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Indian Journal of Experimental Biology Vol. 54, March 2016, pp. 163-174 Mini Review Oviposition Deterrents in Herbivorous Insects and their potential use in Integrated Pest Management Archana Kumari* & Nutan Kaushik* The Energy and Resources Institute (TERI), New Delhi-110 003, India Received 21 July 2014; Revised 21 May 2015 In the life cycle of insects, oviposition is an important phenomenon, and it is influenced by many intrinsic and extrinsic factors, especially in relation to suitable hosts for completion of their life-cycle. Oviposition deterrents which deter an insect from laying eggs are important in the management of insect pests. Proper understanding of these deterrents shall provide necessary insight into new vistas for Insect Pest Management. Chemicals from plants and insects play an important role in attracting phytophagous insects for selecting host for oviposition. Considerable research has been done on oviposition deterrents and their mode of actions. In the present review, we have consolidated the updated information on this important aspect of insect behavior. Keywords: Biological control, Host, Insect behavior, IPM, Pests Overview and Perspective females finding and selection of a good site for egg- Study of behavior of oviposition of insects and its laying is a challenging task2. More so, as such insects deterrence is one of the major aspects to understand lack parental care and their decisions have far- the ecology and evolution of interactions between reaching consequences for their offspring. Selection insects and plants. Various aspects related to of oviposition site is influenced by pheromones, interactions between host plants and insects such as which possibly will function either as deterrents or the causes of the host specificity, host shifts, stimulating substance in short range. These sympatric speciation, co-evolution, etc., have been the pheromones may also act as insect repellents or major subject of interest among the scientific attractants in long range perception. For finding a community. The discrimination by ovipositing female suitable site for oviposition or finding host for blood insects often provide the initial basis for divergence of feeding insects, they principally use olfactory and insect populations onto different host plant species, visual cues. Different cues exploited by ovipositing and it may drive the evolution of some plant defenses females influenced by varied arena such as habitat, and the origin of the host as well. Factors such as microbes, infusions and plant produced volatiles communicative, genetic and ecological are known to besides egg and larva, influence the oviposition influence the oviposition behavior, preference for behavior. Females of Pieris brassicae detect plants and plant parts for oviposition in particular. conspecific eggs with the help of olfactory as well as Oviposition behavior is that when a number of chemoreceptors3. The target insect pests can be potential host plants are available, a female will lay controlled and monitored by exploring the use of maximum eggs on her most preferred plant species pheromone in integrated pest management strategies. (or habitat or part of plant), lesser number of eggs on Possible role of sex-peptides in oviposition has been her next preferred plant, and so on1. Pheromones indicated by Singh & Singh in Drosophila sp.4. operating oviposition activities in female insects have In this review, we have focused on oviposition been the point of attention in recent past by scientists deterrents from plants and insects which play an working on pheromones. For haematophagous adult important role in cues that inhibit oviposition, and thus in the survival of phytophagous insects. —————— *Correspondence: Behavioral sequence leading to oviposition Phone: +91 11 24682100; 24682111 Ext: 2519 Fax: +91 11 24682144; 24682145 The gravid females follow certain sequence of E-mail: [email protected]; [email protected] events culminating into oviposition. These include: 164 INDIAN J EXP BIOL, MARCH 2016 (i) searching, (ii) orientation, (iii) encounter, (iv) Pheromones convey messages to conspecifics. The landing, (v) surface evaluation, and (vi) acceptance5. physiochemical properties of such pheromones fulfill While searching, orientation and encounter together these requisites. Oviposition deterrent pheromones form initial phase of the behavioral sequence, promote even spatial distribution of eggs in many landing, surface evaluation and acceptance or insect species10 and remain active for days. Their rejection form the final phase. All the stages of the stability, evaporation and degradation vary host finding and acceptance sequence depend on a considerably among insects. wide variety of sensory cues. Most studies in this Oviposition deterrent cues area have focused on visual factors such as shape, size Ovipositing females generally utilize plant volatiles and colour. as cues for orientation to host plants and the After alighting on a plant, surface perception, both subsequent surface evaluation of plants by means of physical and chemical characteristics, gains less or non-volatile secondary metabolites are usually importance in determining the suitability for 6 of great significance in host recognition. Cues from oviposition . The sensory receptors involved are competitive herbivorous insects may already be present on the tarsi, antennae, proboscis and released at the moment of egg-laying. Such ovipositor of insects. They provide necessary inputs oviposition deterrents are known to inform both to the central nervous system (CNS) which decides conspecific females11 as well as individuals of other finally whether to accept or reject the particular site species10,12. However, it is interesting to note that not for oviposition. It involves balancing a number of only the ovipositing females but also larvae that co- positive and negative signals from the plant, and often occur with ovipositing females produce oviposition the insect must respond to non-plant stimuli, such as deterrents13-15. Larvae are reported to contain eggs, other insects, and pheromones. The outcome of oviposition deterrents in their frass16, regurgitate or as host evaluation behavior may depend to a large secretions of their exocrine glands17. Most extent on physiological factors such as age of the lepidopterons appear to be induced to oviposit in female. response to a single host-specific compound. Oviposition deterrents/repellents Conspecific deterrence through visual and chemical cues has been demonstrated for a large number of Oviposition deterrents/repellents are chemicals 18 which prevent insects from egg-laying Oviposition insect species across several orders . Changes in deterrence is common in many insects as an plant chemistry or exposure of chemicals following evolutionary mechanism or tool to reduce/avoid oviposition can also deter conspecific gravid females and may be induced through plant damage or as a subsequent larval competition. Oviposition deterrents 19 can offer a first line of defense against insect pests. response to the egg itself . It is still not clear Recently, Seenivasagan et al.7 have demonstrated the whether the use of such plant derived cues by the influence of insect repellant DEPA on egg retention insect is an adaptive mechanism (i.e. the insect has and oviposition behavior of mosquito vectors viz., evolved to recognize these new plant signals as a cue Aedes aegypti, A. albopictus, Anopheles stephensi and in order to avoid repeated oviposition) or simply an Culex quinquefasciatus. Extracts of non-host plants effect (i.e. the ovipositing insect no longer recognizes have been effective in protecting hitherto susceptible that host as a preferred oviposition site because of the altered chemical profile of the plant). hosts. A search for active plant constituents that cause avoidance of egg-laying has led to discovery of Mechanism of deterrence unacceptable plant species which are closely related Oviposition deterrent plants or non-host plants to preferred species. Recent studies have modify the insect oviposition behavior. Non-host demonstrated that acceptance or rejection of a plant is a plant that the insect does not accept for particular plant by the gravid females for oviposition oviposition or for feeding, whereas the host plant is a is regulated not only by the presence or absence of plant that the insect accepts for oviposition and for oviposition stimulants but also by negative stimuli feeding20. Species specific plant substances evoked by the co-occurring deterrents. inhibiting oviposition play a decisive role in Pheromones related to oviposition and premating determining the host plant range of egg-laying sexual behavior appear to originate from female females. The availability of the host plant leads to accessory glands or the Comstock-Kellogg glands8,9. rejection of other possible hosts or non-hosts as KUMARI & KAUSHIK: OVIPOSITION DETERRENTS IN HERBIVOROUS INSECTS 165 oviposition substrate even if they are suitable for appropriate concentration. This assumption has been larval development. However, in the absence of the supported by the study on various insect species host plant, less preferred host or sometimes non-hosts which indicated that the egg-laying behavior can be which are insufficient for larval development, may disturbed by the presence of various substances acting become the choice for oviposition. In such insects, the as contact chemical inhibitors22. The non-host plant oviposition seems to be directed

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