Enemies For Biological Control Research Articles

Beauveria Bassiana; Insect Pathogen And Biopesticide Producer As An Effective And Environmentally Friendly Alternative For Biological Control

Beauveria bassiana is one of the insect pathogens that can be used as a biological control agent. The interaction between Beauveria bassiana and other natural enemies in biological control can affect the effectiveness of pest control as a biopesticide. The efficacy of these fungi was also influenced by the toxin produced (beauvericin, bassianin, bassiacridin, beauvericin, bassianolide, cyclosporine, oosporein, and tenellin) which may interfere the nervous system and kill the target insects. The use of chemical pesticides, which has been one of the farmers’ choices in pest control, has negative impacts on the environment, human health, and pest resistance therefore, B. bassiana as an alternative, biological pest control and biological control are increasingly considered as environmentally friendly and sustainable control methods, so that biological control can become an important alternative to reduce the use of chemical pesticides. Facing this problem, alternative methods including the use of entomopathogenic fungi as biopesticide could be a sound measure to preserve the environment, biodiversity and ensure good quality of crops.

A parasitoid's dilemma between food and host resources: the role of volatiles from nectar-providing marigolds and host-infested plants attracting Aphidius platensis.

The use of nectar-producing companion plants in crops is a well-known strategy of conserving natural enemies in biological control. However, the role of floral volatiles in attracting parasitoids and effects on host location via herbivore-induced plant volatiles is poorly known. Here, we examined the role of floral volatiles from marigold (Tagetes erecta), alone or in combination with volatiles from sweet pepper plant (Capsicum annuum), in recruiting Aphidius platensis, an important parasitoid of the green peach aphid Myzus persicae. We also investigated whether marigold floral volatiles are more attractive to the parasitoid than those emitted by sweet pepper plants infested by M. persicae. Olfactometry assays indicated that floral volatiles attracted A. platensis to the marigold plant and are more attractive than sweet pepper plant volatiles. However, volatiles emitted by aphid-infested sweet pepper were as attractive to the parasitoid as those of uninfested or aphid-infested blooming marigold. The composition of volatile blends released by uninfested and aphid-infested plants differed between both blooming marigold and sweet pepper, but the parasitoid did not discriminate aphid-infested from uninfested blooming marigold. Volatile released from blooming marigold and sweet pepper shared several compounds, but that of blooming marigold contained larger amounts of fatty-acid derivatives and a different composition of terpenes. We discuss the potential implications of the aphid parasitoid attraction in a diversified crop management strategy.

Efficiency of Three Egg Parasitoid Species on Fall Armyworm (Lepidoptera: Noctuidae) in Laboratory and Field Cages

Abstract Egg parasitoids are the most used natural enemies in biological control of Spodoptera frugiperda (J.E. Smith), a pest of gramineous plants native to the Americas that recently invaded Africa and some countries of Asia. Although Trichogramma pretiosum (Riley) is one of the main species used against this pest, there are other species with equal or greater parasitism potential. The objective of this work was to compare, in laboratory and in field cages, the parasitism of Telenomus remus Nixon, Trichogramma atopovirilia (Oatman and Platner), and T. pretiosum on S. frugiperda eggs. Telenomus remus and T. atopovirilia reached the highest percentages of parasitism in laboratory (>70%) which did not differ statistically from each other. Trichogramma pretiosum had the lowest percentage of parasitism (29%) of the three. In the field cage assays, Te. remus parasitized 30% of the S. frugiperda egg masses, and T. pretiosum parasitized about 7.5% of the egg masses. These results underscore the importance of adequate selection of egg parasitoids for their use in biological control programs by augmentation against S. frugiperda.

The Pupal Pigmentation Pattern and Pupal Development in the Species of Aphytis Howard (Hymenoptera: Aphelinidae).

Simple SummaryAphytis species (Hymenoptera: Aphelinidae) have been considered as the most important natural enemies in biological control of armoured scale insects (Hemiptera: Diaspididae). However, it is difficult to identify the species of the genus, particularly that of the A. lingnanensis group, based on adult morphological characters. Although the differences in pupal pigmentation of Aphytis species have been documented previously, they have not been much used as taxonomic characters for Aphytis species identification. In this study, we present four characteristic pigmentation patterns of Aphytis pupae, together with photographs, including the categories of: entirely yellow, partly dark brown, entirely or predominantly black, and partly black pupae. No significant intra-specific variation in pupal colour pattern was detected despite relatively high numbers of specimens examined, many from multiple, and different, origins. We summarize the present status of pupal pigmentation in the described species of Aphytis, according to the species groups, which could be used as an important supplementary diagnostic character for distinguishing species of Aphytis, especially closely-related species.Species identification of Aphytis on the basis of adult morphology is extremely difficult, especially in the A. lingnanensis group, with several cryptic species. Pupal pigmentation could be used as one of the taxonomic characters for Aphytis species, and in some instances, pupal pigmentation actually provided the first clue to the distinctness of cryptic Aphytis species. The present study investigated the full-grown larvae or younger pupae of Aphytis species, and pupal pigmentation and pupal development were observed and photographed. Four characteristic pigmentation patterns of Aphytis pupae were summarized including: entirely yellow, partly dark brown, entirely or predominantly black, and partly black. The species in the chilensis and mytilaspidis groups, and some unassigned species, generally have entirely, or predominantly and or partly black pupae. The species in the chrysomphali, funicularis, and proclia groups generally have the pupae entirely yellow. The species of the lingnanensis group have the pupae both entirely yellow, e.g., A. fisheri, and partly dark brown pupae, e.g., A. lingnanensis, A. holoxanthus and A. melinus. The pupae of Aphytis species in this study had a developmental duration of about 5–8 days at 27 ± 1 °C, 70 ± 5% RH and a photoperiod of 10L: 14D. It was found that the pupal skin was always melanized at the beginning stage, generally in the first day, among the pigmented pupae of Aphytis species. As development continued, the pigmentation became darker and the eye colour changed from pale red/brown to green. No significant intra-specific variation in pupal colour pattern was detected despite relatively high numbers of specimens examined, many from multiple, and different, origins. Overall, our study indicates that pupal pigmentation could be more helpful in species identification of Aphytis.

A DNA barcode reference library of Neuroptera (Insecta, Neuropterida) from Beijing.

Neuroptera (lacewings) is one of the ancient holometabolous insect groups, but some extant species stand as important natural enemies for biological control. As the capital city of China, Beijing has a rich fauna of Neuroptera, previously with 47 species recorded and sorted in 32 genera of seven families. In this study, DNA barcoding based on sequences of COI gene fragments is used to discriminate lacewing species from Beijing. 217 DNA barcode sequences belonging to 49 species were successfully obtained. The COI barcode data worked well for identification of almost all lacewing species herein examined except Pseudomalladaprasinus (Burmeister), in which cryptic species may exist. Twenty species of Neuroptera are newly recorded from Beijing. Besides, Nothochrysinae is first recorded from Beijing. Chrysopidiaciliata (Wesmael) and Drepanepteryxalgida (Erichson) are first recorded from China.

Assessing the augmentation of Amblydromalus limonicus with the supplementation of pollen, thread, and substrates to combat greenhouse whitefly populations

Due to issues with establishment and persistence of natural enemies in biological control, the provision of alternative food sources and oviposition sites are important factors to enhance pest control. In this study, three different supplementation treatments were examined for their ability to increase the populations of the predatory mite Amblydromalus limonicus, and its implications for greenhouse whitefly control on peppers and eggplants. These were: (1) pollen (Typha orientalis), (2) pollen and thread, (3) pollen, thread, and a substrate mixture of buckwheat, gorse, and rice husks, which were compared to a control treatment that had no supplementation. Significant treatment effects were found on pepper for A. limonicus (mite eggs p = 0.008, mobile mites p = <0.0001). The predatory mite successfully established and persisted at high population levels in the pollen-thread, and pollen-thread-substrate treatments. All supplementation treatments were able to control whitefly populations on peppers, while the control treatment failed to. The results obtained were formulated into possible application techniques for greenhouse growers to utilise.

English

English

Exotic biological control agents: A solution or contribution to arthropod invasions?

Biological control is a valuable and effective strategy for controlling arthropod pests and has been used extensively against invasive arthropods. As one approach for control of invasives, exotic natural enemies from the native range of a pest are introduced to areas where control is needed. Classical biological control began to be used in the late 1800s and its use increased until, beginning in 1983, scientists began raising significant concerns and questions about nontarget and indirect effects that can be caused by these introductions. In recent years, similar issues have been raised about augmentative use of exotic natural enemies. Subsequently, international guidelines, national regulations and scientific methods being used for exotic natural enemies in biological control have changed to require appropriate specificity testing, risk assessment and regulatory oversight before exotic natural enemies can be released. National and international standards aimed at minimizing risk have increased awareness and promoted more careful consideration of the costs and benefits associated with biological control. The barriers to the implementation of classical and augmentative biological control with exotic natural enemies now are sometimes difficult and, as a consequence, the numbers of classical biological control programs and releases have decreased significantly. Based in part on this new, more careful approach, classical biological control programs more recently undertaken are increasingly aimed at controlling especially damaging invasive arthropod pests that otherwise cannot be controlled. We examine evidence for these revised procedures and regulations aimed at increasing success and minimizing risk. We also discuss limitations linked to the apparent paucity of post-introduction monitoring and inherent unpredictability of indirect effects.

Encounters with aphid predators or their residues impede searching and oviposition by the aphid parasitoid Aphidius ervi (Hymenoptera: Aphidiinae)

Intraguild predation (IGP) can be an important factor influencing the effectiveness of aphid natural enemies in biological control. In particular, aphid parasitoid foraging could be influenced by the presence of predators. This study investigated the effect of larvae of the predatory hoverfly Episyrphus balteatus DeGeer (Diptera: Syrphidae) and the multicolored Asian ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae) on the foraging behavior of the aphid parasitoid, Aphidius ervi Haliday (Hymenoptera: Aphidiidae) in choice experiments using a leaf disc bioassay. Wasp response to chemical tracks left by those predator larvae was also tested. Parasitoid behavior was recorded using the Observer (Noldus Information Technology, version 5.0, Wageningen, the Netherlands). The experiments were conducted under controlled environmental conditions using leaves of the broad bean plant, Vicia faba L. (Fabaceae) with Myzus persicae Sulzer (Homoptera: Aphididae) as the host complex. A. ervi females avoided aphid patches when larvae of either predator were present. A similar avoidance response was shown by A. ervi to aphid patches with E. balteatus larval tracks, whereas no significant response was observed to tracks left by H. axyridis larvae. It was concluded that IG predator avoidance shown by the aphid parasitoid A. ervi may be a factor affecting their distribution among host patches.

Utilization of prey-rich patches leads to reproductive advantages for clustered individuals of a web-building spider

The ideal free distribution (IFD) model predicts that consumers match the distribution of resources across habitat patches and that this association should lead to equal individual fitness among individuals in a population. Here we studied to what extent predators utilize different prey groups and if the resulting spatial patterns relate to the reproductive success of individuals in a population of a web-building spider species (Phylloneta impressa Theridiidae). Web-building spiders, their prey remains, egg sacs, and spiderlings were collected in a wheat field, and coordinates of web sites were recorded for spatial point pattern analysis using pair and mark correlation functions. Spiders were aggregated in the study area, but only postreproductive females were aggregated over the full range of spatial scales. Web-owners in clusters caught a higher proportion of hemipteran prey than expected by the mean, suggesting that the availability of this prey type contributed to the clustering of individuals and the higher reproductive success of females in clusters. However, 2 abundant prey groups (Syrphidae and Hymenoptera) were not more common than expected by the mean at any distance, and another prey group (Elateridae) was even less common in webs close to each other. At least 2 prey groups (Hemiptera and Elateridae) showed deviations from the assumption of the IFD model that predators in clusters should have similar prey capture success compared to predators that are not located in clusters. Both prey groups include many cereal pest species, and our results suggest that spatially explicit information about prey utilization and predator fitness may contribute to a better understanding of the role of natural enemies in biological control.

Radiation sources supporting the use of natural enemies for biological control of agricultural pests

Augmentative biological control as a component of integrated pest management programmes involves the release of natural enemies of the pest, such as parasitoids and predators. Several potential uses for nuclear techniques have been identified which can benefit such programmes; these benefits include facilitating trade, protecting the environment and increasing the overall efficacy of the programmes. This may involve sterilising feed material, hosts or even the control insects. Radiation is currently the most favoured sterilising agent, although availability and cost of radiation sources are considered as limiting the use of radiation in support of biological control. This paper reviews various radiation sources that may be used for this purpose, including a comparison of several key parameters such as cost estimates of these radiation sources that should assist in making a judicious selection of a suitable irradiator.

TRADE-OFFS, TEMPORAL VARIATION, AND SPECIES COEXISTENCE IN COMMUNITIES WITH INTRAGUILD PREDATION

Intraguild predation/parasitism (IGP: competing species preying on or parasitizing each other) is widespread in nature, but the mechanisms by which intraguild prey and predators coexist remain elusive. Theory predicts that a trade-off between resource competition and IGP should allow local niche partitioning, but such trade-offs are expressed only at intermediate resource productivity and cannot explain observations of stable coexistence at high productivity. Coexistence must therefore involve additional mechanisms beside the trade-off, but very little is known about the operation of such mechanisms in nature. Here I present the first experimental test of multiple coexistence mechanisms in a natural community exhibiting IGP. The results suggest that, when resource productivity constrains the competition-IGP trade-off, a temporal refuge for the intraguild prey can not only promote coexistence, but also change species abundances to a pattern qualitatively different from that expected based on the trade-off or a refuge alone. This is the first empirical study to demonstrate a mechanism for why communities with IGP do not lose species diversity in highly productive environments. These results have implications for diversity maintenance in multi-trophic communities, and the use of multiple natural enemies in biological control.

WHY SHORT‐TERM EXPERIMENTS MAY NOT ALLOW LONG‐TERM PREDICTIONS ABOUT INTRAGUILD PREDATION

Equilibrium models are increasingly employed in applied ecology, but often because of experimental logistics, only short‐term laboratory experiments are performed. Here, we use simple models to examine the management relevance of this disconnection between theory and experiments in communities with intraguild predation (IGP). Equilibrium theory shows that IGP can promote coexistence of competitors on a shared resource. However, adding the intraguild predator can result in higher resource densities than in a system with the intraguild prey alone with its resource. This has important management implications when the shared resource is a pest species whose population is controlled by natural enemies. Our models demonstrate why short‐term experiments and studies ignoring alternate resources may bear no relationship to a system at equilibrium. Short‐term experiments quantifying only attack rates can predict a broad range of outcomes. By ignoring conversion efficiency, consumer longevity, and immigration, short‐term studies may, for example, cause erroneous decisions about the introduction of natural enemies in biological control. Thus, attack rates, conversion efficiencies, and immigration rates must all be quantified for a thorough, long‐term understanding of IGP in field systems.

Predicting Caterpillar Parasitism in Banana Plantations

This paper links ecological theory to the biological control of insect pests in banana plantations. Through an established predictive approach, ecological data on tritrophic interactions from natural systems were used to formulate simple recommendations for biological control in banana plantations. The specific goals were (1) to determine the most effective parasitoid enemies for biological control of lepidopteran larvae in banana plantations and (2) to examine the impact of nematicides on enemy populations. To assess percent parasitism, we reared 1,121 lepidopteran larvae collected from six plantations managed under two nematicide regimens. Attack by parasitoids in the families Tachinidae (Diptera), Braconidae, Eulophidae, and Chalcididae (Hymenoptera) closely paralleled rates reported for species with similar characteristics in lowland wet forests, and statistical models predicted the relative importance of these parasitoids as sources of mortality. We found that tachinid flies were the most important source of early instar larval parasitism in banana plantations, and their importance increased with more intensive nematicide applications. The statistical models that we derived from data on natural systems were useful in predicting which parasitoids would be important in banana and which larval characteristics they would preferentially attack. This approach could be used in other managed ecosystems where the identification of effective biological control agents is needed.

Conservation and enhancement of natural enemies in biological control

Conservation and enhancement of natural enemies in biological control

Evolutionary and Applied Aspects of the Behavioural Ecology of the Stemborer Parasitoid Cotesia Flavipes

Cotesia flavipes (Hymenoptera: Braconidae) is a braconid larval parasitoid that has been used in the biological control of tropical stemborers in gramineous plants. The current research status on the behavioural ecology of this parasitoid is reviewed. The stimuli involved in the location of the host-microhabitat and the behaviour on infested plants and inside stemborer tunnels are discussed. Several aspects of the host foraging behaviour on C. flavipes are discussed in relation to the ecology of the parasitoid, such as the role of learning in foraging and clutch size allocation decisions. Variation in behaviour can be an obstacle in the effective use of natural enemies in biological control. Behavioural variation may exist because individuals differ genetically in their propensity to find or accept different hosts. Individuals may also differ because they have experienced different environments (i.e. learning). The second part of this paper focuses on the intraspecific variability in C. flavipes behaviour and discusses to what extent the reported plant and host specificity in C. flavipes has a genetic basis or is due to phenotypic plasticity through learning.

Novel Associations and Importation Biological Control: The Need for Ecological and Physiological Equivalencies

One tactic of importation of natural enemies for biological control of stemborers and other pests is the use of parasite species that have had no previous association with the pest. This ‘novel association’ approach offers the possibility of using parasites that have proven effective against a stemborer species other than the target stemborer pest. Nevertheless, creation of a novel host-parasite association requires that the novel host be ecologically and physiologically equivalent to the ancestral host. Selecting natural enemies based on ecological and physiological equivalence offers the best possibility of temporal, behavioural, nutritional and immunological compatibility in the host-parasite interaction, and reduces the chances of failure with the imported parasite species.

Observations on Argentine stem weevil mortalities in Volcanic Plateau pastures

Recent research at Ruakura has shown that the negative correlation between Argentine stem weevil (Listronotus bonariensis (Kuschel)) population survival (egg to adult) and egg density was density dependent. Density dependent mortalities could arise from pathogens, predators, parasitoids, larval combat and chemical releases by larvae and/or by the host plant. Large mortalities arising from pathogens, parasitoids, soil invertebrate predators and possibly Carabidae and Staphylinidae predators can be discounted in populations at Wairakei in the central North Island. Even without knowing the causative agent of the population mortality, any considerations for releases of natural enemies for biological control of stem weevil should act to augment this existing control. It is recommended that parasitoids be evaluated for release against late larval instar, pupae and adults.

Evidence for Competitive Exclusion of Introduced Natural Enemies in Biological Control: An Addendum

The direct relationship between cigarette smoking and lung cancer is well known. However, this does not mean that all smokers will necessarily develop lung cancer or that nonsmokers will never contact lung cancer. The same kind of reasoning should be applied to the question of competitive exclusion of introduced natural enemies in biological control. In a previous paper, we established an inverse relationship between (1) the rate of (or percent) establishment of a large group of introduced predators and parasites and (2) the number of exotic incumbent species of natural enemies present and the number released simultaneously (see Ehler and Hall [1982] for details). We noted that the empirical evidence was consistent with the competitive-exclusion hypothesis and that therefore the hypothesis should not be rejected. We did not claim that competitive exclusion has occurred frequently or that our results were conclusive, as some have suggested, and we most certainly did not conclude that all (or most) establishment failures involving multiple-species introductions were due to competitive exclusion. Because too many people have read their own erroneous conclusions into our paper, we feel compelled to set the record straight.

Evidence for Competitive Exclusion of Introduced Natural Enemies in Biological Control

The rates of establishment of exotic natural enemies introduced against exotic pests in the orders Homoptera, Lepidoptera, and Coleoptera were found to be inversely related to (1) the number of species released at a given time and place and (2) the number of exotic incumbent species of natural enemies present. Thus, competitive exclusion of introduced natural enemies has probably occurred and contnbuted to the relatively low rate of establishment in biological control. It is suggested that, in cases in which less-than-complete control was obtamed through multiple-species releases, natural enemies capable of effective control of the target pest may have been competitively excluded. Because of this possibility, use of the empirical approach of releasing all available species of natural enemies, with the hope that the best species or combination of species will be sorted out in the field, should be questioned. In modern biological control, a more rational release strategy is in order.