Release Of Natural Enemies Research Articles

IMPACT AND MANAGEMENT OF THE HORSE CHESTNUT LEAF-MINER (CAMERARIA OHRIDELLA)

Summary The horse chestnut leaf-miner (Cameraria ohridella Deschka & Dimić) is a new pest of horse chestnut that established in the UK in 2002. Experience from Europe indicates that where the moth has become established, it will cause severe damage to the foliage of horse chestnut on an annual basis, and defoliation before normal leaf-fall in the autumn. However, it appears that most damage caused by C. ohridella occurs too late in the season to have a major impact on the vitality of horse chestnut. There is no evidence from Europe that trees have died, or shown a progressive decline in health, as a direct consequence of C. ohridella attack. Nevertheless, there are advantages in implementing controls to reducc infestation. Any reduction in damage, especially in built-up areas, will help to maintain tree health and ensure survival, and this could be more important in the UK, because of differences in climate and interactions with other insect pests and diseases. C. ohridella can be controlled with chemical insecticides, but these are difficult to apply safely and efficiently to large trees, are expensive, and pose environmental hazards. A much safer and more practical means of control is to remove fallen leaves during the autumn and winter. These can then be either composted thoroughly or burnt, to destroy the over-wintering pupae, or, where collected into smaller heaps, as in gardens, covered with a layer of soil or other plant material to prevent adult emergence. In the long-term, it is expected that permanent and sustainable control of C. ohridella will be achieved through the introduction and release of natural enemies from the moth's area of origin.

Consumer preferences and willingness to pay for biological control in the urban landscape

Urban and suburban residents have more contact with the landscape environment than with any other exterior environment. They place high value on the aesthetic quality of the urban landscape and express significant concerns about managing insect herbivores that damage trees and shrubs. A comprehensive survey was initiated to assess the preference of urban residents for three pest management approaches (chemical pesticide, biorational insecticide, or introduction of a specific natural enemy) to control an introduced urban forest pest. Potential survey participants were initially contacted by telephone. Those agreeing to be interviewed were provided with written background information on the pest, the control options, and given one of 48 different cost and program attribute scenarios for implementation of the three approaches. They were contacted a second time by telephone for a final survey that asked them whether they were willing to pay the annual cost for the program attributes stated in their survey. Release of natural enemies was the overwhelming first choice among control options and application of chemical insecticides was least favored. When the price of all options was low, the respondents preferred the biological control option. As prices for all options rose, the chemical and bacterial options increased in preference, but when prices became high, preferences shifted again to the natural enemy option. The social characteristics of respondents favoring the different options were also examined in a contingent valuation analysis. From the survey, it was possible to calculate a respondent’s annual willingness to pay $485 for the natural enemy option, $131 for the bacterial spray option, and $23 for the chemical pesticide option. The results suggest that it may be possible to generate social and financial support from urban residents for introduction/classical biological control programs for landscape insect pests.

A simple criterion for successful biological control on annual crops

AbstractPopulation dynamics of pest insect‐natural enemy systems on annual crops is quite different from those seen in classic biological control programes. On an annual crop, for example, the persistence of populations of pest insects is forced to terminate when crops are harvested. Pest control on annual crops aims to suppress the maximum density of the pest below a certain level, and a low level equilibrium is not always the aim. It is important to determine the initial impact just after release of a natural enemy in order to determine the success of a biological control program. Therefore, effectiveness of natural enemies should be evaluated by prediction of such short‐term population dynamics. This paper presents a new and simple analytical model for successful biological control on annual crops. A criterion of successful biological control is given as the ratio of the pest and natural enemy populations just when the pest begins to decrease. This ratio is derived from the intrinsic rates of natural increase of both populations and the daily total predation by natural enemies. Using this model, criteria on appropriate number and time of release of natural enemies are obtained. The practical applications of this model are discussed with respect to evaluating the success or failure of natural enemy releases in future biological control programs.

Invasiveness of Some Biological Control Insects and Adequacy of Their Ecological Risk Assessment and Regulation

Abstract: The problem of invasive species has reignited interest in biological control as a management tool. Classical biological control involves deliberate release of exotic natural enemies into new environments in an attempt to limit the density of an invasive species. Persistent, sustained limitation of invasive species by coevolved natural enemies is a seductive concept. Evidence now suggests, however, that biological control through the release of natural enemies can carry unanticipated ecological risks. There have been ecological side effects of distributing a deliberately introduced weevil ( Rhinocyllus conicus ) and an adventitious weevil ( Larinus planus ) for the biological control of exotic thistles. Both weevils have had major direct effects on key population‐growth parameters of native thistles, and R. conicus has had an indirect effect on the interaction between a thistle and a native insect. These findings led us to review how ecological risk is evaluated, and to ask whether pre‐release tests can predict the types of ecological effects documented. We conclude that, when done thoroughly, the tests used can determine host specificity by identifying physiological host range, but the usual tests cannot be relied upon to predict the ecological host range or impact on populations of less‐preferred but accepted native species. Our data provide support for suggestions that the behavioral and developmental data now taken need to be supplemented with additional data on population parameters to better predict field‐host use, population growth, interaction strengths, and ecological outcomes for native species that are potential hosts.

Environmental risk assessment of exotic natural enemies used in inundative biological control

In the past 100 years many exotic naturalenemies have been imported, mass reared andreleased as biological control agents. Negativeenvironmental effects of these releases haverarely been reported. The current popularity ofinundative biological control may, however,result in problems, as an increasing number ofactivities will be executed by persons nottrained in identification, evaluation andrelease of biological control agents.Therefore, a methodology for risk assessmenthas been developed within the EU-financedproject `Evaluating Environmental Risks ofBiological Control Introductions into Europe[ERBIC]' as a basis for regulation of importand release of exotic natural enemies used ininundative forms of biological control (i.e.not in `classical biological control' thoughsome of the same principles and approachesapply). This paper proposes a general frameworkof a risk assessment methodology for biologicalcontrol agents, integrating information on thepotential of an agent to establish, itsabilities to disperse, its host range, and itsdirect and indirect effects on non-targets. Ofthese parameters, estimating indirect effectson non-targets will be most difficult, asmyriads of indirect effects may occur whengeneralist natural enemies are introduced. Theparameter `host range' forms a central elementin the whole risk evaluation process, becauselack of host specificity might lead tounacceptable risk if the agent establishes anddisperses widely, whereas, in contrast, amonophagous biological control agent is notexpected to create serious risk even when itestablishes and disperses well. Drawing onpublished information and expert opinion, theproposed risk assessment methodology is appliedto a number of biological control agentscurrently in use. These illustrative casehistories indicate that the risk assessmentmethodology can discriminate between agents,with some species attaining low `risk indices'and others scoring moderate or high. Riskindices should, however, not be seen asabsolute values, but as indicators to which ajudgement can be connected by biologicalcontrol experts for granting permission torelease or not.

Habitat Associations of Euphorbia and Aphthona Species from Europe: Development of Predictive Models for Natural Enemy Release with Ordination Analysis

Abstract Biotic and abiotic factors can have a profound influence on the occurrence, species composition, structure, distribution, relative abundance, and dynamics of plant species and their associated natural enemies. Elucidation of some of the more relevant habitat characteristics for a pestiferous plant or phytophage species in its place of origin may enable better prediction of its rates of colonization and spread should it accidentally be introduced into new areas. A similar analysis of the habitat requisites for the associated natural enemies of the plant/phytophage should enable the development of predictive models that identify habitat factors conducive to the establishment and impact on the particular plant or phytophage species. In this study, habitat associations were characterized for four different Euphorbia species and their associated flea beetle species in the Aphthona complex from 17 field sites in Europe, representing xeric, mesic, and hydric habitats. Micro- and macronutrient analyses were conducted on soil and spurge foliage and roots; physical properties of the soil were analyzed; plant cover of grasses, forbs (a broad-leaved herbaceous plant), and Euphorbia species (and total plant productivity) were estimated at each of the sites, and relative abundance counts were made for each of the flea beetle species at each of the 17 sites during spring, early summer, and mid-summer 1991. Spurge species included Euphorbia cyparissias, E. lucida, E. seguieriana, and E. virgata. Flea beetles species included Aphthona cyparissiae, A. czwalinae, A. lacertosa, A. nigriscutis, A. pygmaea, A. venustula, and A. violacea. Ordination models generated for the spurge species suggested that E. virgata and E. lucida were associated with higher levels of soil matric potential, clay, organic matter, Ca, Fe, K, Mg, N, P, Zn (soil layer B ), and plant productivity. In contrast, E. cyparissias and E. seguieriana were associated with relatively lower levels of plant productivity and higher levels of sand, CaCO 3 , and Zn (soil layer A ). Ordination models developed for the Aphthona species suggested that A. czwalinae and A. lacertosa were associated with sites containing higher levels of clay and plant productivity and higher levels of Mn in the Euphorbia roots; A. violacea was associated with sites with intermediate levels of sand, clay, and plant productivity, in addition to spurge roots with higher levels of Cu, Fe, K, N, P, and Zn. A. nigriscutis was associated with sandier soils with lower levels of plant productivity and higher levels of Ca, K, and N in the Euphorbia roots. A. cyparissiae, A. pygmaea, and A.venustula were associated with moderately sandy soils with relatively lower levels of plant productivity and Euphorbia species with higher levels of Ca and N in the roots. The ordination models generated from this study provide the diagnostic framework for the identification of appropriate habitats and key site requisites that might be conducive to the establishment and impact of the Aphthona species on leafy spurge in North America.

Host Range Testing of Insects for Biological Weed Control: How Can It Be Better Interpreted?

I nonindigenous species cause major environmental damage in many different ecosystems worldwide. In a recent assessment, the costs to the US economy inflicted by invasive species were estimated at $137 billion annually (Pimentel et al. 2000). The US government therefore has expanded its efforts to combat exotic pests, as well as to accelerate research on habitat restoration and biologically based, integrated pest management tactics. Classical biological control (that is, the deliberate release of natural enemies to control exotic pests) is an important tool in integrated pest management, and it is usually considered to be economically sound and environmentally safe. However, safety of classical biological control has recently become a matter of debate concerning the risks posed by the introduced enemies to nontarget organisms and to biodiversity in general. This shift in the assessment of biological control arose mainly from recent findings of nontarget effects caused by biocontrol agents introduced through classical biological control programs (Simberloff and Stiling 1996, Louda et al. 1997, Strong 1997). The importance of the topic emerged in subsequent publications discussing such topics as benefits of biological control (Gurr and Wratten 2000), ecological relevance of nontarget attack (Follet and Duan 2000, Wajnberg et al. 2001), evolutionary stability (Jervis 1997), and the use of modeling in biological control (Thomas and Willis 1998). One of the most critical points of contention is whether and to what extent host-specificity tests of potential biocontrol agents are useful in assessing potential risks toward nontarget organisms (McEvoy 1996). Although prerelease studies in general, and host range testing in particular, only recently have begun to be part of biological control programs against insect pests, they have a long-standing tradition in the classical biological control of weeds. The report of host range expansion of the weevil Rhinocyllus conicus Froel. (Figure 1; Louda et al. 1997), introduced in North America to control exotic thistles, has therefore puzzled many environmentalists and theoretical ecologists and has contributed to a general discomfort about the effectiveness of prerelease studies. In this paper, I discuss the potential and limits of host range testing in predicting ecological and evolutionary changes in the host range of biocontrol agents after their release in a target area. Particular emphasis is placed on the usefulness of detailed behavioral and genetic studies in improving the interpretation of standard host range tests.

Invasion thresholds for fungicide resistance: deterministic and stochastic analyses

Fungicide resistance is an important practical problem, but one that is poorly understood at the population level. Here we introduce a simple nonlinear model for fungicide resistance in botanical epidemics which includes the dynamics of the chemical control agent and the host population, while also allowing for demographic stochasticity in the host-parasite dynamics. This provides a mathematical framework for analysing the risk of fungicide resistance developing by including the parameters for the amount applied, longevity and application frequency of the fungicide. The model demonstrates the existence of thresholds for the invasion of the resistant strain in the parasite population which depend on two quantities: the relative fitness of the resistant strain and the effectiveness of control. This threshold marks a change from definite elimination of the resistant strain below the threshold to a finite probability of invasion which increases above the threshold. The fungicide decay rate, the amount of fungicide applied and the period between applications affect the effectiveness of control and, consequently, they influence whether or not resistance develops and the time taken to achieve a critical frequency of resistance. All three parameters are amenable to control by the grower or by coordinating the activity of a population of growers. Providing crude estimates of the effectiveness of control and relative fitness are available, the results can be used to predict the consequences of changing these parameters for the risk of invasion and the proportion of sites at which this might be expected to occur. Although motivated for fungicide resistance, the model has broader application to herbicide, antibiotic and antiviral resistance. The modelling approach and results are discussed in the context of resistance to chemical control in general.

Release, Establishment and Spread of Asian Natural Enemies of Euonymus Scale (Homoptera: Diaspididae) in New England

Release, Establishment and Spread of Asian Natural Enemies of Euonymus Scale (Homoptera: Diaspididae) in New England

PAIRWISE ASSOCIATION AS A CRITERION FOR THE SELECTION OF COLLECTION SITES OF NATURAL ENEMIES OF THE CASSAVA GREEN MITE, Mononychellus tanajoa (BONDAR)

Climatic similarity has been the primary parameter considered in the selection of sites for the collection and release of natural enemies in classical biological control programs. However, acknowledging the relevance of the composition of biological communities can be essential for improving the record of successful biocontrol projects, in relation to the proper selection of collection sites. We present in this paper an analysis of the plant and mite assemblages in cassava fields of northeastern Brazil. Such analysis is suggested as an additional criterion for the selection of collection sites of mite predators of the cassava green mite, Mononychellus tanajoa (Bondar), in an international biological control program. Contingency TABLES were built using Dice's index as an indicator of significant associations between pairs of species. This analysis enabled the identification of plant and mite species typically found together, indicating interspecific interactions or similar ecological requirements. Finally, a cluster analysis was used to group sites containing similar assemblages. These sites exhibit comparable chances of harboring a given species. Applied at the species-group level, the analysis may assist in better defining sites for the collection of natural enemies to be released in a given region, improving the chances of establishment.

Introduction, release and recovery of several exotic natural enemies for biological control of the citrus leaf miner,Phyllocnistis citrella, in Israel

The citrus leafminer,Phyllocnistis citrella Stainton, was first discovered in citrus groves in Israel in 1994. A biological control project was launched immediately and six species of natural enemies of the pest were introduced from Thailand, China, Australia and Florida. These were reared and released in citrus groves. At present, most have been recovered from the release sites and some seem to have become established, with relatively high rates of parasitization. The current status of the pest and of its indigenous and introduced natural enemies is briefly discussed.

Biological Control of Bemisia argentifolii (Homoptera: Aleyrodidae) Infesting Euphorbia pulcherrima : Evaluations of Releases of Encarsia luteola (Hympenoptera: Aphelinidae) and Delphastus pusillus (Coleoptera: Coccinellidae)

Releases of Encarsia luteola Howard and Delphastus pusillus LeConte were evaluated for their ability to control Bemisia argentifolii Bellows & Perring, n. sp. greenhouse-grown poinsettias. Three treatments, each replicated three times, were used to assess the impact of natural enemy releases on B. argentifolii populations: (1) a complete exclusion of natural enemies cage, (2) an identical exclusion cage receiving natural enemy releases as a control for cage effects, and (3) releases of natural enemies onto plants within the greenhouse but outside of either cage. Weekly releases of the parasitoid E. luteola were initiated the week the plants entered the greenhouse and three releases of D. pusillus , 1 wk apart, were made when B. argentifolii populations rose dramatically 9 wk into the trial. Release rates for both natural enemies were one insect per plant per week. Weekly collected leaf samples were examined with the aid of a dissecting microscope. The numbers of live whiteflies were recorded by developmental stage as were the numbers of dead (resulting from natural causes, D. pusillus predation, or E. luteola host-feeding) and parasitized whitefly nymphs. The lack of a significant difference in whitefly densities between the two natural enemy release treatments suggested the absence of a cage effect on whitefly populations. Whitefly densities within the complete exclosure cages were significantly greater than the whitefly densities in either of the two natural enemy release treatments, indicating a significant impact of natural enemy releases on B. argentifolii infestations. Whitefly damage to harvested plants within the natural enemy release areas was not significantly different from the damage level observed in the grower-treated area. The direct cost associated with B. argentifolii biological control (166.32 per greenhouse section) was ≍5 times greater than the insecticide-based B. argentifolii management program currently used by poinsettia growers. This cost differential can be reduced if the indirect environmental and worker-safety costs associated with insecticide use are included, and further reductions should accompany increased commercial availability of D. pusillus.

Hemipterous predators of eucalypt defoliator caterpillars

In Brazil, plantations of Eucalyptus have increased significantly, mainly as monocultures. As a result of the large planting programmes, damage due to insect attacks and diseases has been registered. Several methods of control have been used, but biological control, by rearing and release of natural enemies, seems to be an efficient method with low cost, and less social and ecological problems than chemical methods. The Forest Entomology Laboratory at the Federal University of Viçosa, in Brazil, has successfully identified the major predators of eucalypt defoliator caterpillars. Studies were concentrated on the description of these insects, their diets, prey, habitat, and also, methods of capture and reproduction in laboratory conditions.

Toward Predictable Biological Control of Liriomyza trifolii (Diptera: Agromyzidae) Infesting Greenhouse Cut Chrysanthemums

Implementation of augmentative biological control is often hindered by the inability to obtain accurate information on natural enemy release rates that will ultimately yield a salable crop within economic constraints. The purpose of this study was to develop and evaluate a computer model that attempts to predict augmentative releases of the parasitoid Diglyphus begini (Ashmead) (Hymenoptera: Eulophidae) to use for biological control against the serpentine leafminer Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) infesting greenhouse-grown cut chrysanthemums. The model attempts to determine the appropriate release rate necessary to reduce leafminer densities below 1 larvae per 1,000 chrysanthemum leaves within 40 d after planting, after which time aesthetically important foliage forms on chrysanthemums. In the construction of this deterministic model, three simplifying assumptions have been made: (1) there is no insect movement between the greenhouse and outside, (2) greenhouse temperatures are a constant 27°C, and (3) the greenhouse represents a homogeneous environment. Model simulations indicated that successful biological control was unlikely when parasitoid releases are initiated later than 14 d after planting regardless of the release rate. The simulations also demonstrated that D. begini release rates are not linearly related to L. trifolii densities, and that a parasitoid release strategy is not simply the determination of a proper wasp/leafminer ratio. Validation studies of the model's predictions provided mixed results. Following the release rates generated by the model, L. trifolii larval densities were not significantly greater than I per 1,000 leaves 40 d after planting. However, the model did not always track the succession and magnitude of leafminer population fluctuations with statistical accuracy. Two factors probably contributed to these errors in prediction: (1) the assumptions inherent to the model were not met during the validation trials, and (2) the leafminer subroutine of the model could not accurately predict L. trifolii densities in the absence of D. begini . In spite of these errors, leafminer damage to the harvested foliage was significantly lower in the treatments receiving D. begini releases than in the control treatments. In addition, when the model was tested in a commercial cut chrysanthemum greenhouse, L. trifolii was successfully controlled by releases of D. begini , resulting in the production and harvest of a salable cut chrysanthemum crop without the use of any pesticides. Finally, postvalidation reconstruction of the model, to include temperature-dependent variation in life history parameters, increased the predictive power of the model.

Natural enemies and forest pest management

Forest insect pest management differs from pest management in other renewable-resource industries because of the relative complexity and stability of the forest environment. An important component of this complexity is the rich fauna of natural enemies attacking most forest insect pests. Understanding the relationship between forest insect pests and their natural enemies would permit better insight into the dynamics of pest populations.The active release of natural enemies in inoculative or inundative release strategies is a direct application of biological control to pest management. The conservation of resident natural enemies is an indirect biological control method with great potential. Knowledge of the ecology of natural enemies can be used to modify other forest practices such as reforestation and insecticide use to conserve or enhance the action of natural enemies.

Low‐Input/Sustainable Agricultural Research and Education—Challenges to the Agricultural Economics Profession

Over the past decade, a number of different terms have been used to describe agricultural technologies that seek to substitute management and scientific knowledge for synthetic chemical pesticides and fertilizers-terms such as organic, regenerative, alternative, sustainable, and reduced-input have become widely used in various contexts (Wagstaff; Lowrance, Hendrix, and Odum). The term is used in California and other states to describe their new research and education programs. The term low-input has become the latest entry in the vocabulary of agricultural technology because this term is used in the FY 1988 federal appropriations legislation. Low-input/sustainable agriculture encompasses a wide array of approaches to farming that reduce the farmer's dependence on certain kinds of purchased inputs in ways that increase profits, reduce environmental hazards, and ensure a more sustainable agriculture for generations to come. Low-input farming methods range from release of exotic natural enemies to rather commonplace methods such as controlling weeds by mechanical cultivation and crop rotations. Also included in this category are various integrated pest management strategies such as biological control of pests through enhancement of natural enemies, use of legume crops in place of some purchased fertilizers, and application of livestock manures and compost. A low-input/sustainable farming system is a combination and sequence of low-input farming methods or technologies integrated into a whole-farm managerial plan. While many of the concepts underlying low-input farming methods have been known for decades or even centuries, the essence of this approach is not a reversion to the technologies of previous decades or centuries but a combination of the best of modern agricultural science and technology with the practical experience of farmers who are profitably substituting management for most or all of their purchased inputs of synthetic chemical pesticides and fertiliz-

Economics of the cassava mealybug [Phaenacoccus Manihoti; Hom.: Pseudococcidae] biological control program in Africa

Critical analyses of current pest control practices and the role of classical biological control are needed. The costs and benefits of the introduction and release of natural enemies of the cassava mealybug are assessed. A conservative estimate shows that the benefit to cost ratio of this project is extremely high (149∶1).

Technology for automated aerial release of natural enemies of the cassava mealybug and cassava green mite

An automatic insect release system (AIRS) has been developed by the International Institute of Tropical Agriculture in collaboration with Firma Dieringer of Austria and Ciba-Pilatus (now Zimex Aviation) of Switzerland for the aerial distribution of natural enemies of two cassava pests—cassava mealybug (Phenacoccus manihoti) and cassava green mite (Mononychellus tanajoa). The AIRS, installed in a twin turbo-prop aircraft, has undergone a series of tests to evaluate suitable packaging substrates, pre- and post-release mortality, biological performance and ground distribution of natural enemies.Preliminary results show 25% of the mealybug parasitoid, Epidinocarsis lopezi died from packaging to release, maximum 25% died during the release and minimum 50% survived. The mortality of predatory mites released in small packages was negligible. Further work on post-release survival and dispersal is needed.

Development of Integrated Pest Management Strategies in Floricultural Crops

Development of integrated pest management strategies in floriculture has lagged far behind the development of strategies in other agricultural crops. Shorrterm solutions to immediate arthropod pest problems through application of the appropriate pesticides has been, and continues to be, a major focus of research programs in floricultural entomology. Few studies have been completed on development of statistically valid sampling plans, management of insecticide resistance, phenological monitoring of arthropod pests, evaluation and release of natural enemies, and other strategies designed to increase efficiency of chemicals if they are needed. We discuss possible reasons for the lack of research in these areas and outline the development of pest management strategies for chrysanthemums to demonstrate the feasibility of this approach in floriculture.

導入天敵によるヤノネカイガラムシの生物的防除 Ｉ あま美大島における放飼効果

導入天敵によるヤノネカイガラムシの生物的防除 Ｉ あま美大島における放飼効果