Interactions Between Entomopathogenic Fungi and Other Natural Enemies: Implications for Biological Control

Pathogens and arthropod natural enemies may contribute to the suppression of insect pest populations either as individual species or as species complexes. However, because natural enemies of insects have evolved and function in a multitrophic context it is important to assess interactions within complexes of natural enemies if they are to be exploited effectively in pest management. Natural enemies can interact either synergistically/additively (e.g. enhanced transmission and dispersal of insect pathogens) or antagonistically (e.g. parasitism/infection, predation and competition). In this paper, studies assessing the potential interactions between insect and fungal natural enemies are reviewed. In general, these studies indicate the positive nature of the interactions between arthropod natural enemies and fungal pathogens with respect to the control of insect populations. More work is required to investigate further the many ways in which the natural enemy community interacts in the agroecosystem     

Using optimality models to improve the efficacy of parasitoids in biological control programmes

Biological control of insect pests relies on the ability of natural enemies to limit pest populations. The behaviours expressed by natural enemies against their prey or hosts are modulated by a number of factors and a better understanding of these factors is key to obtaining more efficacious pest control. We propose here that optimality models based upon a behavioural ecology approach can provide a framework that should enable optimisation of biological control practices. We limit our discussion to parasitoid natural enemies and review the factors known to influence the behaviour of these insects. The most important areas that have been studied extensively in the behavioural ecology of insect parasitoids are addressed here: (1) residence time in a host patch, (2) clutch size, (3) sex ratio, (4) host and patch marking, and (5) diet choice. We discuss the implications of the incorporation of these optimality models into efficacious biological control practices and suggest areas where a better knowledge of the behavioural ecology of these insects could improve the efficacy of parasitoid‐based pest control.     

Use of stable carbon and nitrogen isotopes in insect trophic ecology

Insects are the most diverse organisms and often the most abundant animals in some ecosystems. Despite the importance of their functional roles and of the knowledge for conservation, the trophic ecology of many insect species is not fully understood. In this review, I present how stable carbon (C) and nitrogen (N) isotopes have been used to reveal the trophic ecology of insects over the last 30 years. The isotopic studies on insects have used differences in C isotope ratios between C₃ and C₄ plants, along vertical profiles of temperate and tropical forest stands, and between terrestrial and aquatic resources. These differences enable exploration of the relative importance of the food resources, as well as movement and dispersal of insects across habitats. The ¹³C‐enrichment (approximately 3‰) caused by saprotrophic fungi can allow the estimation of the importance of fungi in insect diets. Stable N isotopes have revealed food resource partitioning across diverse insect species above and belowground. Detritivorous insects often show a large trophic enrichment in ¹³C (up to 3‰) and ¹⁵N (up to 10‰) relative to the food substrates, soil organic matter. These values are greater than those commonly used for estimation of trophic level. This enrichment likely reflects the prevalence of soil microbial processes, such as fungal development and humification, influencing the isotopic signatures of diets in detritivores. Isotope analysis can become an essential tool in the exploration of insect trophic ecology in terms of biogeochemical C and N cycles, including trophic interactions, plant physiological and soil microbial processes.     

Influence of the public's perception,attitudes, and knowledge on the implementation of integrated pest management for household insect pests

Households are mini‐ecosystems that provide a variety of conditions in which a variety of insect species can develop. Whether these insects are considered pests, largely depends on the perception, attitudes, and knowledge of the human inhabitants of the house. If considered unacceptable, residents can attempt to manage the insects themselves, or hire a professional. A pest management professional can provide a quick‐fix solution, often relying on the sole use of insecticides, or a sustainable solution through integrated pest management (IPM). In this review, it is discussed how the public's perception, attitudes, and knowledge affect the implementation of IPM in the household through the following steps: inspection, identification, establishment of a threshold level, pest control, and evaluation of effectiveness. Furthermore, recent and novel developments within the fields of inspection, identification, and pest control that allow to address pest infestations more effectively are described and their implementation in the household environment is discussed. In general, pest management in the household environment is reactive instead of pro‐active. The general public lacks the knowledge of the pest insects’ biology to identify the species, perform a proper inspection and identify causes of pest presence, as well as the knowledge of the available tools for monitoring and pest control. The percentage of individuals that seek professional aid in identification and pest control is relatively low. Moreover, the perception of and attitudes towards household insects generally result in low threshold levels. Current developments of methods for monitoring, identification, and control of insect pests in the household environment are promising, such as DNA barcoding, matrix‐assisted laser desorption/ionization time‐of‐flight and RNA interference. Efforts should be strengthened to alter the perception and attitude, and increase the knowledge of the non‐professional stakeholders, so that correct pest management decisions can be taken.     

Insect declines and agroecosystems: does light pollution matter?

Drastic declines in insect populations, ‘Ecological Armageddon’, have recently gained increased attention in the scientific community, and are commonly considered to be the consequence of large‐scale factors such as land‐use changes, use of pesticides, climate change and habitat fragmentation. Artificial light at night (ALAN), a pervasive global change that strongly impacts insects, remains, however, infrequently recognised as a potential contributor to the observed declines. Here, we provide a summary of recent evidence of impacts of ALAN on insects and discuss how these impacts can drive declines in insect populations in light‐polluted areas. ALAN can increase overall environmental pressure on insect populations, and this is particularly important in agroecosystems where insect communities provide important ecosystem services (such as natural pest control, pollination, conservation of soil structure and fertility and nutrient cycling), and are already under considerable environmental pressure. We discuss how changes in insect populations driven by ALAN and ALAN itself may hinder these services to influence crop production and biodiversity in agricultural landscapes. Understanding the contribution of ALAN and other factors to the decline of insects is an important step towards mitigation and the recovery of the insect fauna in our landscapes. In future studies, the role of increased nocturnal illumination also needs to be examined as a possible causal factor of insect declines in the ongoing ‘Ecological Armageddon’, along with the more commonly examined factors. Given the large scale of agricultural land use and the potential of ALAN to indirectly and directly impact crop production and biodiversity, a better understanding of effects of ALAN in agroecosystems is urgently needed.     

Geographic variation in diapause induction: the grape berry moth (Lepidoptera: Tortricidae)

Diapause in insects occurs in response to environmental cues, such as changes in photoperiod, and it is a major adaptation by which insects synchronize their activity with biotic resources and environmental constraints. For multivoltine agricultural insect pests, diapause initiation is an important consideration in management decisions, particularly toward the end of the growing season. The grape berry moth, Paralobesia viteana (Clemens), is the main insect pest affecting viticulture, and this insect responds to postsummer solstice photoperiods to initiate diapause. Because the range of grape berry moth extends from southern Canada to the southern United States, different populations are exposed to different photoperiodic regimes. We quantified the diapause response in grape berry moth populations from Arkansas, Michigan, New York, Pennsylvania, Texas, and Virginia, and observed latitudinal variation in diapause initiation. Populations from Michigan, New York, and Pennsylvania responded significantly different than those from Arkansas, Texas, and Virginia. We also observed, as a consequence of our experiments, that the timing of our laboratory studies influenced grape berry moth's response to photoperiod, ceteris paribus. Experiments that were conducted when grape berry moth would be naturally in diapause resulted in a significant higher proportion of diapausing pupae at photoperiods (i.e., >15 h) that generally do not induce diapause, suggesting that attention should be paid to the timing of behavioral and physiological experiments on insects. This relationship between photoperiod and diapause induction in grape berry moth across geographic regions will provide applicable knowledge to improve pest management decisions.     

Genetics‐based methods for agricultural insect pest management

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