Effect Of Kairomones Research Articles

Melanotaenia duboulayiInfluence Oviposition Site Selection byCulex annulirostris(Diptera: Culicidae) andAedes notoscriptus(Diptera: Culicidae) but NotCulex quinquefasciatus(Diptera: Culicidae)

Some species of mosquito can detect the presence of larvivorous fish and select against ovipositing in pools supporting them. The effect of kairomones released by the crimson-spotted rainbowfish Melanotaenia duboulayi (Castelnau) on the oviposition behavior of the freshwater mosquitoes Culex annulirostris Skuse, Culex quinquefasciatus Say, and Aedes notoscriptus Skuse was evaluated in both laboratory and outdoor artificial pool experiments. In the laboratory, colony-reared Cx. annulirostris selected against ovipositing in water that had contained M. duboulayi at densities of one fish per 5, 30, 180, and 1,080 liters. In contrast, gravid Ae. notoscriptus showed a preference for water that had contained the highest density of M. duboulayi (1 in 5 liters). Gravid Cx. quinquefasciatus were neither repelled nor attracted to water that had previously contained M. duboulayi. In outdoor artificial pool experiments, wild Cx. annulirostris females selected against ovipositing in pools containing caged M. duboulayi stocked at rates of 1, 4, and 10 g per 1,000 liters. When fish were removed from the pools, the repellent effect persisted for at least 24 h, whereas at the lower stocking rate, an avoidance response was not noted until 48 h after fish were placed in pools. This suggests a volatile substance, however, the exact nature of the kairomone/s has not been identified.

Kairomonal effect of sex pheromone components of two lepidopteran olive pests on Trichogramma wasps

AbstractEgg parasitoids are known to use a wide range of chemicals, emitted by plants, host eggs or adults, for host selection. The effect of the sex pheromone components of the lepidopteran olive pests Prays oleae (Lepidoptera: Yponomeutidae) and Palpita unionalis (Lepidoptera: Pyralidae) was studied under laboratory conditions, on the foraging behaviour of the egg parasitoid Trichogramma oleae (Hymenoptera: Trichogrammatidae). The response of T. oleae wasps to (Z)‐7‐tetradecenal and (E)‐11‐hexadecenal, major sex pheromone components of P. oleae and P. unionalis respectively, depended on the dose of the pheromone used in a Y‐tube olfactometer bioassay. (E)‐11‐hexadecenal elicited maximum attraction (70%) at a dose of 1 μg, while a dose of 100 μg (Z)‐7‐tetradecenal attracted 80% of the tested wasps. (E)‐11‐hexadecenyl acetate, the second sex pheromone component of P. unionalis, and the binary blend of (E)‐11‐hexadecenyl acetate: (E)‐11‐hexadecenal (7:3) were not attractive at these doses. The results of this research are discussed in view that they may be considered as alternatives in the biological control of these pests.

Attachment strength, aggregation and movement of the zebra mussel (Dreissena polymorpha, Bivalvia) in the presence of potential predators

We carried out laboratory experiments to study the behaviour of zebra mussels in the presence of predators with different feeding habits: the roach Rutilus rutilus (an efficient molluscivore), the racer goby Neogobius gymnotrachelus, the crayfish Orconectes limosus (facultative molluscivores), and the perch Perca fluviatilis (prefers other kinds of food). We studied three size (length) classes of mussels: small ( 17mm). We measured attachment strength and numbers of individuals forming aggregations after 6-d exposure to predators, as well as horizontal and vertical distances moved by mussels after 24h of exposure. Attachment strength and tendency to form aggregations of small and medium mussels increased in the presence of roach. Medium mussels exposed to perch were also more strongly attached than those in the control treatment (no predators). Large mussels were unaffected by any predators. Predators did not affect horizontal distances moved by all sizes of mussels. Small individuals exposed to roach reduced their upward movement. In most cases, the lack of responses to perch (a non-molluscivore) ruled out any potential influence of fish movements or faeces upon mussels, suggesting an effect of predator kairomones. The exception was the attachment of medium individuals, which also responded to the presence of perch. In this case, responses to other stimuli, e.g. fish movements, could be involved.

Role of terpenes from aphid‐infested potato on searching and oviposition behavior of Episyrphus balteatus

AbstractTo cope with pathogen and insect attacks, plants develop different mechanisms of defence, in both direct (physical and chemical) and indirect ways (attractive volatiles to entomophagous beneficials). Plants are then able to express traits that facilitate “top‐down” control of pests by attracting herbivore predators. Here we investigate the indirect defence mechanism of potato plants by analyzing the volatile patterns of both healthy and aphid‐infested plants. Important changes in the emitted terpene pattern by the Myzus persicae infested host plant were observed. Using Solid Phase Micro Extraction (SPME) and GC‐MS, the (E)‐β‐farnesene (EBF) appeared to be emitted by aphid‐infested potato and not by healthy plants. To assess the infochemical role of these volatile releases after aphid damage on the aphidophagous predators Episyrphus balteatus, the hoverfly foraging behavior was assessed using the Observer 5.0 software (Noldus, Wageningen, The Netherlands). Aphid‐free potato plants were also used as a control volatile source in the predator behavioral study. While aphid‐infested plants induced efficient searching and acceptation behaviors leading to egg‐laying, no kairomonal effect of healthy potato plants was observed, leading to longer immobility durations and shorter searching periods in the net cage. High oviposition rate of E. balteatus was observed when aphid‐infested potato was used (mean of 48.9 eggs per laying and per female). On the other hand, no egg was produced by the hoverfly on healthy aphid‐free plants. The E. balteatus foraging and reproductive behaviors according to the volatile emission from aphid‐infested plants are discussed in relation to the potential use of active infochemical molecules in integrated aphid pest management.

The Response Specificity of Trichogramma Egg Parasitoids towards Infochemicals during Host Location

Parasitoids are confronted with many different infochemicals of their hosts and food plants during host selection. Here, we investigated the effect of kairomones from the adult host Pieris brassicae and of cues present on Brussels sprout plants infested by P. brassicae eggs on the behavioral response of the egg parasitoid Trichogramma evanescens. Additionally, we tested whether the parasitoid’s acceptance of P. brassicae eggs changes with different host ages. The wasps did not discriminate between olfactory cues from mated and virgin females or between mated females and males of P. brassicae. T. evanescens randomly climbed on the butterflies, showing a phoretic behavior without any preference for a certain sex. The parasitoid was arrested on leaf parts next to 1-day-old host egg masses. This arrestment might be due to cues deposited during oviposition. The wasps parasitized host eggs up to 3 days old equally well. Our results were compared with former studies on responses by T .brassicae showing that T. evanescens makes less use of infochemicals from P. brassicae than T. brassicae.

Effect of host kairomones and oviposition experience on the arrestment behavior of an egg parasitoid

Chemical residues left by walking adults of the southern green stink bug, Nezara viridula (L.) (Heteroptera: Pentatomidae) induce arrestment behavior in the egg parasitoid Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) leading to prolonged periods of walking on contaminated areas and to systematic return to the stimulus after encountering the treatment borders. In this study, we quantified how the hierarchical value of residues from host adults and oviposition experience can influence the arrestment behavior of T. basalis females. Our results showed that: (1) female wasps perceived host residues at different hierarchical levels depending on the host gender, with a clear preference for the chemical residues deposited by host females rather then host males; (2) wasps' arrestment response to chemical residues of host females became weaker when wasps were not rewarded by an oviposition experience, and stronger following successful oviposition; (3) repeated encounters with host male chemical residues, followed or not by oviposition experience, did not cause wasps to change their innate arrestment response; (4) in the unrewarded condition, arrestment responses of wasps varied according to the time elapsed between successive visits to areas contaminated by host females: responses were weak with a short interval (less than 24 h) and stronger with a long interval (more than 72 h), suggesting that this unrewarded experience, i.e. encounter with female traces not followed by host egg location, fade within a few hours. The potential significance of these results to the host location behavior of T. basalis in the field is discussed.

Inter-clonal variation in phototactic behaviour and key life-history traits in a metapopulation of the cyclical parthenogen Daphnia ambigua: the effect of fish kairomones

We quantified genetic variation for ecological relevant traits in the presence and the absence of fish chemicals of eleven Daphnia ambigua clones that were isolated from six interconnected ponds that differed in water transparency. In a cohort life table experiment, we tested whether genetic variation for a set of key life history traits was present among these clones. In addition the phototactic behaviour of these clones cultured in the presence and the absence of fish kairomones was quantified using a biotest. We detected a significant effect of fish kairomones on the phototactic behaviour and a highly significant genetic variation among clones for this trait in D. ambigua clones isolated from ponds in De Maten. Differences in size at maturity among D. ambigua clones in De Maten were highly significant, whereas differences in spina length among D. ambigua clones in De Maten were not significant. The presence of fish chemicals did not affect the studied life-history traits. We observed a significant positive relationship between average phototactic behaviour for each population and size at maturity both in the presence as in the absence of fish kairomones. Most of the genetic differences could be attributed to a clone isolated from one clearwater pond that is not directly connected to the remainder of the pond complex.

Temperature effects on chemical signalling in a predator–prey system

SUMMARY 1. We investigated the effect of temperature on chemical signalling in a predator–prey model system (planktivorous fish and Daphnia galeata). Life‐history changes in Daphnia in response to chemical cues (kairomones) derived from fish have become a paradigm for chemically induced anti‐predator defences.2. As temperature can affect both predator and prey, we carried out two experiments to disentangle these effects. In order to test for temperature effects on the predator, we kept prey at a single temperature and exposed them to kairomones from fish exposed to two different temperatures. Daphnia exhibited a higher intrinsic rate of population increase (r) when exposed to fish kairomones produced at high rather than low temperature. Assuming a positive correlation between r (because of an earlier maturation and/or increased clutch sizes) and kairomone concentration, our results suggest that kairomone production increases with rising temperature.3. In the second experiment, to study the influence of temperature on the prey, Daphnia were kept at two different temperatures and exposed to fish kairomones produced at one constant temperature. We found no interaction between the effects of fish kairomone and temperature on Daphnia life history, suggesting that temperature does not directly alter life‐history responses to fish kairomones.4. Our results suggest that temperature influences Daphnia life history through its effects on fish kairomone concentration, but that temperature does not affect the strength of the response of Daphnia to the presence of fish.

Host queen killing by a slave-maker ant queen: when is a host queen worth attacking?

A new colony of the slave-making ant Polyergus breviceps is initiated when a newly mated gyne invades a host nest and kills the resident queen. This process seems to result in chemical camouflage of the invading gyne and allows her to usurp the position of colony reproductive. Young, recently mated Formica gynes, however, are not attacked. To determine whether worker and/or immature presence is the basis for aggression, we placed eggs, larvae, pupae and workers from mature F.gnava queens with newly mated F.gnava queens and observed the responses of introducedP.breviceps queens. Because no newly mated gyne was attacked, we tested newly mated F.gnava queens (1) once they had produced eggs, (2) when the offspring reached the larval, pupal and callow stages of development, and (3) every 2 weeks until aggression ensued. Eventually all F.gnava queens were attacked but only 29 weeks after having mated. Thus, although offspring are the ultimate benefit from attacking an established F.gnava queen,P.breviceps queens detect mature queens using another time-dependent feature that is reliably indicative of reproductive status. The similarity of host queen hydrocarbon profiles, often correlated with reproductive status in other ant species, suggests that other compounds reflect queen fecundity and produce a kairomonal effect, or that another cue signals host queen and colony suitability. Our findings indicate P.breviceps gynes have evolved to respond aggressively to a host gyne cue that appears long after mating, preventing attacks on gynes without the workers necessary for colony founding.Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

Antipredator reaction norms for life history traits in Daphnia pulex: dependence on temperature and food

Synergistic effects between temperature and food level on the vulnerability of Daphnia life histories to predation have previously received little attention, despite their potential significance for summer population dynamics. In this investigation, most traits in the early life history of Daphnia pulex altered in response to increasing concentrations of fish kairomone. Although there was some variation attributable to experimental temperature and food treatments, traits exhibited reaction norms which suggested at least some degree of kairomone dose‐dependence. Temperature, food level and their interaction affected the mean values of every trait examined and in some cases also influenced the antipredator response via a three‐way interaction with fish kairomone. The insertion of an extra juvenile instar resulted in later maturation at a larger size for most females raised under conditions of low temperature and low food, but this response was largely suppressed in the presence of fish kairomone. Earlier maturation due to deletion of an instar was observed most frequently under high food and temperature conditions with fish kairomone present, suggesting an effect of kairomone on the size threshold for reproductive development. Principal components analysis was used to produce an index reflecting the net potential vulnerability to fish predation of the suite of life history traits. Vulnerability generally declined with increasing kairomone level as a result of the apparently adaptive alterations in most life history traits. Raised temperature and food level also generally reduced potential vulnerability, but a highly significant interaction between these factors was also found. Potentially important implications of these results for optimal vertical migration and summer population dynamics are discussed.

Response to fish kairomone in Daphnia galeata life history traits relies on shift to earlier instar at maturation

The aim of the present study was to clarify the mechanisms underlying the expression of phenotypic plasticity in Daphnia life history traits in response to fish kairomone and to explore how these mechanisms interact with genetic variation for life history traits. I studied the effect of fish kairomone on life history traits in 16 Daphnia galeata clones. Maturation occurred more often at the earlier instars in response to the fish treatment, resulting in earlier age and smaller size at maturity. The changes in age and size at maturity which occurred in the response to the fish treatment could be attributed to a large extent to this shift. In addition, fish kairomone resulted in smaller instar increments after the maturation process was initiated, but not during the juvenile period. Within groups of animals maturing at the same instar, larger size at birth resulted in larger size at maturity, but had no effect on age at maturity. However, larger size at birth brought about earlier maturity because animals which were larger at birth matured more often at the earlier instar. Fish treatment resulted in more, but smaller, offspring in the first clutch relative to the size of the mother. Genetic variation was found in all measured life history traits. Genetic variation in plasticities of life history traits was not detectable by standard methods, and was only shown when the above mechanisms of expression of life history traits were taken into account. This study illustrates the importance of a thorough understanding of the mechanisms underlying the expression of life history traits, in this case, sources and consequences of maturation in the multiple instars. Not only is this necessary to predict the long-term effect of the environment, but also to understand the response of life history traits and their plasticities to natural selection. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00442-002-0901-0.

The presence of chemicals exuded by fish affects the life‐history response of Ceriodaphnia cf. dubia to chemicals with different mechanisms of action

AbstractThe toxicity of chemicals with different mechanisms of action (3,4‐dichloroaniline, fenoxycarb, and chlorpyrifos) to the cladoceran Ceriodaphnia cf. dubia was examined in the presence and absence of chemicals exuded by fish, termed fish kairomones. A range of life‐history traits were examined, including mean brood sizes, survival, net reproductive rate (Ro) and population growth rate (r). Cladocerans exposed to 3,4‐dichloroaniline showed similar sensitivities in the presence and absence of fish kairomones with respect to all of the life‐history traits examined. The presence of fish kairomones reduced the sensitivity of cladocerans to fenoxycarb with respect to mean brood sizes and r but increased their sensitivity in terms of Ro. The presence of fish kairomones increased the sensitivity of cladocerans to chlorpyrifos with respect to survival, r, Ro, and mean brood sizes. The general trends observed were similar to those shown when C. cf. dubia was exposed to these chemicals under low food conditions, and it is suggested that the effects of fish kairomones on toxicity may be attributed to the reduction in feeding rates observed when C. cf. dubia is exposed to fish kairomones.

The influence of fish kairomones on the induction and vertical distribution of sexual individuals of the Daphnia galeata species complex

To assess the potential production of hybrids and backcrosses in a semi-natural environment, we studied the combined effect of fish kairomone, and food level on the production of males and ephippial females in different clones of five Daphnia taxa from the D. galeata species complex. We also studied the diel vertical migration (DVM) of these sexual daphnids under the same varying conditions. This was done to test the hypothesis that males and ephippial females have different migrating strategies, which would increase their mating probability. The study was carried out in two large-scale indoor mesocosms, the so-called ‘plankton towers’ in the Max-Planck Institute in Plön, Germany. Although all of the Daphnia taxa produced ephippial females in the course of the experiment, only D. galeata produced a significant number of males. Fish kairomones had a significant negative influence on the production of ephippial females. We found no DVM in the D. galeata males. They stayed at a depth between 5 and 6 m both day and night, 1 or 2 m above the thermocline. The ephippial females of D. cucullata x hyalina migrated, whereas ephippial females of the other taxa showed no DVM but came significantly closer to the surface in the presence of fish kairomones. We conclude that males and sexual females co-occur in this species complex both in time and space. Therefore, a regular production of hybrids and backcrosses in this species complex seems likely. Fish kairomones do not seem to significantly influence this process.

Interactions Between Predator Kairomone and Food Level Complicate the Ecological Interpretation of Daphnia Laboratory Results

The effect of food concentration on the phenotypic response of life history traits to two predator kairomones was investigated in Daphnia. For the experiment, one clone of Daphnia galeata was used as the prey organism and solutions containing infochemicals (kairomones) of Chaoborus (phantommidge) and Perca (perch) simulated the presence of potential predators. The combined effect of food level and predator kairomone on phenotypic plasticity of Daphnia life history is complex. At low food levels, the responses in life history traits to kairomones are enhanced. For example, in the Perca treatment, this leads to a younger age at first reproduction. The presence of Chaoborus kairomone decreases survival so that death often occurs before reproduction is reached. This results in a strong decrease in the intrinsic rate of population increase and might contribut to the pronounced summer decline of some Daphnia populations during periods of food shortage.

The presence of chemicals exuded by fish affects the life-history response of Ceriodaphnia cf. dubia to chemicals with different mechanisms of action.

The toxicity of chemicals with different mechanisms of action (3,4-dichloroaniline, fenoxycarb, and chlorpyrifos) to the cladoceran Ceriodaphnia cf. dubia was examined in the presence and absence of chemicals exuded by fish, termed fish kairomones. A range of life-history traits were examined, including mean brood sizes, survival, net reproductive rate (Ro) and population growth rate (r). Cladocerans exposed to 3,4-dichloroaniline showed similar sensitivities in the presence and absence of fish kairomones with respect to all of the life-history traits examined. The presence of fish kairomones reduced the sensitivity of cladocerans to fenoxycarb with respect to mean brood sizes and r but increased their sensitivity in terms of Ro. The presence of fish kairomones increased the sensitivity of cladocerans to chlorpyrifos with respect to survival, r, Ro, and mean brood sizes. The general trends observed were similar to those shown when C. cf. dubia was exposed to these chemicals under low food conditions, and it is suggested that the effects of fish kairomones on toxicity may be attributed to the reduction in feeding rates observed when C. cf. dubia is exposed to fish kairomones.

Interactive effects of fish kairomone and light on Daphnia escape behavior

We investigated the effects of fish kairomone and light intensity on the inducibility and effectiveness of escape behavior in four clones of the water flea Daphnia from different habitats. To characterize and determine the effectiveness of their escape responses, individuals were observed: (i) escaping from the hydrodynamic disturbances of a simulated predator (a small sphere dropped from above); (ii) being preyed upon by small fish (Poecelia reticulata); (iii) responding to encounters with conspecifics in crowded conditions. The simulated predation experiments revealed that when exposed to fish kairomone for 48 h, two Daphnia pulicaria clones, but not two hybrid clones, became about twice as sensitive to fluid disturbances when tested in the light, relative to no-kairomone and dark treatments. When tested in the dark, kairomone had no effect on sensitivity in any clone. All four clones had an all-or-none escape response, in which the strength of the response, as measured by escape distance and speed, was constant regardless of treatment. In the guppy predation trials, kairomone-treated D.pulicaria escaped significantly more often from guppies, in both bright- and dim- light conditions. In dim light, similar to natural lighting conditions, regardless of kairomone, all but the most weakly escaping clone were able to elude attacking guppies in a significant proportion of attacks. Finally, kairomone had no effect on the number of escapes performed by crowded individuals in response to the comparatively weak, non-threatening signals created by other Daphnia, indicating that the kairomone-induced alertness in the D.pulicaria clones did not make them 'excessively' sensitive. The results suggest that Daphnia escape behavior is under complex and efficient environ- mental regulation, and may play a significant role in aquatic trophic relationships.

Environmental stress and local adaptation in Daphnia magna

The effects of fish kairomones, crowding chemicals, and day length on the life–history traits of a set of 16 Daphnia magna clones, derived from four populations that differ in fish‐predation pressure, were studied. Significant among‐population differences were observed, the differences being in concordance with the hypothesis of local adaptation. The among‐population genetic differences were not mediated through a change in response to fish kairomones, but through an overall smaller body size, smaller eggs, and a higher number of eggs in clones derived from habitats in which fish are present. Using a model, we show that the observed changes in life‐history characteristics may lead to differences in fitness under different predation regimes, such that populations from habitats with fish have highest fitness under fish‐predation regimes and populations without a fish background have higher fitness values under invertebrate predation regimes.

The effects of a pesticide on inducible phenotypic plasticity in Daphnia

Many species of zooplankton can detect chemical signals (kairomones) released by their predators and respond with defensive morphological and life-history changes. Daphnia longicephala were exposed to five different concentrations of the carbamate insecticide, carbaryl, in the presence and absence of kairomones released by Anisops gratus (Hemiptera: Notonectidae). In the absence of Anisops kairomone, there was a negative correlation between carbaryl concentration and length and brood size at maturity. Growth and reproduction were significantly impaired at carbaryl concentrations ⩾0.32 μg/litre. There was no effect of carbaryl on age at maturity and it did not induce crest growth in the absence of kairomone. In the presence of kairomone, D. longicephala developed a large crest, but took longer to reach maturity than control animals. A concentration of 3.2 μg/litre carbaryl decreased relative crest size of 3-day-old daphnids but did not affect crest size of adults. The Anisops kairomone dramatically altered the effects of carbaryl on the life-history responses of D. longicephala at maturity. There was a positive correlation between the concentration of carbaryl and age, length, and brood size at maturity. The effects of kairomone on life-history parameters are explained using a size threshold for maturation hypothesis.

Biological and chemical characterization of a kairomone excreted by the bean aphids, Aphis fabae Scop. (Hom., Aphididae) and its effect on the predator Metasyrphus corollae Fabr. I. Isolation, identification and bioassay of aphid‐kairomone

Abstract: The results obtained are summarized as follows: (1) the active compounds of aphid's odour stimulated the syrphid females to deposit significantly higher percentages of eggs. These chemical compounds could be isolated by the solvent n‐pentane. (2) Gas chromatography mass spectral analysis of n‐pentane fractions of aphid's odour revealed the presence of several active peaks of hydrocarbon compounds. The active peaks ranged from docosane (C22) to octacosane (C28). Also, GC‐mass spectral analysis of n‐pentane fractions of the aphid‐extract supernatant showed the same chain of hydrocarbon compounds which is present in the aphid odour. (3) Bioassay of the different cosane compounds showed that the different concentrations of tricosane, tetracosane, pentacosane and hexacosane have a kairomonal effect on the syrphid females and the second concentration of C23CII, C24CII, C25CII and C26CII stimulated the syrphid females to deposit a significantly higher percentage of eggs. While hexacosane (C26) was the most abundant hydrocarbon compound in aphid kairomone, tricosane (C23) was the most active hydrocarbon compound. (4) Bioassay of the different mixtures of cosane compounds showed that HCM1, HCM2, HCM3, HCM4, HCM5 and HCM6 have a kairomonal effect on the syrphid females. The highest percentage of eggs was laid under the effect of the fourth mixture (HCM4) which contains tricosane (C23), tetracosane (C24), pentacosane (C25), hexacosane (C26) and octacosane (C28). (5) The chain of non‐volatile hydrocarbon compounds of aphid‐kairomone is secreted along with the cornicle secretion which contains volatile compounds. This kairomone stimulate the oviposition of syrphid females when it is received mechanically by the antennae. (6) The present study showed the importance of the different mixtures of cosane compounds as aphid‐kairomone. The use of aphid‐kairomone could be promising in aphid biological control instead of the heavy use of insecticides.

Increasing rates of parasitism of the larval parasitoid Bracon brevicornis (Hym., Braconidae) by using kairomones, pheromones and a supplementary food

Abstract: The kairomonal effect of hexane extract of the larvae of Ostrinia nubilalis and Sesamia cretica on Bracon brevicornis adults was evaluated through olfactometer tests. The parasitoid males showed no definite response to any kairomone. Females were attracted to the kairomone of S. cretica more than to that of O. nubilalis. Highly significant effect of the sex pheromone of O. nubilalis on the females of B. brevicornis was recorded. Kairomones (hexane extracts of larvae) varied in their effect on the released B. brevicornis parasitoids. The kairomone of S. cretica increased the parasitisation from 7.74 to 17.05%, while the kairomones of O. nubilalis and of Spodoptera littoralis were not significantly effective. Spraying molasses solution (10%) on the corn stalks before releasing B. brevicornis parasitoids increased the rate of parasitism from 7.74 to 28.21%. The concentration of 5% gave insignificant increase in the parasitisation rate.