternative prey, alternative hosts and mating sites. In order to reduce the pesticide-induced mortality of natural enemies and to improve natural enemy fitness and effectiveness, one such area (termed an ‘entomophage park’) was established at the Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu, at Chatha, India in 2007. Naturally occurring plants, weeds, cultivated crops and flowers were monitored regularly for natural enemies. Seven sampling methods were employed to compare the abundance of natural enemies in the entomophage park and adjoining crop fields. Both entomophage diversity and abundance in the park were much higher than in the adjacent agricultural fields of vegetables and cereals. A total of 61 species of natural enemies were recovered from the entomophage park, as compared to 22 and 20 species in cereal and vegetable fields, respectively. The abundance of parasitoids (ichneumonids, braconids, scelionids and chalcidoids) was significantly higher in the park as compared to surveyed agricultural fields, as was egg parasitism by scelionids (Telenomus spp.) and trichogrammatids, and parasitisation by the larval parasitoid Campoletis chlorideae on Helicoverpa armigera. The entomophage park also significantly enhanced the fecundity and survival of the ichneumonid C. chlorideae, when compared to individuals collected from vegetable and cereal fields. Seventeen species of plants were recorded as ‘insectary plants' (one providing substantial floral resources) in the entomophage park. Such parks may play an important role in maintaining the biodiversity of natural enemies and enhancing natural pest control.

Testing for Phytochemical Synergism: Arthropod Community Responses to Induced Plant Volatile Blends Across Crops

Using herbivore-induced plant volatiles (HIPVs) to attract specific natural enemies in the field has proven challenging, partly because of a poor understanding of: (i) which compound(s) to manipulate to attract specific taxa, and (ii) the ecological conditions over which HIPVs are effective. To address these issues, we quantified the response of a complex arthropod community to three common HIPVs (methyl salicylate, cis-3-hexen-1-ol, and phenylethyl alcohol) as individual compounds and equal part blends in corn and soybean fields. Of 119 arthropod taxa surveyed, we found significant responses by four species in corn fields (2 parasitoids, 1 herbivore, and 1 detritivore) and 16 in soybean fields (8 parasitoids, 3 predators, 4 herbivores, and 1 detritivore), with both attractive and repellent effects of the HIPVs observed. For example, tachinid flies were highly attracted to cis-3-hexen-1-ol (ca. 3-fold increase), but repelled by methyl salicylate (ca. 60 % decrease). Surprisingly, we found very few cases in which HIPVs acted synergistically; only two arthropod groups (ichneumonid wasps and phorid flies) were more attracted by a blend of the HIPVs than by the individual compounds composing the blend. Crop type, however, had a strong impact on the strength of arthropod responses to HIPVs. A few arthropod species were broadly affected across both crops (i.e., the herbivore Halticus bractatus was repelled by most of our treatments, regardless of crop background), but overall more arthropod groups responded to HIPVs released in soybean fields compared with corn. This was true despite the fact that taxa responding to HIPVs were present and abundant in both systems, suggesting that crop-based outcomes were likely driven by the plant matrix rather than mere differences in taxonomic composition of the arthropod community in corn vs. soybean fields. As a whole, these results suggest that: (i) repellent effects of HIPVs on natural enemies of herbivorous insects can be observed as frequently as attractive effects; (ii) odor blends may be no more effective than single-compound lures for some taxa; and (iii) crop background alters the magnitude of attraction to HIPVs, depending on the species being targeted.

Australian family ties: does a lack of relatives help invasive plants escape natural enemies?

Invasive plants may initially be released from natural enemies when introduced to new regions, but once established, natural enemies may accumulate. How closely related invasive species are to species in the native recipient community may drive patterns of herbivore and pathogen damage and therefore, may be important in understanding the success of some invasions. We compared herbivore and pathogen damage across a group of invasive species occurring in natural environments on the east coast of Australia. We examined whether the level of damage experienced by the invasive species was associated with the degree of phylogenetic relatedness between these plants and the native plants within the region. We found that phylogenetic distance to the nearest native relative was a good predictor of herbivore and pathogen damage on the invasive plants, explaining nearly 37 % of the variance in leaf damage. Total leaf damage and the variety of damage types declined with increasing phylogenetic distance to the nearest native relative. In addition, as the phylogenetic distance to the nearest native relative increased, invasive species were colonized by fewer functional guilds and the herbivore assemblage was increasingly dominated by generalist species. These results suggest that invasive species that are only distantly related to those in the native invaded community may be released from specialist natural enemies. Our results indicate that the phylogenetic relatedness of invasive plants to species in native communities is a significant predictor of the rate of colonization by the herbivore and pathogen community, and thus a useful tool to assess invasion potential.

Biological control of aphids in the presence of thrips and their enemies

Generalist predators are often used in biological control programs, although they can be detrimental for pest control through interference with other natural enemies. Here, we assess the effects of generalist natural enemies on the control of two major pest species in sweet pepper: the green peach aphid Myzus persicae (Sulzer) and the western flower thrips Frankliniella occidentalis (Pergande). In greenhouses, two commonly used specialist natural enemies of aphids, the parasitoid Aphidius colemani Viereck and the predatory midge Aphidoletes aphidimyza (Rondani), were released together with either Neoseiulus cucumeris Oudemans, a predator of thrips and a hyperpredator of A. aphidimyza, or Orius majusculus (Reuter), a predator of thrips and aphids and intraguild predator of both specialist natural enemies. The combined use of O. majusculus, predatory midges and parasitoids clearly enhanced the suppression of aphids and consequently decreased the number of honeydew-contaminated fruits. Although intraguild predation by O. majusculus on predatory midges and parasitoids will have affected control of aphids negatively, this was apparently offset by the consumption of aphids by O. majusculus. In contrast, the hyperpredator N. cucumeris does not prey upon aphids, but seemed to release aphids from control by consuming eggs of the midge. Both N. cucumeris and O. majusculus did not affect rates of aphid parasitism by A. colemani. Thrips were also controlled effectively by O. majusculus. A laboratory experiment showed that adult predatory bugs feed on thrips as well as aphids and have no clear preference. Thus, the presence of thrips probably promoted the establishment of the predatory bugs and thereby the control of aphids. Our study shows that intraguild predation, which is potentially negative for biological control, may be more than compensated by positive effects of generalist predators, such as the control of multiple pests, and the establishment of natural enemies prior to pest invasions. Future work on biological control should focus on the impact of species interactions in communities of herbivorous arthropods and their enemies.

Biogeographical comparison of the invasive Lepidium draba in its native, expanded and introduced ranges

Invasive plants are expected to perform better and consequently be more abundant in their introduced compared to their native ranges. However, few studies have simultaneously compared plant and population traits along with biotic and abiotic environmental parameters for invasive and native plant populations. We compared 17 native Eastern European, 14 expanded Western European and 31 introduced US populations of the invasive Lepidium draba over 2 years. Most parameters were similar between the two European ranges, but differed for the US. Density, cover, and biomass of L. draba were greater in the US while cover of other vegetation was lower. Bare-ground and litter cover were greater for US populations in 1 year, as was L. draba shoot height and seed output. Availability of labile soil nitrogen was also greater in the US range. Endophagous shoot herbivory was greater in Western Europe compared to the US in 1 year. As expected, specialist herbivores were only found in Europe. Differences between ranges were not explained by varying environmental conditions (climate, altitude and latitude). In summary our results indicate that lower interspecific competition, higher resource availability and the lack of specialist natural enemies may all contribute to the increased performance of L. draba in its introduced US range. Additionally, L. draba is well adapted to disturbance events, which may further benefit its competitiveness at degraded sites. In general our results were consistent between years, which reinforces their validity. However, some of the differences were only significant in one of the 2 years, which, on the other hand, emphasizes the importance to ideally conduct biogeographic comparisons over multiple years.

Phenology and impact of natural enemies associated with the hop looper (Hypena humuli) in Washington State, USA

The hop looper, Hypena humuli Harris (Lepidoptera: Noctuidae), is becoming an increasingly important pest of hops (Humulus lupulus L.) (Rosales: Cannabaceae) in western USA. Currently, control of this pest usually involves broad-spectrum pesticides that kill natural enemies and disrupt biological control of other hop pests. In order to develop better management strategies for H. humuli, field and laboratory studies were conducted over a four-year period to identify the pest's natural enemies and to investigate their phenologies and to assess their impact. Nine parasitoid species and assorted species of invertebrate predator were found to attack different life-stages of H. humuli. Levels of parasitism were consistently low throughout the study period and none of the parasitoids found was a specialist natural enemy of the pests. Exclusion cage studies showed, however, that the complex of natural enemies as a whole can significantly reduce larval densities of the pest, and laboratory studies confirmed successful predation of H. humuli larvae by several generalist predators including the European earwig (Forficula auricularia L.), the damsel bug Nabis alternatus Parshley and two species of the geocorid bug genus Geocoris.

Biotic resistance via granivory: establishment by invasive, naturalized, and native asters reflects generalist preference

Escape from specialist natural enemies is frequently invoked to explain exotic plant invasions, but little attention has been paid to how generalist consumers in the recipient range may influence invasion. We examined how seed preferences of the widespread generalist granivore Peromyscus maniculatus related to recruitment of the strongly invasive exotic Centaurea stoebe and several weakly invasive exotics and natives by conducting laboratory feeding trials and seed addition experiments in the field. Laboratory feeding trials showed that P. maniculatus avoided consuming seeds of C. stoebe relative to the 12 other species tested, even when seeds of alternative species were 53-94% smaller than those of C. stoebe. Seed addition experiments conducted in and out of rodent exclosures revealed that weakly invasive exotics experienced relatively greater release from seed predation than C. stoebe, although this was not the case for natives. Seed mass explained 81% of the variation in recruitment associated with rodent exclusion for natives and weak invaders, with larger-seeded species benefiting most from protection from granivores. However, recruitment of C. stoebe was unaffected by rodent exclusion, even though the regression model predicted seeds of correspondingly large mass should experience substantial predation. These combined laboratory and field results suggest that generalist granivores can be an important biological filter in plant communities and that species-specific seed attributes that determine seed predation may help to explain variation in native plant recruitment and the success of exotic species invasions.

Can the enemy release hypothesis explain the success of invasive alien predators and parasitoids?

Biological invasions are ecologically and economically costly. Understanding the major mechanisms that contribute to an alien species becoming invasive is seen as essential for limiting the effects of invasive alien species. However, there are a number of fundamental questions that need addressing such as why some communities are more vulnerable to invasion than others and, indeed, why some alien species become widespread and abundant. The enemy release hypothesis (ERH) is widely evoked to explain the establishment and proliferation of an alien species. ERH predicts that an alien species introduced to a new region should experience a decrease in regulation by natural enemies which will lead to an increase in the distribution and abundance of the alien species. At the centre of this theory is the assumption that natural enemies are important regulators of populations. Additionally, the theory implies that such natural enemies have a stronger regulatory effect on native species than they do on alien species in the introduced range, and this disparity in enemy regulation results in increased population growth of the alien species. However, empirical evidence for the role of the ERH in invasion success is lacking, particularly for invertebrates. Many studies equate a reduction in the number of natural enemies associated with an alien species to release without studying population effects. Further insight is required in relation to the effects of specific natural enemies on alien and native species (particularly their ability to regulate populations). We review the role of ecological models in exploring ERH. We suggest that recent developments in molecular technologies offer considerable promise for investigating ERH in a community context.

Introduced pathogens follow the invasion front of a spreading alien host

1. When an invasive species first colonizes an area, there is an interval before any host-specific natural enemies arrive at the new location. Population densities of newly invading species are low, and the spatial and temporal interactions between spreading invasive species and specific natural enemies that follow are poorly understood. 2. We measured infection rates of two introduced host-specific pathogens, the entomophthoralean fungus Entomophaga maimaiga and the baculovirus Lymantria dispar nucleopolyhedrovirus (LdNPV), occurring in spreading populations of an invasive forest defoliator, L. dispar (gypsy moth), in central Wisconsin. 3. Over 3 years, we found that host density was closely associated with the presence and prevalence of both pathogens. The fungal and viral pathogens differed in the sensitivity of their response as E. maimaiga was present in lower-density host population than LdNPV. 4. We examined the relationship between weather conditions and infection prevalence and found that activity of both the fungus and virus was strongly seasonally influenced by temperature and rainfall or temperature alone, respectively. 5. Purposeful releases of pathogens (median distances of study sites from release sites were 65·2 km for E. maimaiga and 25·6 km for LdNPV) were not associated with pathogen prevalence. 6. A generalist fly parasitoid, Compsilura concinnata, also killed L. dispar larvae collected from the study sites, and parasitism was greater when infection by pathogens was lower. 7. Our results demonstrated that although infection levels were low in newly established host populations, host-specific pathogens had already moved into host populations close behind advancing populations of an invasive host; thus, spreading hosts were released from these enemies for only a relatively short time.

Do Induced Responses Mediate the Ecological Interactions Between the Specialist Herbivores and Phytopathogens of an Alpine Plant?

Plants are not passive victims of the myriad attackers that rely on them for nutrition. They have a suite of physical and chemical defences, and are even able to take advantage of the enemies of their enemies. These strategies are often only deployed upon attack, so may lead to indirect interactions between herbivores and phytopathogens. In this study we test for induced responses in wild populations of an alpine plant (Adenostyles alliariae) that possesses constitutive chemical defence (pyrrolizidine alkaloids) and specialist natural enemies (two species of leaf beetle, Oreina elongata and Oreina cacaliae, and the phytopathogenic rust Uromyces cacaliae). Plants were induced in the field using chemical elicitors of the jasmonic acid (JA) and salicylic acid (SA) pathways and monitored for one month under natural conditions. There was evidence for induced resistance, with lower probability and later incidence of attack by beetles in JA-induced plants and of rust infection in SA-induced plants. We also demonstrate ecological cross-effects, with reduced fungal attack following JA-induction, and a cost of SA-induction arising from increased beetle attack. As a result, there is the potential for negative indirect effects of the beetles on the rust, while in the field the positive indirect effect of the rust on the beetles appears to be over-ridden by direct effects on plant nutritional quality. Such interactions resulting from induced susceptibility and resistance must be considered if we are to exploit plant defences for crop protection using hormone elicitors or constitutive expression. More generally, the fact that induced defences are even found in species that possess constitutively-expressed chemical defence suggests that they may be ubiquitous in higher plants.

Intraguild predation in the presence of a shared natural enemy

Intraguild predation (IGP) is a widespread phenomenon in nature, and yet the simplest theoretical models of IGP predict that coexistence of intraguild predator and prey is only possible under restrictive assumptions. Here I examine how a specialist or generalist natural enemy of these species affects their long-term persistence and abundance, as functions of the natural enemy's relative attack severity and fecundity on each species. Notably, I show that failure to include the effects of a higher trophic level in models of IGP can lead to incorrect predictions about the coexistence or exclusion of guild members. I then consider how an interaction between native species and a natural enemy is perturbed by the arrival of an invasive intraguild predator. I outline the conditions under which the native species and/or its natural enemy are threatened by the arrival of the intraguild predator, and also when the natural enemy is beneficial in preventing the initial invasion or eventual dominance of the invader. This work provides new insights on the influence of omnivory on food web stability, and also generates testable hypotheses for predicting the impact of a novel intraguild predator on the recipient community at multiple trophic levels.

Organizmy pożyteczne w strategiach biologicznego zwalczania – grzyby owadobójcze

Fungal entomopathogens are widespread in nature and contribute to the natural regulation of insects. They can be exploited for pest management as biological control agents of pests in attempts to improve the sustainability of crop protection. Four types of biological control are recognized: classical, inoculation, inundation, and conservation biological control. Classical biological control is the intentional introduction and permanent establishment of an exotic biological agent for long-term pest management. Inoculation biological control is the intentional release of a living organism as a biological control agent with the expectation that it will multiply and control the pest for an extended period, but not permanently. Inundation biological control is the release of large numbers of mass-produced biological control agents to reduce a pest population without necessarily achieving continuing impact or establishment. Conservation biological control is a modification of the environment or existing practices to protect and enhance specific natural enemies or other organisms to reduce the effect of pests. The traditional and the most popular approach in biological control with entomopathogenic fungi has been to apply the fungal material to the cropping system (as biopesticide), using an inundation biological control strategy. The term biopesticide is used for microbial biological pest control agents that are applied in a similar manner to chemical pesticides. The use of biopesticides can substitute for some (but not all) chemicals and provide environmentally safe and sustainable control of pests but EU legislation and prohibitive registration costs are discouraging the development and commercialization of many promising new products.

Life tables for sunn pest,Eurygaster integriceps(Heteroptera: Scutelleridae) in northern Iran

Life table studies of sunn pest were carried out in Varamin, Iran, from 1998-2001 in order to determine stage-specific mortalities and the impact of specific natural enemies on population dynamics. Populations were sampled 2-3 times weekly in agricultural fields during the growing season and monthly during the period of dormancy at resting sites in nearby mountains some 30 km away from cereal fields. Adults spend a period of 9-10 months in diapause and suffered overcompensatory, density-dependent mortality during this period. Variation in adult overwintering survival was inferred to be largely a function of the physiological condition of bugs that is reduced in a density-dependent manner by intraspecific competition for food among newly molted adults prior to migration to resting sites. Adult mortality emerged as the primary factor in key factor analysis, contributing 73% of the total variance in mortality. Other important factors were egg parasitism by Trissolcus vassilievi Mayr and adult parasitism by several species of Tachinidae. Although T. vassilievi made only a minor contribution to overall variance in total mortality, it had a significant effect on the number of newly molted adults, the life stage that is most damaging to cereal crops. The equilibrium level of the pest population in wheat fields was inferred to be ca. 72.6 adults m(-2), a number that substantially exceeds the economic threshold that ranges from 3-5 adults m(-2).

Non-target effects of the ‘push–pull’ habitat management strategy: Parasitoid activity and soil fauna abundance

We assessed the non-target effects of a habitat management system (‘push–pull’) on maize stemborer specialist natural enemy activity and soil Collembola. Two study sites in western Kenya were sampled. There were two treatments at each site, maize monocrop and ‘push–pull’. The latter comprised an intercrop of maize and Desmodium, Desmodium uncinatum Jacq., with Napier grass, Pennisetum purpureum (Schumach), as a trap crop planted around the edge of the plot (spaced 1 m from main crop). Trichogramma spp. were recovered from stemborer eggs while Cotesia sesamiae and Cotesia flavipes were recovered from stemborer larvae, and Dentichasmias busseolae from pupae. Mean number of eggs parasitized was significantly higher in the maize monocrop than in the ‘push–pull’ plots however proportions parasitized did not differ between the two systems. The number of larvae and pupae parasitized and dead from causes other than parasitism similarly did not differ between cropping systems. Proportions of larvae and pupae parasitized were significantly higher in the ‘push–pull’ than in the monocrop plots, indicating that the activity of larval and pupal parasitoids was enhanced. C. sesamiae female wasps were attracted to the volatiles from Desmodium flowers but not those from the leaves in a four-arm olfactometer bioassay. A total of 1530 individual Collembola in seven families were recovered from the plots. The ‘push-pull’ strategy did not have any significant effect on Collembola abundance and dominance. The factors underlying these observations and their implications are discussed.

The Tenuipalpidae: an under-explored family of plant-feeding mites

The basic body structure of the Tenuipalpidae, or false spider, mites is discussed, along with morphological characters used for genus and species determination. The biology of these plant feeding mites is reviewed, including reproductive modes, dispersal and low chromosome number. The interactions of the false spider mites with their host plants and the damage they incur are considered, including the increasing economic importance of Brevipalpus spp. and of Raoiella indica Hirst. The associations of tenuipalpids with plant diseases, caused by bacteria, fungi and especially viruses, are discussed. Methods to reduce tenuipalpid damage are reviewed, including sampling and monitoring in the field, quarantine efforts and horticultural, chemical and biological control means. Lists of natural enemies are appended, and the scarcity of specific natural enemies of the Tenuipalpidae is noted. The postulated modes that these mites employ to elude their predators are discussed. Finally, suggestions for further research are outlined. These include exploration for false spider mites and their natural enemies in relatively little-surveyed regions, studies on the biology of additional pest species and on their toxins, studying the interactions between mites, hosts and plant diseases, and the various modes of sex determination and parthenogenesis in false spider mites, with emphasis on Brevipalpus spp. and their cryptic, possibly host-associated biotypes.

Mass Rearing of Pseudophilothrips ichini (Thysanoptera: Phlaeothripidae), an Approved Biological Control Agent for Brazilian Peppertree, Schinus terebinthifolius (Sapindales: Anacardiaceae)

Raddi, native to Argentina, Brazil, and Paraguay(Barkley 1944), is a non-native invasive weed inFlorida (Langeland & Burks 2008), California(Randall 2000), Hawaii (Hight et al. 2003), andTexas (Gonzalez & Christoffersen 2006). Thiswoody ornamental most likely was introducedinto Florida before 1900 (Morton 1978; Mack1991). It eventually escaped cultivation and is aserious problem in disturbed sites (e.g., fallowfarmlands, ditch banks), natural communitiessuch as pinelands, hardwood hammocks andmangrove forests, and the Everglades NationalPark (Toops 1979; Ewel et al. 1982).During the mid-1980s, Brazilian peppertreewas targeted for classical biological control inFlorida (Bennett et al. 1990; Habeck 1995). Thelong-term goal of this project is to introduce acomplex of specialist natural enemies into Floridathat are capable of selectively attacking and re-ducing the invasiveness of Brazilian peppertree.Surveys for natural enemies within the areas ofnatural distribution of Brazilian peppertree havebeen conducted, and biological and host rangestudies have been completed for several candi-date biological control agents (Cuda et al. 2006).In May 2007, the federal interagency TechnicalAdvisory Group for the Introduction of BiologicalControl Agents of Weeds (TAG) recommended therelease from quarantine of the stem-attackingthrips