Review: predatory soil mites as biocontrol agents of above- and below-ground plant pests

Biological pest control is becoming increasingly important for sustainable agriculture. Although many species of natural enemies are already being used commercially, efficient biological control of various pests is still lacking, and there is a need for more biocontrol agents. In this review, we focus on predatory soil mites, their role as natural enemies, and their biocontrol potential, mainly in vegetable and ornamental crops, with an emphasis on greenhouse systems. These predators are still underrepresented in biological control, but have several advantages compared to predators living on above-ground plant parts. For example, predatory soil mites are often easy and affordable to mass rear, as most of them are generalist predators, which also means that they may be used against various pests and can survive periods of pest scarcity by feeding on alternative prey or food. Many of them can also endure unfavourable conditions, making it easier for them to establish in various crops. Based on the current literature, we show that they have potential to control a variety of pests, both in greenhouses and in the field. However, more research is needed to fully understand and appreciate their potential as biocontrol agents. We review and discuss several methods to increase their efficiency, such as supplying them with alternative food and changing soil/litter structure to enable persistence of their populations. We conclude that predatory soil mites deserve more attention in future studies to increase their application in agricultural crops.

     

Repeated visitations of spermatophores and polyandry in females of eriophyoid mites

Eriophyoid females store sperm either asymmetrically in one spermatheca, or symmetrically in both spermathecae. Previous studies have suggested that species in which females store sperm asymmetrically pick up sperm from only one spermatophore, while those with symmetrical sperm storage pick up sperm from two or more spermatophores during their lifetime. The aim of this study was to examine spermatophore visitation behaviour and symmetry of sperm storage in Aculops allotrichus from the black locust tree and Cecidophyopsis hendersoni from the yucca. This would indicate monandry or polyandry in these species. In both eriophyoids, the spermatophore visitation consisted of three phases: mounting, lying on the spermatophore and dismounting. Aculops allotrichus stored sperm asymmetrically. However, nearly one-third of the observed females visited two spermatophores, rather than only one in their lives. When A. allotrichus females visited two spermatophores they spent a similar amount of time at the first and at the second visitation. Also, the times of visitation of the first of the two spermatophores and the single spermatophore in a female lifetime did not differ significantly. This would suggest that apart from monandry, double insemination also occurs in this species. By contrast, C. hendersoni females were polyandrous. They stored sperm symmetrically and visited several spermatophores, on average 1.54 (max 6) per day, and up to 33 spermatophores in their lives. The benefits of repeated spermatophore visitation and the possible mechanisms of sperm storage in both species are discussed.     

Factors affecting the potential of phytoseiid mites (Acari: Phytoseiidae) as biocontrol agents in North-Italian vineyards

The results of a 5-year study on the relationships between spider mites and their predators in vineyards in Northern Italy are reported. The efficacy of the two predatory mites appeared to be strongly affected by various factors (grape variety, presence of macropredators, climatic condition, interspecific competition, phytoseiid strain). The phytoseiid mitesAmblyseius aberrans (Oud.) andTyphlodromus pyri Scheuten were released at three different density levels in two vineyards (A, B) infested byEotetranychus carpini (Oud.). One strain ofA. aberrans and two strains ofT. pyri were used for the experiments. In vineyard A,Panonychus ulmi (Koch) was recorded in the second and subsequent years of the experiments and became dominant overE. carpini from the third year onwards. The presence of anthocorids in the same vineyard increased the complexity of the system and gave us the possibility of comparing two very different situations. Release of low numbers ofA. aberrans gave a satisfactory control of spider mite populations in both vineyards. These results were even obtained on a variety non preferred by phytoseiids (Merlot) and with the continuous presence of anthocorids (vineyard A). After 5 years,A. aberrans was observed in 53% of the plots in vineyard A and in all plots of the other vineyard (B). Results of experiments in whichT. pyri was released were similar to those obtained in the experiments withA. aberrans, but only in the first year of the study. In vineyard A, theT. pyri populations declined dramatically from the second year onwards; the use of a non-preferred variety (Merlot) and the continuous presence of anthocorids seemed the most important factors causing the decline of predatory mite density. In vineyard B,T. pyri was capable of controlling spider mites even in the second year of the experiments. A very low density of macropredators and a preferred grape variety (Raboso) positively affected control. The density ofT. pyri in vineyard B decreased at the end of the second year because of adverse climatic conditions (high temperatures in combination with a low relative humidity). The decrease ofT. pyri allowed the displacement of this species byA. aberrans in all plots of vineyard B. It was also shown that the twoT. pyri strains differed in their efficacy to control spider mites. The research was partially supported by a grant from Regione Veneto (“Lotta biologica e integrata nel controllo di insetti ed acari dannosi”). The general lines of the research were planned by C. Duso and the most relevant part of the experiments was carried out by the same author. C. Pasqualetto contributed to the experimental work especially during 1989 and 1990.     

Genome sequences and characterization of the related Gordonia phages GTE5 and GRU1 and their use as potential biocontrol agents

Activated sludge plants suffer frequently from the operational problem of stable foam formation on aerobic reactor surfaces, which can be difficult to prevent. Many foams are stabilized by mycolic acid-containing Actinobacteria, the mycolata. The in situ biocontrol of foaming using phages is an attractive strategy. We describe two polyvalent phages, GTE5 and GRU1, targeting Gordonia terrae and Gordonia rubrupertincta, respectively, isolated from activated sludge. Phage GRU1 also propagates on Nocardia nova. Both phages belong to the family Siphoviridae and have similar-size icosahedral heads that encapsulate double-stranded DNA genomes (～65 kb). Their genome sequences are similar to each other but markedly different from those of other sequenced phages. Both are arranged in a modular fashion. These phages can reduce or eliminate foam formation by their host cells under laboratory conditions.     

Adventive eriophyoid mites: a global review of their impact, pathways, prevention and challenges

Eriophyoids have high potential as adventive mite species (AMS) because their small size make them difficult to detect, and can be easily distributed in world trade. Economic, social and environmental impact from adventive eriophyoid mites has been significant. Considerable attention has been given to adventive insect species while adventive mites have received little attention and little information is available for eriophyoids. This paper summarizes information on adventive eriophyoid mites, their impact, and the history of some important invasions. The status of adventive species of eriophyoids introduced as biological control agents of weeds is presented. A list of eriophyoid mites reported as invasive species worldwide is given. Pathways of concern and biosecurity actions to reduce the risk of eriophyoid mites are discussed. The need to raise public awareness of the risk and importance of these tiny organisms as AMS is emphasized. Scientific and technical challenges to deal with adventive eriophyoids are discussed.     

外来入侵杂草的生物防治及生防因子对本地非目标种的影响

随着生物入侵所引起的生态及经济问题日益严重,对有害入侵生物的防治问题也备受人们关注。生物防治因具有持续、高效、安全等优点,已成为防治有害入侵生物的重要方法。传统生防是防治有害入侵杂草的一种重要方法。在简单介绍生物防治的基础上,重点阐述了传统生物防治的理论基础——天敌逃逸假说,生防因子对外来人侵种的影响及其对本地非目标种的直接和间接效应,并针对这些问题,对我国开展生物防治工作提出几点建议。     

Oribatid mites: prospects for their use in ecotoxicology

Oribatid mites are a group of arthropods that have had remarkable evolutionary success with regard to species richness, variety of habitats colonized, life-cycle variation and reporductive patterns. The aim of this paper is to review some of the important features of Oribatida in relation to the possible use of these animals in ecotoxicological experiments. Their often sedentary way of living, combined with a narrow dependence on microhabitats qualify oribatids as potential indicator organisms for air and soil quality. Some species have been shown to be extremely sensitive to air pollutants such as SO₂ and NO₂. A low metabolic rate may be the driving force for slow development, low fertility, iteroparity and long adult life. Given these life-cycle characteristics, oribatids may be particularly vulnerable to intoxication by persistent contaminants. Work done on heavy metals suggests that the capacity for accumulation differs greatly between species. The camisiid Platynothrus peltifer accumulates high amounts of trace metals, specifically Mn. The toxicity of Cd, Cu and Pb has been studied in P. peltifer, demonstrating the necessity to consider egg production as a sensitive criterion. It is concluded that oribatid mites hold a great potential for use in ecotoxicology, due to the structural and functional complexity of their communities, and several peculiarities not found in other arthropods. The possibilities offered by this diverse group have not yet been fully employed by ecotoxicologists.     

The control of eriophyoid mites: state of the art and future challenges

The superfamily of the Eriophyoidea is a large and diverse group of mites, including a number of species of economic importance, mainly on perennial plants in agriculture and forestry. This review focuses on the economic importance and pest status of this group of mites, with emphasis on some genera. The available acaricide portfolio is reviewed and the influence of EU legislation policy on the sustainable control of Eriophyoidea is investigated. Possible generic guidelines for sustainable control and resistance management with special reference to the European situation are discussed. Recent advances in biological and integrated control of eriophyid mite pests and the implementation of these techniques in crops are explored. Furthermore, the relevance of studies on behaviour, epidemiology and diagnostics in general terms and as a strategic necessity is pointed out.     

Host-plant specialization by a non-herbivorous amphipod: advantages for the amphipod and costs for the seaweed

Studies of factors affecting host plant specialization by herbivores commonly highlight the value of the plant as both food and habitat, but often cannot distinguish the relative importance of these plant traits. A different approach is to study non-herbivorous animals that specialize on particular plants but do not feed on tissue from these plants. Such animals will not be affected directly by the nutritional, chemical, or morphological traits that determine the value of the plant as a food. This study reports on a filter-feeding amphipod, Ericthoniusbrasiliensis, that lives in domiciles it constructs by curling terminal segments of the green, calcified, and chemically defended seaweed Halimedatuna. We examined the temporal (1850s–1990s) and spatial (Caribbean, Mediterranean, and Pacific regions) scale of the association, the factors that may select for specialization on H. tuna, and the effect of the amphipod on growth of its host. Sampling along 125 km of coral reefs in the Florida Keys (USA) indicated that almost all populations of H. tuna had been colonized by this amphipod. Infested plants occurred on nine of ten reefs that supported H. tuna populations, with between 8 and 75% of the plants on those reefs colonized by the amphipod. For infested plants, 2–23% of all segments on each plant had been curled by the amphipod. Common co-occurring congeners of H. tuna (H. opuntia and H. goreaui) were never used for domicile construction. A survey of 1498 Halimeda specimens collected during the last 140 years and archived in the U.S. National Museum of Natural History (Smithsonian Institution, Washington, D.C.) indicated that the association has existed for >100 years and occurs throughout the Caribbean region, never in the Indo-Pacific or Mediterranean, and only on H. tuna. Predation by fishes could select for amphipod specialization on H. tuna. Laboratory experiments demonstrated that amphipods inhabiting curled segments of H. tuna were relatively immune from fish predation while those on the exterior surface of the plant or in open water were rapidly eaten. Segments of H. tuna are large enough to provide full protection from predators, while those of the co-occurring congeners H. goreaui and H. opuntia are of a size that may provide only partial protection. Experimental addition of E. brasiliensis to H. tuna plants in the field significantly decreased segment accumulation on infested relative to uninfested control plants. Whether this negative effect was a direct or indirect consequence of amphipod occupancy is unclear. Rolling plant portions into domiciles could directly decrease host growth by increasing shading and decreasing exposure of plant surface area to water column nutrient flux. Amphipod occupancy could indirectly slow net host growth if fishes selectively feed on plant sections occupied by amphipods. Underwater video showed that herbivorous fishes did not graze infested plants more than uninfested plants, but small predatory fishes did prefer feeding from infested plants. These non-herbivorous fishes may slow host growth by damaging the terminal meristematic tissues of plants during attacks on amphipods. This study demonstrates that habitat specialists can negatively impact hosts without consuming them and that specialization on a plant can occur due to its habitat value alone (as opposed to its value as a food). Received: 24 March 1998 / Accepted: 1 November 1998     

Marine yeasts as biocontrol agents and producers of bio-products

As some species of marine yeasts can colonize intestine of marine animals, they can be used as probiotics. It has been reported that β-glucans from marine yeast cells can be utilized as immuno-stimulants in marine animals. Some siderophores or killer toxins produced by marine yeasts have ability to inhibit growth of pathogenic bacteria or kill pathogenic yeasts in marine animals. The virulent factors from marine pathogens can be genetically displayed on marine yeast cells, and the yeast cells displaying the virulent factors can stimulate marine animals to produce specific antibody against the pathogens. Some marine yeast cells are rich in proteins and essential amino acids and can be used in nutrition for marine animals. The marine yeast cells rich in lipid can be used for biodiesel production. Recently, it has been reported that some strains of Yarrowia lipolytica isolated from marine environments can produce nanoparticles. Because many marine yeasts can remove organic pollutants and heavy metals, they can be applied to remediation of marine environments. It has been shown that the enzymes produced by some marine yeasts have many unique properties and many potential applications.     

Anolis lizards as biocontrol agents in mainland and island agroecosystems

Our knowledge of ecological interactions that bolster ecosystem function and productivity has broad applications to the management of agricultural systems. Studies suggest that the presence of generalist predators in agricultural landscapes leads to a decrease in the abundance of herbivorous pests, but our understanding of how these interactions vary across taxa and along gradients of management intensity and eco‐geographic space remains incomplete. In this study, we assessed the functional response and biocontrol potential of a highly ubiquitous insectivore (lizards in the genus Anolis) on the world's most important coffee pest, the coffee berry borer (Hypothalemus hampei). We conducted field surveys and laboratory experiments to examine the impact of land‐use intensification on species richness and abundance of anoles and the capacity of anoles to reduce berry borer infestations in mainland and island coffee systems. Our results show that anoles significantly reduce coffee infestation rates in laboratory settings (Mexico, p = .03, F = 5.13 df = 1, 35; Puerto Rico, p = .014, F = 8.82, df = 1, 10) and are capable of consuming coffee berry borers in high abundance. Additionally, diversified agroecosystems bolster anole abundance, while high‐intensity practices, including the reduction of vegetation complexity and the application of agrochemicals were associated with reduced anole abundance. The results of this study provide supporting evidence of the positive impact of generalist predators on the control of crop pests in agricultural landscapes, and the role of diversified agroecosystems in sustaining both functionally diverse communities and crop production in tropical agroecosystems.     

The effect of the presence of quiescent female nymphs, males and their spermatophores on spermatophore placement in two species of eriophyoid mites

Under sex dissociated sperm transfer, females seek spermatophores and pick up sperm without male assistance. In several species males adjust spermatophore deposition rate to the presence of conspecifics. It is not known, however, which factors could favor such elasticity in non-pairing males. In this paper, we compare male response towards conspecifics between the sex dissociated eriophyoid mites Aculus fockeui (Nalepa and Trouessart) and Aculops allotrichus (Nalepa). The species differ significantly in male reproductive strategies and, consequently, the intensity of male–male-competition. Aculus fockeui males deposit spematophores all over the leaves and occasionally leave single spermatophores beside quiescent female nymphs (QFNs). In contrast, A. allotrichus males guard QFNs and encircle them with spermatophores. In this study, males of both species deposited spermatophores close to and apart from the rival spermatophores. Aculops allotrichus males had similar spermatophore output whether they were kept alone or in a group of seven males. They did not change spermatophore output in the presence of five rival spermatophores, a QFN or a QFN and varying number of rivals, either. In contrast, A. fockeui males increased spermatophore output in the presence of rival spermatophores or when on the arena with a QFN the male number increased to eight males. They did not respond, however, to the presence of a QFN and one rival or a QFN alone. The possible effect of the species-specific intensity of male–male competition, population density, the availability of receptive females and the rate of spermatophore output on the flexibility of eriophyoid spermatophore deposition is discussed.     

Fungal pathogens of Euphorbia heterophylla and E. hirta in Brazil and their potential as weed biocontrol agents

A two-year survey of the fungi associated with two important congeneric pantropical weeds, Euphorbia heterophylla and E. hirta, was conducted in part of their native range in southern Brazil. Sampling was concentrated mainly in Rio de Janeiro State and ten species were identified as pathogens of these weeds. Two taxa, Botrytis ricini and Uromyces euphorbiae, were common to both weed hosts. Alternaria euphorbiicola, Bipolaris euphorbiae, Melampsora sp., Oidium sp. and Sphaceloma poinsettiae were recorded only from E. heterophylla, whereas Colletotrichum gloeosporioides, Sphaceloma sp. and Sphaerotheca fuliginea were restricted to E. hirta. Botrytis ricini and Colletotrichum gloeosporioides are new records for E. hirta, and Alternaria euphorbiicola and Sphaerotheca fuliginea are new host records for Brazil. Bipolaris euphorbiae, previously identified as Helminthosporium sp., is considered to be the correct name for the causal agent of a major disease of E. heterophyllum in Brazil. The potential of these pathogens as biocontrol agents is discussed and the mycobiota associated with both these weeds worldwide is reviewed.This revised version was published online in October 2005 with corrections to the Cover Date.     

Intracellular antibodies and challenges facing their use as therapeutic agents

A key feature of antibodies is their ability to bind antigens with high specificity and affinity. This has led to the concept of intracellular antibodies (intrabodies), designed to mimic antibody-antigen binding, but inside cells. Antibody fragments comprising the antigen-binding variable domains are convenient formats for intrabodies, potentially allowing for intracellular functionality. Intrabodies are promising tools, capable of interfering with a wide range of molecular targets in various intracellular compartments. However, many significant challenges remain to be overcome before intrabodies can be useful therapeutic agents. Although major progress has been made in the design and selection of intrabodies, new developments and advances are needed to allow their efficient delivery and expression for treatment of human diseases.     

Unsuccessful introduced biocontrol agents can act as pollinators of invasive weeds: Bitou Bush (Chrysanthemoides monilifera ssp. rotundata) as an example

The extent of self‐compatibility and reliance on pollinators for seed set are critical determinants of reproductive success in invasive plant species. Seed herbivores are commonly used as biocontrol agents but may also act as flower visitors, potentially resulting in pollination. However, such contrasting or potentially counterproductive interaction effects are rarely considered or evaluated for biological control programs. We investigated the breeding system and pollinators of Bitou Bush (Chrysanthemoides monilifera ssp. rotundata), an invasive species in Australia that has been the subject of biocontrol programs since 1987. We found the species to be obligate outcrossing in all six populations tested. From 150 video hours, we found 21 species of potential pollinators, including Mesoclanis polana, the Bitou Seedfly, native to South Africa and released in Australia as a biocontrol agent in 1996. Mesoclanis polana transferred pollen to stigmas and was the most common pollinator (52% of pollinator visits), followed by the syrphid fly Simosyrphus grandicornis (9%) and introduced honeybee, Apis mellifera (6.5%). Fruit‐to‐flower ratios ranged from 0.12 to 0.45 and were highest in the population with the greatest proportion of Mesoclanis polana visits. In an experimental trial, outside the naturalized range, the native bee Homalictus sphecodoides and the native syrphid Melangyna viridiceps were the primary pollinators, and fruit‐to‐flower ratios were 0.35, indicating that Bitou Bush would have ready pollinators if its range expanded inland. Synthesis. Invasive Bitou Bush requires pollinators, and this is effected by a range of generalist pollinators in eastern Australia including the Bitou Seedfly, introduced as a biocontrol agent, and the major pollinator detected in this study. Fruit‐to‐flower ratios were highest when the Bitou Seedfly was in high abundance. This study underscores the importance of evaluating the pollination biology of invasive species in their native ranges and prior to the introduction of biocontrol agents.     

生防真菌耐旱特性的生理生化基础及其利用

丝孢类生防真菌常需满足高湿度条件才能萌发和侵染害虫,已成为广泛应用真菌杀虫剂控制害虫的重要限制因素,适当的剂型化技术在一定程度上能够降低菌剂对环境湿度的依赖性,但生防真菌侵染体本身的耐旱性对菌剂的环境适应性起决定性作用,文中回顾和评述了近20多年来国际上生防真菌耐旱性研究与利用的主要进展,分析和总结了生防真菌耐旱性的生理生化基础及其水活度调控原理,讨论了提高低分子多元醇及海藻糖等生物学相容溶质在侵染体内积聚而增强菌剂耐旱性的可能途径．认为认识决定耐旱性的胞内相容溶质积累的分子生物学基础及其调控机理,探索建立从生理生化水平上最大限度地增强生防菌剂耐旱性的新工艺,是今后生防真菌基础与应用研究的重要方向。