Keywords

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2.1 Introduction

The concept of integrated pest management (IPM) is an ecosystem approach to crop production and protection that combines different management strategies and practices to grow healthy crops and minimize the use of pesticides. Pests in cultivated crops include pest animals (including arthropods, mollusks, nematodes, and vertebrates), plant pathogens (viruses, bacteria including phytoplasmas and Liberibacter, fungi), and weeds. IPM aims to suppress pest populations below a specific economic injury level (EIL). The EIL is defined as “The lowest population density of a pest that will cause economic damage; or the amount of pest injury which will justify the cost of control” (Stern et al. 1959). Regarding IPM, currently 67 different definitions are available in the worldwide literature. The Food and Agriculture Organization of the United Nations (FAO), e.g., defines IPM as follows: “Integrated Pest Management means the careful consideration of all available pest control techniques and subsequent integration of appropriate measures that discourage the development of pest populations and keep pesticides and other interventions to levels that are economically justified and reduce or minimize risks to human health and the environment. IPM emphasizes the growth of a healthy crop with the least possible disruption to agro-ecosystems and encourages natural pest control mechanisms” (FAO 2015). The International Organization for Biological and Integrated Control-West Palearctic Regional Section (IOBC-WPRS) defines further the concept of integrated production (IP). It is a concept of sustainable agriculture developed in 1976 which has gained international recognition and application. The concept is based on the use of natural resources and regulating mechanisms to replace potentially polluting inputs. The agronomic preventive measures and biological/ physical/chemical methods are carefully selected and balanced taking into account the protection of the environment and the health of farmers and consumers (Boller et al. 2004). The 2004 IOBC Standard for Integrated Production covers ecological, ethical, and social aspects of agricultural production as well as aspects of food quality and safety. The current set of IP guidelines and related tools has proven helpful and inspirational for farmers’ organizations looking for a feasible way to work with integrated production in the premium food segment (Boller et al. 2004).

2.2 Regulation of IPM in Europe

IPM in Europe is regulated in Directive 2009/128/EC. A definition similar to the definition published by the FAO is provided by the European Union Framework Directive on the sustainable use of pesticides in Art. 3 No. 6: “Integrated pest management” means careful consideration of all available plant protection methods and subsequent integration of appropriate measures that discourage the development of populations of harmful organisms and keep the use of plant protection products and other forms of intervention to levels that are economically and ecologically justified and reduce or minimize risks to human health and the environment. “Integrated pest management” emphasizes the growth of a healthy crop with the least possible disruption to agroecosystems and encourages natural pest control mechanisms” (Directive 2009/128/EC). The general principles are published in Annex III of Directive 2009/128/EC. Establishing incentives for professionals to implement guidelines for IPM can be found in Art. 14 No. 5 and the obligation of EU-ME to report how to ensure the general principles of IPM in Art. 14 No. 4: Member states shall describe in their national action plans (NAP) how they ensure that the general principles of integrated pest management as set out in Annex III are implemented by all professional users by 1 January 2014. Thus, all 27 member states of the European Union are to transpose this directive into national legislation.

The EU Framework Directive requires that all EU member states develop an NAP, which ensures that a set of eight general principles (Fig. 2.1) of IPM (Annex III) are implemented by all professional pesticide users compulsory from 1 January 2014 (European Union 2009):

Fig. 2.1
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The set of eight general principles of IPM

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  1. 1.

    Prevention and suppression of harmful organisms

  2. 2.

    Monitoring, warning, forecasting, and the use of advice

  3. 3.

    Decision-making (e.g., threshold values)

  4. 4.

    Preference of nonchemical methods

  5. 5.

    Pesticide selection (least side effects)

  6. 6.

    Necessary level (reduced pesticide use)

  7. 7.

    Anti-resistance strategy

  8. 8.

    Documentation and assessment

Member states shall establish appropriate incentives to encourage professional users to implement crop- or sector-specific guidelines for integrated pest management on a voluntary basis. Public authorities and/or organizations representing particular professional users may draw up such guidelines. Member states shall refer to those guidelines that they consider relevant and appropriate in their NAPs (Directive 2009/128/EC, Art 14 No. 5).

In Germany, guidelines (cultural or sector-related production) are developed through associations of farmers, gardeners, and associations with scientific support under a strong consideration of practical relevance. The Integrated Production Commission of the IOBC-WPRS, e.g., elaborates crop-specific guidelines for integrated production of agricultural crops that have formed the basis for IPM programs in Switzerland, the Czech Republic, and Italy. Further, it develops and standardizes methods of testing effects of pesticides on beneficial organisms. In the fulfillment of its objectives, it collaborates with other international organizations, notably FAO, WHO, the Commission of the European Union (CEU), and the European Plant Protection Organization (EPPO). The IOBC-WPRS has already published crop-specific IP guidelines for a large number of crops (pome fruits, stone fruits, arable crops, grapes, soft fruits (berries), olives, citrus, and field grown vegetables). Further guidelines have to be developed for sugar beet (Gummert et al. 2012), wine growing, urban greening, etc. Up to 2018, guidelines should be available in every plant production system including minor crops (mostly vegetables, fruits, nursery stock, and ornamentals). At present, around 30 % of farmers observe guidelines 3 years after their establishment.

The guidelines must include the following topics:

  1. 1.

    Prevention: crop rotation, cultivation (non-plow tillage), resistance, etc.

  2. 2.

    Observation: the use of learned lessons

  3. 3.

    Decision: check of pest development and thresholds

  4. 4.

    Preference of nonchemical methods: biotechnical, physical, and technical methods, biologicals, etc.

  5. 5.

    Pesticide: specific, environmental, reduced dose, and necessary level

  6. 6.

    Documentation and control of results

For minor crops, sustainability can only be realized by the continued availability of crop protection solutions for pest control. Since the last decade, European farmers have far less new technology to drive agricultural production than their competitors in other regions of the world. In Europe, particularly the number of minor crops without viable solutions for plant protection has increased (Lamichhane et al. 2015). This is mainly because many effective compounds once registered on an EU level have not been reauthorized due to stricter regulation processes. The limited range of available pesticides has increased the risk of pesticide resistance development since, in the absence of several pesticides with various modes of action, farmers must apply only a narrow spectrum of active ingredients (Lamichhane et al. 2015). Research and development (R&D) for new crop protection products needed by European farmers is in decline, according to an analysis of market trends in the EU and around the world. A recent study reveals that the number of active ingredients being developed and introduced in the EU is steadily decreasing – even as global expenditure on agricultural R&D is on the rise (Anonymous 2013). The share of global crop protection R&D focused on European markets has decreased from 33 % in the 1980s to only 16 % today. Moreover, the European market’s share of total worldwide R&D expenditure for new product development in agricultural life sciences is just 7.7 % today compared to 33 % in the 1980s (Anonymous 2013). The most important reasons behind the reduction in R&D investment in crop protection products for the European market are the nonacceptance of GMOs and the harsh regulatory environment. Thus, the future development and implementation of innovative IPM solutions are very important.

2.3 Demonstration Farms for IPM in Germany

In the year 2007, the network of reference farms, called “Demonstration Farms for Integrated Plant Protection” (DF-IPP), an important component of the NAP in Germany, has been started. It is a joint project of the Federal Ministry of Food and Agriculture of Germany (BMEL), the plant protection services in the federal states and the Julius Kühn-Institut, Federal Research Centre for Cultivated Plants (JKI). The network focuses on surveying representative farms to demonstrate the feasibility of IPM in representative regions and crops and to obtain annual data on plant protection product (PPP) uses in major crops and to generate additional information relevant to crop protection. All PPP treatments are evaluated to determine their actual use intensities based on the so-called treatment frequency index (TFI) and the necessary minimum of PPP use, as determined by experts from the plant protection services (Hommel et al. 2014). Various checklists were developed to evaluate the implementation of IPM on demonstration farms (Peters et al. 2015). The following parameters are used to explain differences in TFI scores between farms, within or between regions: field and farm size, soil quality, previous crop, tillage, sowing date, cultivar resistance, and the use of decision support systems (Hommel et al. 2014). The data are pooled for four selected regions (north, east, south, and west) and for Germany in total. In arable farming, e.g., about 75 farms are surveyed annually. Integrated plant protection (IPP) guidelines are to be applied in the model and demonstration project DF-IPP (Hommel et al. 2014). Thus, new developments and innovative strategies for sustainable plant protection can easily be implemented in practice and according to a circle of measurements and assessments (Fig. 2.1) under practical conditions evaluated (Gündermann 2014). The outcome of the IPM measures and assessments will be communicated to farmers and public (Fig. 2.2).

Fig. 2.2
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The circle of measurements and assessments on DF-IPP in Germany (Gündermann 2014)

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2.4 Certification of Plant Protection Knowledge

Professional users of PPPs must be certified (plant protection certification) to use plant protection products. Undergoing training in handling and using plant protection products, related to the certification, is voluntary in all member states. The state certificate includes a written and oral exam or an approved associated degree. Independent training and advice for farmers are regulated by the national plant protection acts and accompanied regulations, such as the regulation on professional knowledge. In Germany, e.g., each of the 16 federal states is responsible for advice, awareness raising, and training, in particular on good plant protection practice including IPP and the implementation of NAP measures (Hommel et al. 2014). The federal states are also required to diagnose and monitor pests, carry out field experiments and PPPs trials, and maintain databases and forecasting platforms in the Internet. The German Internet platform ISIP (Information System for Integrated Plant Production: www.isip.de) integrates weather data in disease models and provides regional decision support in major crops (Racca et al. 2011). In Denmark, an extensive monitoring system is operating linked to the farm advisory system, which has a high impact on reduced pesticide uses (Kudsk and Jensen 2014). In Germany, the organization of public extension differs from state to state (Hommel et al. 2014). Very common schemes to distribute knowledge are training courses in winter time and open field days during the growing season. During the latter, information is mainly transmitted via online portals, monitoring systems, prognosis models, and specific decision support systems (DSS) (Hommel et al. 2014). Professional users, advisors in plant protection, and distributors of PPPs have to renew their certification every 3 years. In Germany, training details and education topics have to be specified by region and crop through the responsible authorities (Freier and Zornbach 2008).

2.5 Development of Innovative Plant Protection Strategies

The future of agricultural plant production is threatened by the emergence of pest resistance and a declining availability of active substances in plant protection products (Lamichhane et al. 2015). Additionally, invasive species like the brown marmorated stink bug (Halyomorpha halys) (Leskey et al. 2012) and the spotted wing drosophila (Drosophila suzukii) are expanding their native range to other continents (Cini et al. 2014; Vogt et al. 2012). Thus, the numbers of severe agricultural pests registered in pest information databases like the “Pest Information Wiki” (PestinfoWiki Contributors 2015) are increasing continuously. In conclusion, there is a need to design cropping systems less dependent on synthetic pesticides, which integrate innovative plant protection strategies (Barzman et al. 2014). According to the eight principles of IPM formulated in Annex III of Directive 2009/128/EC, we give in the following an overview on important examples for new developments and attempts in plant protection.

2.5.1 Selective and Biorational Pesticides

Pesticides applied on crops shall be as specific as possible for the target pest and shall have the least side effects on human health, nontarget organisms, and the environment (Principle 5 of IPM – pesticide selection). Thus, those insecticides that are efficacious against target pests but less detrimental to beneficials, the so-called biorational pesticides, should be the first choice in IPM programs. This term describes any type of insecticide including botanicals and microbials active against pest populations but relatively innocuous to nontarget organisms and therefore nondisruptive to biological control (Schuster and Stansly 2015). Applied separately, biorational pesticides may perform with less biocidal power and appear more costly than conventional synthetic pesticides. By integrating several alternative methods, they may generate synergies resulting in satisfactory pest control (Barzman et al. 2015). In Chaps. 5 and 8 of this book, examples will be presented dealing with this aspect (Wise 2016; Akhatar and Isman 2016).

2.5.2 Anti-resistance Strategies

Where the risk of resistance against a plant protection measure is known and where the level of harmful organisms requires repeated application of pesticides to the crops, available anti-resistance strategies should be applied to maintain the effectiveness of the products. This should include the use of or rotation of multiple pesticides with different modes of action (Barzman et al. 2015) (Priciple 7 of IPM – anti-resistance strategies). Some studies on this important principle are given in Chaps. 11, 12, 13, 14, 15, and 16 of this book.

2.5.3 Monitoring of Pest Insects by Semiochemicals

Harmful organisms must be monitored by adequate methods and tools. Such adequate tools should include trappings and observations in the field as well as scientifically sound warning, forecasting, and early diagnosis systems, where feasible, as well as the use of advice from professionally qualified advisors (Barzman et al. 2015) (Principle 2 of IPM – monitoring). IPM strategies require a full understanding of the biology and life history of a pest organism and its natural enemies within any ecosystem (Dent 1991). While the adult life stage will be the target for monitoring of pest insects by semiochemicals regularly, in some cases, other ontogenetic stages could be the target of monitoring depending of their biology and ecology. For monitoring of, e.g., mosquito populations, so-called ovitraps mimicking their preferred breeding sites were developed acting as an early warning signal by counting the eggs to preempt any impending dengue outbreaks (Jacob and Bevier 1969). Also in moth control, the monitoring of caterpillars or eggs could be easier than very mobile adult stages (see below). For innovative monitoring methods, which use semiochemicals for luring different life stages of target insects, only adult and egg monitoring are appropriate because no methods exist for luring relative immobile larval stages by chemical components in traps, while the mating and egg laying behavior of adult insects could be much better exploited for the development of chemically lured monitoring traps.

2.5.3.1 Adult Monitoring

Traps consisting of sticky foils or filled with toxic fluids are often equipped with artificial dispensers emitting synthetic sexual pheromones. They are widely used for monitoring the population dynamics of insect pests, which is the basis for decisions regarding chemical control and for calculating the optimal timing for spraying insecticides. Many insect pheromones have been identified in the past and are commercially available today for trapping moths, beetles, flies, and many other pest insects. The Internet database “Pherobase” lists hundreds of sexual pheromones for monitoring purposes (El Sayed 2014), and many of them are today commercially available. Traps equipped with these species-specific lures have allowed for significant advancement of IPM decision-making. However, they also have some weaknesses: the amount of caught specimen is not only influenced by population densities but also by weather conditions, dispenser specifications, and the actual reach of attractive plumes from traps (Miller et al. 2015). Finally, they have to compete against the natural sources of pheromones, mainly female insects themselves, as male-produced pheromones are very rare (Gross 2013). Key parameters influencing the number of trapped organisms from any specified distance of origin from the trap are the probabilities that the trap is found (findability) and that the organism is captured after arriving at the trap (efficiency) and retained (retention) until the trap is emptied by the farmer (Miller et al. 2015).

Besides pheromones, also allelochemicals can be used as lures in traps. Recently, new findings have been reported for psyllids, which could be used for the development of new chemically lured traps for monitoring and also mass trapping (Mayer et al. 2008a, b, 2009, 2011; Rid et al. 2016). In this case, also compounds with a high specificity for the target pest should be used to reduce bycatches of beneficial insects (Weintraub and Gross 2013). The emission rates of the attractive compounds, often plant-produced kairomones, have to be multiple times higher than by using pheromones.

2.5.3.2 Egg Monitoring

Even though in most cases eggs are more difficult to monitor in the field than adults, the advantage of monitoring the egg stage is established in systems, in which robust degree-day models exist for the period of time for egg development, before the damaging larval stage begins. The use of egg traps, e.g., equipped with kairomones from almond, is common and recommended in IPM for monitoring the navel orangeworm (Amyelois transitella) in the USA and Mexico (Anonymous 2002). This method is applied to determine when navel orangeworm eggs will hatch in relation to hull split of infested almonds so a chemical treatment can be timed precisely (Anonymous 2002). The European grapevine moth Lobesia botrana and European grape-berry moth Eupoecilia ambiguella (Lepidoptera: Tortricidae) are the most damaging insect pests in European viticulture. Larvae injure fructiferous organs by feeding and thus promote infestation with bacteria and fungi, such as gray mold Botrytis cinerea. To achieve effective chemical control, insecticide treatments have to be conducted before hatching of the larvae. For this purpose, an egg monitoring is necessary but not practicable. To prevent immoderate insecticide application, which would not be in compliance to IPM, a decision support system for growers is needed, which enables the timing and necessity of pest control. Such a tool, called “moth oviposition card” (M-OVICARD) consisting of volatile and nonvolatile compounds, supported by visual and tactile cues, is currently under development (Greif et al. 2015). The number of eggs, deposited on such a monitoring card, should correlate with actual pest infestation in grape vines and may help to determine the perfect spraying time, resulting in a reduced amount of applied insecticides (Greif et al. 2015).

2.5.4 Nonchemical Methods

Sustainable biological, biotechnical, physical, and other nonchemical methods must be preferred to chemical methods if they provide satisfactory pest control (Principle 4 of IPM – nonchemical methods) (Barzman et al. 2015). Plant protection strategies based on olfactory, gustatory, or acoustic signals are very divers and have a high potential to improve existing IPM strategies. For instance, there are many possibilities for the integration of semiochemical use in IPM strategies. Infochemicals convey information in interactions between individuals, leading in the receiver to a behavioral or physiological response. We distinguish between pheromones, which mediate interactions between organisms of the same species, and allelochemicals, which mediate interactions between two individuals that belong to different species (Dicke and Sabelis 1988). In most cases of pest control, pheromones are used due to their high species specificity. Sex pheromones are both used for monitoring of pest insects and for disturbing mating behavior (Gross 2013; Harari 2016, Chap. 6). Aggregation pheromones can be used for mass trapping, but this type of pheromone occurs only in a few known species (Gross 2013). For the so-called attract-and-kill or lure-and-kill systems, an attractive compound (a pheromone or a kairomone) is combined with a toxic component, like an insecticide or pathogenic microorganism. Ultimately, the potential of infochemicals for plant protection can be used in complex push-and-pull strategies.

2.5.4.1 Mating Disruption by Semiochemicals

The most prominent and environmentally friendly application method for pheromones in plant protection is the mating disruption technique. Females emit an airborne trail of sex pheromones, the so-called pheromone plume, which may be used by males to locate them. This technique exploits the male insects’ natural response to follow the corresponding plume by introducing artificial dispensers emitting synthetic pheromones into their habitat. The synthetic pheromone is a volatile organic chemical designed to mimic the species-specific sex pheromone produced by the female insect. It is important to divide between competitive and noncompetitive mating disruption (Miller et al. 2015). Under competitive attraction operating in a crop treated with multiple point dispensers of synthetic pheromone, the frequency with which males find calling females is reduced because males are diverted from orienting to females or traps due to preoccupation with more numerous nearby dispensers that first attract responders and then arrest and possibly deactivate them (Miller et al. 2010). In contrast, noncompetitive disruption includes masking of females by pheromone dispensers and desensitization of responder sensory systems without first requiring attraction (Miller et al. 2010). Consequently, the male population experiences a reduced probability of successfully locating and mating with females, which can lead to termination of breeding followed by the collapse of insect infestation (Witzgall et al. 2010). The Internet database “Pherobase” currently lists 149 species, for which mating disruption techniques have been proven, and 133 of these are Lepidoptera (El Sayed 2014). To date, important successes include codling moth Cydia pomonella in pome fruit, oriental fruit moth Grapholita molesta in peaches and nectarines, tomato pinworm Keiferia lycopersicella in vegetables, pink bollworm Pectinophora gossypiella in cotton (Welter et al. 2005), and omnivorous leafroller Platynota stultana, European grapevine moth L. botrana, and grape-berry moth E. ambiguella in vineyards (Gross 2013; Welter et al. 2005). The use of the mating disruption technique has been explored against stored-product pests such as Plodia interpunctella and Sitotroga cerealella (Fadamiro and Baker 2002). While most successes have been with Lepidoptera, research on stink bugs and beetles showed promising results (McBrien et al. 2002; Millar et al. 2002).

2.5.4.2 Mating Disruption by Substrate Vibrations

Mating disruption is generally based on sex pheromones and allows sustainable pest control resulting in strong reduction of pesticides sprayed (Witzgall et al. 2010). A very original and innovative approach in mating disruption using substrate vibrations was recently published by Eriksson et al. (2012). They applied disruptive acoustic signals (calls from a rival male) to grapevine plants through a supporting wire which decreased the mating frequency of the leafhopper Scaphoideus titanus, significantly. Read more on this new strategy in Chap. 9 of this book (Polajnar et al. 2016). In case that both acoustic and chemical signals are involved in courtship behavior like known from Drosophila (Fabre et al. 2012) or pear psyllids (Eben et al. 2014; Guedot et al. 2009; Lubanga et al. 2014), the acoustic mating disruption system could be supplemented by specific pheromone dispensers.

2.5.4.3 Mass Trapping

For the biological control of species that produce aggregation pheromones, mass trapping systems can be developed. Mass trapping is a direct control strategy, in which large numbers of pests are captured and removed from the system. Excellent results of the mass trapping technique were obtained in Central and South America by using sophisticated pheromone traps emitting male-produced aggregation pheromones of different weevil species, e.g., the West Indian sugarcane weevil, the banana weevil, and the American palm weevil (Giblin-Davis et al. 1996). In oil palm plantations in Central and South America, the palm weevil (Rhynchophorus palmarum) is a vector of the lethal red ring nematode. Today, the principal control method is a pheromone-based mass trapping, using one trap per acre (Oehlschlager et al. 2002). The key biological factors appear to be the relatively long life and slow reproductive rate of the tropical weevils and the fact that the aggregation pheromones attract both sexes. Success is critically dependent on efficient mass trapping to remove weevils faster than they can reproduce (Welter et al. 2005). Although there are only a few examples of this technique with a satisfactory effectiveness in temperate regions, two prominent examples are known from the control of the bark beetle Ips typographus in Europe and the Mountain pine beetle Dendroctonus ponderosae in North America (Witzgall et al. 2010). Allelochemicals like kairomones are less used in mass trapping as pheromones but are sometimes used in combination. A well-known example for an effective kairomone is the pear ester (ethyl (E,Z)-2,4-decadienoate), a characteristic volatile component of ripe pear. This kairomone is an attractant for adult and larval stages of codling moth C. pomonella. Its identification has allowed the development of several new approaches to successful monitoring and mass trapping of this pest (Light et al. 2001; Knight and Light 2001; Knight et al. 2002). In total, 111 compounds are listed in “Pherobase,” which have the potential for mass trapping applications (El Sayed 2014), but only a few are used in today’s pest control strategies.

2.5.4.4 Attract and Kill (Lure and Kill)

Another approach using sex pheromones or other attractive compounds is the attract-and-kill or lure-and-kill method. A viscous paste, gel, or a spray containing an attractant mixed with an insecticide, sterilant, or insect pathogen (e.g., entomopathogenic fungus or granulosis virus) can be distributed as small droplets, dollops, or a film on twigs or leaves of cultivated plants, eliminating individuals that contact the lure. When a female sex pheromone was used as attractant and a contact insecticide as toxin, males are lured to the droplet, try to mate with it and finally get killed (Charmillot et al. 2000). Huang et al. (2013) suggest that an effective attract-and-kill device should keep target insects from contacting the pheromone source directly to avoid desensitization of the olfactory apparatus, while providing a surface that allows them sufficient time to contact the toxicant and acquire a lethal dosage. Conventional attract-and-kill formulations in which sex pheromones are mixed with an insecticide would discourage moths contacting the insecticide surface for prolonged times. Thus, the better approach would be to spatially separate the sex pheromone or another desensitizing attractant from the toxicant (Huang et al. 2013). A newly developed prototype device for the control of the oriental fruit moth G. molesta was reported recently: It consisted of a fabric pouch that was impregnated with a contact insecticide and baited with a separate female sex pheromone lure, which was placed inside the pouch (Huang et al. 2015). This construction provided a large insecticide-treated surface for males to interact with but also prevented them from directly contacting the attractant for minimizing the risk of moths overloading their sensory system with sex pheromones (Huang et al. 2015). In other cases, an insect could be lured by a plant kairomone like pear ester and killed by an insecticide or granulosis virus after feeding on the droplet (Light 2007). Many limitations of mass trapping by aggregation pheromones also apply to attract-and-kill strategies that target males only. Depending on how the system is implemented, it may also interfere with the male’s location of females through false-trail following, as well as the primary effect of the male’s attraction to insecticide-laced baits (Welter et al. 2005). In total, 35 allelochemicals are listed in “Pherobase,” which have the potential as new lures in attract-and-kill applications (El Sayed 2014). In conclusion, the attract-and-kill technique is a promising approach for IPM, but all knowledge on the biology and behavior of the target pest organisms must be included in the development of more efficient devices (Huang et al. 2013).

2.5.4.5 Repellents, Antifeedants, and Deterrents

There are actually rare examples for the use of repellent components in pest control. Some products containing repellent components, which produce a displeasing smell for mammals like deers, rodents, or wild boar, are commercially available. Throughout the sub-Saharan African countries, in which populations of the African elephant (Loxodonta africana) exist, farmers come into conflict with these pachyderms. Attracted by nutritious crops on the fields, they destroy substantial amounts of harvest by crossing through the plantations and feeding on the crops. As this species is protected and listed as a threatened species by the IUCN Red List and therefore must not be killed (Blanc 2008), new ways need to be found to repel or at least not attract the pachyderms to fields. It was shown recently that garlic, ginger, and lemon grass, plants which contain higher amounts of secondary plant products, were less attractive to elephants than maize (Gross et al. 2016). However, they may not be completely unpalatable or even repellent to them, but their activity could cause an avoidance behavior, which terms the active compound an antifeedant. The selection of appropriate, less attractive, or even unpalatable crops might be a solution for the agricultural sector in or close to elephant dwelled habitats to tackle these conflicts (Gross et al. 2016).

For the control of insect pests, both in greenhouse or field, no repellents have been approved so far worldwide. But there are some research activities trying to develop oviposition deterrents, e.g., for the invasive pest D. suzukii in the field (Stensmyr et al. 2012; Wallingford et al. 2015). The alcohols geosmin and 1-octen-3-ol were found to be deterrent to females of D. suzukii in laboratory choice tests (Wallingford et al. 2015). Furthermore, field experiments revealed that fewer eggs were observed in fruits at harvest and fewer adult D. suzukii were reared from fruits associated with 1-octen-3-ol odors than control fruit of cultivated red raspberry (Wallingford et al. 2015). In other cases, repellents are combined with attractants to so-called push-and-pull strategies (see below).

2.5.4.6 Push-and-Pull Strategies

More complex approaches for using the potential of allelochemicals in plant protection are the so-called push-and-pull strategies (Khan et al. 2010). They consist of cropping systems, in which specifically chosen companion plants are grown in between and around the main crop. Some of these companion plants (intercrop) release infochemicals that repel insect pests from the main crop (“push” component). Furthermore, crops which attract insect pests more strongly than the main crop are planted in its surroundings (“pull” component) (Cook et al. 2007). Future directions for improving existing push-and-pull strategies or the development of new techniques may also include biotechnical applications consisting of artificial dispensers emitting synthetic repellent compounds and traps supplied with synthetic attractants.

2.6 Conclusion

As the R&D for new chemical pesticides needed by European farmers is in decline, the resulting limited range of available pesticides has increased the risk of pesticide resistance development (Lamichhane et al. 2015). Thus, new attempts in the development of nonchemical methods for plant protection in IPM will help to enhance sustainable control of pest organisms and to reduce the amount of applied pesticides. The likeliness of successful pest control will be improved by a combination of different techniques using volatile chemicals for monitoring and semiochemicals as well as vibrational signals for direct control of pest organisms together with a controlled application of biorational or synthetic pesticides. Last but not least, by integrating also functional ecology aspects in IPM strategies like the impact of “ecosystem services” (Wise and Whalon 2009) delivered by native pollinators and pest organisms’ natural enemies (pathogens, predators, parasitoids) will be the way leading to a sustainable agricultural crop production in the twenty-first century.