Studies on exploiting semiochemicals for pest management in organic farming systems OF0188

This study addresses the extent to which pest management systems can exploit semiochemicals (defined below) in ways acceptable to organic farming, and determines where the science base needs to be expanded to accommodate specific problems arising in an increasing organic farming sector. It considers whether current knowledge of semiochemical release from particular crop plants, herbs and wild plant species could be investigated further in relation to organic farming practice and identifies how strategies of multiple cropping, that exploit known semiochemical interactions, could be applied to key pest problems in organic production. Where such exploitation is not feasible, other strategies using semiochemicals including traps, extracts of natural products and nature-identical synthetic products are considered. Finally, general and specific directions in which research and development could facilitate greater penetration of the use of semiochemicals in crop protection for organic farming are identified. Semiochemicals are natural products that, by acting as signals, regulate interactions between organisms e.g. plants and insects. Once the semiochemical interactions between a pest and its host plant have been elucidated they can be exploited to regulate the pest population, providing an alternative control strategy to conventional toxicants. The choice of approach by which the semiochemicals are deployed relates to three options, i.e. from a natural plant source, from an extract or as a nature identical synthetic product. However, even where the most natural situations of mixed cropping are used, the scientific basis of the interaction must be established for robustness and sustainability of the approach. A complete understanding of the process allows a risk assessment to be made of any problems that might ensue when exploiting natural systems in different configurations from those encountered naturally. A major approach to using semiochemical based pest control is to exploit ways of repelling pests from crop plants and attracting them towards trap plantations. Deploying semiochemicals generated naturally by plants is consistent with organic farming practice, where a range of mixed cropping techniques are employed already, which ‘unconsciously’ utilise semiochemical effects. Thus, the acceptance and use of systems exploiting aspects of semiochemical deployment demonstrate an emerging role in organic farming practices. However, as emphasised before, a comprehensive knowledge of the semiochemical interactions that underpin these techniques is vital if they are to be exploited fully. Other pest control approaches compatible with organic farming, such as encouragement of beneficial species and the use of reflective surfaces in mulches, may not involve semiochemical effects, but could be exploited more beneficially by integration with semiochemical practices. Semiochemicals generated naturally by plants can be used to influence beneficial organisms as well as invertebrate pests. For example, plant defence chemicals, induced by pest or pathogen infestation, can affect the behaviour of pests and their natural enemies. Semiochemicals can be employed to maximise the impact of parasitic organisms that attack pest populations, for example in the management of refugia for maintaining and increasing populations of these beneficial organisms. In addition, the approach can be applied against other organisms antagonistic to agriculture besides invertebrate pests, for example in weed control, where signals interfering with weed germination can be exploited. Extracts of natural products provide semiochemicals in a form that is familiar and acceptable to organic farming practice, where plant extracts are already used as toxicants or as semiochemical antifeedants and repellents. However, often the scientific basis for use of these materials is limited, and therefore, exploitation is also limited and can be unreliable. By understanding the composition and the mechanism of activity of semiochemicals, natural product extracts can be improved by selection of the best sources of natural materials and appropriate processes of extraction and formulation. Many natural products, particularly pheromones (semiochemicals acting between members of the same species), can be synthesised as nature-identical and the synthetic forms are often indistinguishable from the natural form. Synthesis can be expensive, but where possible, starting materials should be obtained from natural renewable resources. Nature-identical synthetic pheromones are used widely in parts of the world, either deployed in traps for monitoring, mass trapping and lure and kill strategies or for direct pest control approaches such as mating disruption. In addition, manipulation of beneficial species with pheromones is being investigated and synthetic food-related attractants and oviposition attractants have also been developed for pests where pheromones are not available. Already some nature-identical synthetic semiochemicals have been accepted as compatible with organic farming practice. The registration of many sex and aggregation pheromones has been possible because they are nature-identical and are deployed away from the crop or on crop areas that are not consumed. In most cases, semiochemicals, deployed alone, are not sufficiently robust to control pest populations directly. They are most effective when incorporated into strategies, such as the ‘push-pull’ strategy, that are integrated with other forms of pest control, e.g. pathogens, parasitoids and predators, mechanical barriers and resistant plant varieties. The integration of semiochemical approaches with other methods of pest population reduction will help prevent the development of pest resistance to the overall strategy. Since the integrated strategy comprises a number of components that affect different aspects of pest behaviour and development each component can be relatively ineffective when compared to conventional pesticides. However, this has the advantage of not selecting efficiently for resistance to any component of the strategy and thus contributes to the sustainability of the approach. Recommendations 1) Develop a priority list of specific and general problems in organic production to be targeted by semiochemical methodologies in addition to known problems such as in carrot and lettuce production, aphids on a range of vegetable crops and for fruit pests. 2) Develop semiochemical based control methods suitable for 1) and for the targets already known. 3) Provide scientific input, where lacking, for 1 and 2. 4) Encourage greater diversification in organic cropping systems, including agroforestry, so as to exploit current knowledge of semiochemical based control and to pave the way for new interventions as the science develops. 5) Consider semiochemical attributes of non-crop plant inputs including mulches, weeds and multifunctional beneficial plants and the roles that they might play in organic systems. 6) Initiate organic plant breeding programmes, specifically to exploit natural semiochemical release where understood, for crop and companion plants

Management of strawberry blossom weevil and European tarnished plant bug in organic strawberry and raspberry using semiochemical traps

The strawberry blossom weevil (Anthonomus rubi) and the European tarnished plant bug (Lygus rugulipennis) cause large (10 - >80%) losses in yield and quality in organically grown berries. A consortium with 6 European countries has been created to work on the management of those pests. The pheromones of A. rubi and L. rugulipennis have been characterized in England by NRI/EMR. For the attraction of A. rubi the importance of host plant volatiles in combination with the pheromones has also been documented. The natural semiochemical mechanisms of sexual attraction and host plant finding of A. rubi and L. rugulipennis will be further studied and exploited to develop effective semiochemical traps for their management through mass trapping. Attractive lures for these two species will then be combined into a single multitrap with the aim of managing two pests simultaneously in each crop. This will be one of the first approaches to pest management of non-lepidopteran insect pests of horticultural crops using semiochemicals in the EU, and probably the first to target multiple species from different insect orders. The project will be organized in the following work packages; 1) Chemical analysis of plant volatiles, 2) Pest insects in strawberry, 3) Pest insects in raspberry and 4) Trap design and lure development. The authors gratefully acknowledge the financial support for this project provided by the CORE Organic II Funding Bodies, being partners of the FP7 ERA-Net project, CORE Organic II (Coordination of European Transnational Research in Organic Food and Farming systems, project no. 249667)

Management of strawberry blossom weevil and European tarnished plant bug in organic strawberry and raspberry using semiochemical traps

In the absence of effective control measures, the strawberry blossom weevil (Anthonomus rubi), the European tarnished plant bug (Lygus rugulipennis) and the raspberry beetle (Byturus tomentosus) cause large (10 - >80%) losses in yield and quality in organically grown strawberry (A. rubi and L .rugulipennis) and raspberry (A. rubi and B. tomentosus). In this project the natural semiochemical mechanisms of sexual attraction and host plant finding of these key pests will be exploited to develop effective semiochemical traps for their management through mass trapping. Attractive lures will be combined into a single multitrap for economic management of these pests simultaneously in each crop. This will be one of the first approaches to pest management of non-lepidopteran insect pests of horticultural crops using semiochemicals in the EU, and probably the first to target multiple species from different insect orders. Growers of organic raspberry and strawberry crops currently have few options for effective control of these pests and development of semiochemical-based, non-pesticidal management techniques will make a major contribution to reduction of significant economic losses

Evaluation of semiochemical based push-pull strategy for population suppression of ambrosia beetle vectors of laurel wilt disease in avocado.

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae and Platypodinae) bore into tree xylem to complete their life cycle, feeding on symbiotic fungi. Ambrosia beetles are a threat to avocado where they have been found to vector a symbiotic fungus, Raffaelea lauricola, the causal agent of the laurel wilt disease. We assessed the repellency of methyl salicylate and verbenone to two putative laurel wilt vectors in avocado, Xyleborus volvulus (Fabricius) and Xyleborus bispinatus (Eichhoff), under laboratory conditions. Then, we tested the same two chemicals released from SPLAT flowable matrix with and without low-dose ethanol dispensers for manipulation of ambrosia beetle populations occurring in commercial avocado. The potential active space of repellents was assessed by quantifying beetle catch on traps placed 'close' (~5-10 cm) and 'far' (~1-1.5 m) away from repellent dispensers. Ambrosia beetles collected on traps associated with all in-field treatments were identified to species to assess beetle diversity and community variation. Xyleborus volvulus was not repelled by methyl salicylate (MeSA) or verbenone in laboratory assays, while X. bispinatus was repelled by MeSA but not verbenone. Ambrosia beetle trap catches were reduced in the field more when plots were treated with verbenone dispensers (SPLAT) co-deployed with low-dose ethanol dispensers than when treated with verbenone alone. Beetle diversity was highest on traps deployed with low-dose ethanol lures. The repellent treatments and ethanol lures significantly altered the species composition of beetles captured in experiment plots. Our results indicate that verbenone co-deployed with ethanol lures holds potential for manipulating ambrosia beetle vectors via push-pull management in avocado. This tactic could discourage immigration and/or population establishment of ambrosia beetles in commercial avocado and function as an additional tool for management programs of laurel wilt

Disruptant Effects of 4-Allylanisole and Verbenone on \u3ci\u3eTomicus Piniperda\u3c/i\u3e (Coleoptera: Scolytidae) Response to Baited Traps and Logs

We assessed the inhibitory effects of the host compound 4-allylanisole (release rates = 1 and 2 mg/d in 1994, and 1 and 10 mg/d in 2001) on the response of the pine shoot beetle, Tomicus piniperda (L.), adults to funnel traps baited with the attractant host compound α-pinene (release rate = 150 mg/d) in two pine Christmas tree plantations in Michigan in spring 1994 and two other plantations in spring 2001. In three of the four plantations, all doses of 4- allylanisole significantly reduced T. piniperda attraction to α-pinene-baited traps by 46 to 76%. We also tested the inhibitory effect of the antiaggregation pheromone verbenone (release rates = 2 and 4 mg/d) on T. piniperda attack density on pine bolts (average bolt length was 62 cm and diameter was 19 cm) at three sites (two pine forest stands and one Christmas tree plantation) in Michigan in 1994. Verbenone significantly reduced T. piniperda attack density by 37 to 60% at the two pine stands, but not at the Christmas tree plantation

Bark Beetle (Coleoptera: Curculionidae: Scolytinae) Community Structure in Northeastern and Central Minnesota

Large-scale surveys of forest insects provide two distinct benefits: the detection of invasive and exotic species that cause millions of dollars of damage annually to forest and ornamental industries, and the addition of a wealth of species distribution and diversity information to the scientific community. We intensively surveyed the Northeast and East-central regions of Minnesota from 2006-2008 for invasive/exotic and native Scolytinae using Lindgren funnel traps baited with one of four lures (a/β-pinene, ultra-high-release ethanol [EtOH], EtOH+a-pinene, and Ips 3-part). We captured 16,841 scolytines (representing 25 genera) of which over 40% were Ips pini (Say) and Ips grandicollis (Eichhoff). We found two exotic Scolytinae, Scolytus multistriatus (Marsham) and Scolytus schevyrewi Semenov, both of which had previously been recorded in Minnesota. Two native species, Conophthorus coniperda (Schwarz) and Crypturgus pusillus (Gyllenhal), were reported for the first time in Minnesota. Non-metric multi- dimensional scaling and analysis of similarities indicate that lure types capture different Scolytinae communities, while year, weather pattern and region factors were not significant. We also report the seasonal phenology of the seven most abundantly captured species; Dendroctonus valens LeConte, Hylastes porculus Erichson, Hylurgops rugipennis pinifex (Fitch),I. grandicollis, I. pini, Orthotomicus caelatus (Eichhoff) and Pityophthorus spp. Eichhoff

Systemic and sex-biased regulation of OBP expression under semiochemical stimuli.

Abstract Constitutive expression of Odorant-Binding Proteins (OBPs) in antennae and other body parts has been examined mainly to infer their involvement in insect olfaction, while their regulation in response to semiochemical stimuli has remained poorly known. Previous studies of semiochemical response were basically done using electrophysiology, which integrates the response of the set of OBPs present in an antenna or sensillum, without revealing the regulation of OBPs or which ones might be involved. In this study we used boll weevil as a model and mined its OBPs by RNA-Seq to study their simultaneous antennal expression by qPCR under controlled semiochemical stimuli with aggregation pheromone and plant volatiles. In the absence of a semiochemical stimulus, 23 of 24 OBPs were constitutively expressed in the antenna in both sexes. Semiochemicals changed systemically the expression of OBPs in both sexes. There were different patterns of up- and down-regulation in female antennae for each semiochemical stimulus, consistent with female chemical ecology. On the other hand, the only response in males was down-regulation of some OBPs. We suggest that these systemic changes in OBP expression might be related to enhancing detection of the semiochemical stimuli and/or priming the olfactory system to detect other environmental chemicals

Egg parasitoid exploitation of plant volatiles induced by single or concurrent attack of a zoophytophagous predator and an invasive phytophagous pest

Zoophytophagous insect predators can induce physiological responses in plants by activating defence signalling pathways, but whether plants can respond to facultative phytophagy by recruiting natural enemies remains to be investigated. In Y-tube olfactometer bioassays, using a system including a Vicia faba plant, the zoophytophagous predator Podisus maculiventris and the egg parasitoid Telenomus podisi, we first demonstrated that T. podisi females are attracted by broad bean plants damaged by feeding activity of P. maculiventris and on which host egg masses had been laid, while they are not attracted by undamaged plants or plants damaged by feeding activity alone. In a second experiment, we evaluated the impact of the invasive phytophagous pest Halyomorpha halys on this plant volatile-mediated tritrophic communication. Results showed that the invasive herbivorous adults do not induce plants to recruit the native egg parasitoid, but they can disrupt the local infochemical network. In fact, T. podisi females are not attracted by volatiles emitted by plants damaged by H. halys feeding alone or combined with oviposition activity, nor are they attracted by plants concurrently infested by P. maculiventris and H. halys, indicating the specificity in the parasitoid response and the ability of the invasive herbivore in interrupting the semiochemical communication between plants and native egg parasitoids. To the best of our knowledge, this is the first study showing that zoophytophagous predator attacks induce indirect plant defences similarly to those defence strategies adopted by plants as a consequence of single or concurrent infestations of herbivorous insects

Examining the role of individual movement in promoting coexistence in a spatially explicit prisoner's dilemma

AEFB gratefully acknowledges the support of an EPSRC CASE PhD studentship.The emergence of cooperation is a major conundrum of evolutionary biology. To unravel this evolutionary riddle, several models have been developed within the theoretical framework of spatial game theory, focussing on the interactions between two general classes of player, "cooperators" and "defectors". Generally, explicit movement in the spatial domain is not considered in these models, with strategies moving via imitation or through colonisation of neighbouring sites. We present here a spatially explicit stochastic individual-based model in which pure cooperators and defectors undergo random motion via diffusion and also chemotaxis guided by the gradient of a semiochemical. Individual movement rules are derived from an underlying system of reaction-diffusion-taxis partial differential equations which describes the dynamics of the local number of individuals and the concentration of the semiochemical. Local interactions are governed by the payoff matrix of the classical prisoner's dilemma, and accumulated payoffs are translated into offspring. We investigate the cases of both synchronous and non-synchronous generations. Focussing on an ecological scenario where defectors are parasitic on cooperators, we find that random motion and semiochemical sensing bring about self-generated patterns in which resident cooperators and parasitic defectors can coexist in proportions that fluctuate about non-zero values. Remarkably, coexistence emerges as a genuine consequence of the natural tendency of cooperators to aggregate into clusters, without the need for them to find physical shelter or outrun the parasitic defectors. This provides further evidence that spatial clustering enhances the benefits of mutual cooperation and plays a crucial role in preserving cooperative behaviours.PostprintPeer reviewe