Prey-predator relationship between Lipaphis erysimi Kalt. (Hom., Aphididae) and Coccinella septempunctata L. (Col., Coccinellidae). II. Effect of host plants on the functional response of the predator

The present paper examines the effect of the host plants Brassica oleracea, Raphanus sativus and Brassica campestris on which Lipaphis erysimi was reared, on the functional response of the grub of Coccinella septempunctata . The functional response of the grub of C. septempunctata is of type II. The amount of prey consumption increases significantly with the increase of prey density and is maximum in B. oleracea- reared aphids, followed by those reared on R. sativus and B. campestris . The percentage prey consumption declined throughout. This decrease was a maximum for aphids reared on B. campestris followed by R. sativus - and B. oleracea -reared aphids. Analysis of variance also confirmed that the number and percentage prey consumption was significantly influenced between the three host plants and between 12 prey densities. Results show that C. septempunctata has a greater liking for aphids reared on B. oleracea rather than those reared on the other plants that were tested.     

Predatory effect of Coccinella septempunctata on Thrips tabaci and Trialeurodes vaporariorum

Abstract:  The predatory effect of adult ladybird Coccinella septempunctata L. on adults of thrips, Thrips tabaci Lindeman, and whiteflies, Trialeurodes vaporariorum (Westwood), was examined in controlled environment chambers, on tomato leaves, in transparent small plastic cages at proportions of 1/(10 + 10), 1/(20 + 20), 1/(30 + 30) and 1/(40 + 40) predator/number of thrips and whiteflies. We conclude that C. septempunctata could be used with success for the biological control of thrips and whiteflies in greenhouse crops, with almost the same effectiveness as for aphids, at predator/prey proportions near 1 : 30. Additionally, it was found a prey preference for T. tabaci in comparison with T. vaporariorum . According to the model used, effective predation is correlated with predator/prey ratio rather than to prey preference.     

Assessment of temperature effects on the development and fecundity of Pullus mediterraneus (Col., Coccinellidae) and consumption of Saissetia oleae eggs (Hom., Coccoida)

Eggs, larval and nymphal periods and fecundity of Pullus mediterraneus were examined under 16 h light : 8 h dark combined with six constant temperatures: 15, 20, 25, 30, 35 and 40°C. Eggs of Saissetia oleae were used as prey. The developmental time at 15, 20, 25, 30 and 35°C was 17.23, 4.5, 2.64, 1.67, 1.28 days for eggs and 98.47, 68.88, 53.94, 28.96, 36.51 days for larval–pupal duration, respectively. At 7°C no eggs hatched, and at 40°C all the stages died after 36 h of maximum exposure except the three last stages. The fecundity of females rearing at different temperatures ranged between 1.7 eggs at 15°C and 601.86 eggs at 30°C. The pre-oviposition period ranged between 23.75 days at 15°C and 3.47 days at 35°C. The consumption of S. oleae eggs by the larvae reached 597.69 eggs during the pre-imaginal development. Females attacked more eggs than males averaging 77.69 ± 22.34 eggs per 4 day period compared with 46.97 ± 10.12 eggs per 4 day period for males.     

Rearing and life table of reduviid predator Rhynocoris marginatus Fab. (Het., Reduviidae) on Spodoptera litura Fab. (Lep., Noctuidae) larvae

The tobacco armyworm, Spodoptera litura Fab., a serious pest of many cultivated crops was evaluated as prey for the reduviid predator, Rhynocoris marginatus Fab. The development, sex ratio, fecundity, hatchability and adult longevity of R. marginatus were investigated in the laboratory. Moreover, a life table was constructed for this predator. Observations clearly indicated that total developmental period of this predator was 46.71±1.58 days. In sex ratio, no significant difference was observed between male and female predators. The pre-oviposition period lasted for 18.64±0.76 days and it was 6.31 times shorter than the oviposition period. Female predators lived longer (128.04±8.48 days) than males (82.84±11.09 days). The total number of eggs laid per female predator in its life span was 405.28±22.15 eggs and the incubation period lasted for 6.81±0.10 days. Life-table studies showed that the intrinsic rate of increase was 0.063 female/day. The population multiplied 292.28 times in the cohort generation time of 103.933 days.     

Effect of starvation time on the prey capture behaviour, functional response and population growth of Asplanchna sieboldi (Rotifera)

1. We examined the effect of different periods of prior starvation(from 30 min to 16 h) on the prey capture behaviour, and functional and numerical responses of the predatory rotifer Asplanchna sieboldi using the rotifer Brachionus calyciflorus as prey.
2. Feeding activity (i.e. encounter, attack, capture and ingestion) by Asplanchna increased significantly with increasing prey densities from 2 to 16 mL⁻⁻¹ and with increasing prior starvation periods from 0.5 to 8 h.
3.  Asplanchna sieboldi showed a type II functional response at all the prior starvation periods tested. The asymptotic prey density was highest after 8 h of starvation.
4. The instantaneous population growth rate of A. sieboldi ranged from 0.089 ± 0.044 (when starved for 8 h in every 24 h and at a prey density of 2 individuals mL⁻⁻¹ for the other 16 h) to 1.015 ± 0.142 in the control (no starvation and at a prey density of 16 individuals mL⁻⁻¹). The effect of starvation time on the numerical response was evident only at the higher prey density.     

Mass-rearing biology of Fopius vandenboschi (Hym., Braconidae)

Abstract:   Basic biological information concerning the reproductive activities of Fopius ( Biosteres ) vandenboschi (Fullaway) (Hym., Braconidae, Opiinae) were determined to facilitate insectary mass production. Mean (±SE) progeny production per generation (yield) of 200 ♀♀ F. vandenboschi was 6835.8 ± 433.2 and 3755.8 ± 112.4 parasitoids, with 24-h exposure to second instar Bactrocera dorsalis (Hendel), and Ceratitis capitata (Wiedemann), respectively. Ceratitis capitata as a factitious host was more sensitive to parasitism, producing a significantly higher percentage of uneclosed host puparia frequently containing parasitoid cadavers (22.5 ± 0.8%), than B. dorsalis (3.4 ± 0.2%). The overall mean production of female offspring was ≥50%♀♀ in both host species. Unlike several other opiine parasitoids, young (5-day-old) females of F. vandenboschi produced low proportion of daughters (26–37%♀♀) and significantly shifted production to female-biased offspring (53–71%♀♀) at older age intervals (16–30 days). Based on the parasitoid yield data with a 24-h exposure period to second instar host larvae of B. dorsalis , about 150 cage replicates (of 200 ♀♀ each) may be sufficient to mass produce about 1 million parasitoids of F. vandenboschi during the reproductive period of 5–30 days, with an average of 56% female offspring. A short oviposition exposure period of 6 h was not optimal for mass production of F. vandenboschi . Total yield at 6 h exposure was one-fifth the production at 24-h exposure, using B. dorsalis hosts.     

Diel rhythmicity of prey-search activity and its predominance over starvation in the lady beetle, Coccinella septempunctata bruckii

ABSTRACT. The locomotor activity of the lady beetle, Coccinella septempunctata bruckii Mulsant (Coleoptera: Coccinellidae), was recorded during food deprivation in LD 16:8 h and continuous light. Activity was relatively low immediately after the lady beetle was fed to satiation but increased from 4 to 24 h later. It thereafter gradually decreased to a low level when the food was withheld for several days. Over a period of 10 days of starvation the beetles showed a high level of activity throughout the photophase and a low level during the scotophase in LD 16:8 h. In continuous light this rhythmic pattern persisted, with a free-running period of c. 22 h, significantly shorter than 24 h. The results suggest that the endogenous circadian timing predominates over 'hunger' as a determinant of search activity. The lady beetle accepted and consumed aphid prey presented at night, but the number of prey consumed was significantly lower than in the light. This suggests that, during the dark, activity related to prey-searching is suppressed, though lady beetles are able to accept and consume prey even at night.     

Dispersal of Podisus nigrispinus (Het., Pentatomidae) nymphs preying on tomato leafminer: effect of predator release time, density and satiation level

Abstract:   The dispersal potential of nymphal stinkbug, Podisus nigrispinus (Dallas, 1851) (Het., Pentatomidae) preying on larvae of the tomato leafminer Tuta absoluta (Meyrick, 1917) (Lep., Gelechiidae) was studied in an open-sided greenhouse. The parameters investigated were (1) the density of nymphs released per plant (one or five); (2) the release time (0600 and 1800 h); and (3) predator satiation level (satiated and 24-h-starved nymphs). Tomato plants were infested with larvae of the tomato leafminer (one third or fourth instar per leaf). The evaluations started 30 min after the release of predators second instar and hourly evaluations were carried out over 36 and 24 h for release times of 0600 and 1800 h, respectively. Starved nymphs released in the morning, either alone or in groups of five, dispersed faster than satiated nymphs. All of the starved individuals had left the plant by the end of the observation period, whereas 25 and 36% of the satiated nymphs released alone and in groups, respectively, stayed on the plant until the end of the observation period. Both satiated and starved nymphs showed slower rates of dispersal when released at 1800 h. Satiated nymphs delayed prey attack up to 9 h, whereas starved individuals started to attack T. absoluta caterpillars 1 h after their release at both densities. Our findings suggest more effective biological control of T. absoluta is possible with the release of second instar nymphs of P. nigrispinus when starved for 24 h prior to release and then released either in the morning or in the evening.     

Effect of microsporidian infection in Lacanobia oleracea (Lep., Noctuidae) on prey selection and consumption by the spined soldier bug Podisus maculiventris (Het., Pentatomidae)

Abstract:  The predatory behaviour of Podisus maculiventris was investigated when this bug was presented with Lacanobia oleracea larvae infected with the microsporidian pathogen Vairimorpha necatrix . In choice tests, adult predatory bugs attacked V. necatrix -infected L. oleracea prey in similar numbers to uninfected larvae. Exposure to infected prey during nymphal development increased the rate at which adult bugs attacked diseased L. oleracea larvae. Fifth instar P. maculiventris nymphs, however, attacked infected prey in the majority of cases (>80% of occasions). Consumption of healthy and infected prey was measured for both adult and nymphal bugs. Over the course of 1 week, the mean number of V. necatrix -infected prey eaten by P. maculiventris adults (7.0 ± 0.82) was approximately twice the number of uninfected prey consumed (3.8 ± 0.42). Similarly, the number of prey larvae attacked by the bug over the course of the final nymphal stadium was also increased, with 2.9 ± 0.42 uninfected larvae eaten as opposed to 4.9 ± 0.27 V. necatrix -infected prey. However, small-scale investigations into the rate of P. maculiventris reduced small populations of L. oleracea indicated that the combination of the predator and pathogen would produce, at best, an additive effect.     

Feeding history effects on feeding responses of Rhagoletis indifferens (Dipt., Tephritidae) to GF-120 and Nulure

Abstract:  Effects of feeding history on feeding responses of western cherry fruit fly, Rhagoletis indifferens Curran, to the commercial protein baits GF-120 and Nulure were determined in the laboratory. Flies were kept on 5% sucrose alone or yeast extract and sucrose (Y + S) for 3–7 or 14–16 days and exposed to 24-h-old GF-120 or Nulure drops on artificial leaves. Numbers and durations of feeding events on leaves and durations of non-feeding events were recorded over 1-h periods. Experiments were also conducted to determine effects of Y + S feeding sequences on responses to Nulure, of starvation after sucrose or Y + S feeding on responses to Nulure, and of feeding history on mortality after exposure to GF-120 and Nulure. Protein-deprived flies consistently fed more times on GF-120 and Nulure than protein-fed flies and fed longer. One day of exposure to Y + S or 16 h of starvation after exposure to sucrose caused greater feeding on Nulure than 7 days of exposure to Y + S or 16 h of starvation after exposure to Y + S. Durations of non-feeding events on leaves with sucrose or bait were similar in protein-deprived and -fed flies. Responses of 4- to 6-day-old flies kept on sucrose to 0- and 24-h-old GF-120 or Nulure were similar. More flies kept on sucrose were paralysed or dead at 6–32 h after exposure to GF-120 or Nulure with spinosad than flies kept on Y + S. Results show that complete or long periods of protein deprivation and starvation after sucrose feeding increased feeding responses to GF-120 and Nulure. The general lack of differences in durations of non-feeding events on leaves with sucrose or GF-120 or Nulure in protein-deprived and -fed flies suggests that most protein-deprived flies found baits through chance encounters following normal movement.     

Chloroplast DNA content in Dinophysis (Dinophyceae) from different cell cycle stages is consistent with kleptoplasty

Kleptoplasty is the retention of plastids obtained from ingested algal prey, which can remain temporarily functional and be used for photosynthesis by the predator. With a new approach based on cell cycle analysis, we have addressed the question of whether the toxic, bloom-forming dinoflagellate Dinophysis norvegica practice kleptoplasty or if they replicate their own plastid DNA. Dividing (G2) and non-dividing (G1) D. norvegica cells from a natural population were physically separated with a flow cytometer based on their DNA content. Average numbers of nuclear and plastid rDNA copies were quantified with real-time PCR both in the G1 and G2 group. Cells from the G1 group contained 5800 ± 340 copies of nuclear rDNA and 1300 ± 200 copies of plastid rDNA; cells from the G2 group contained 9700 ± 58 copies of nuclear rDNA and 1400 ± 220 copies of plastid rDNA (mean ± SD, n  = 3). The ratio G2/G1 in average rDNA copies per cell was 1.67 for nuclear DNA and 1.07 for plastid DNA. These ratios show that plastid acquisition in D. norvegica is either uncoupled with the cell cycle, or plastids accumulate rapidly in the beginning of the cell cycle owing to feeding, as would be expected in a protist with kleptoplastic behaviour but not in a protist with own plastid replication. In addition, flow cytometry measurements on cells from the same population used for real-time PCR showed that when kept without plastidic prey, live Dinophysis cells lost on average 36% of their plastid phycoerythrin fluorescence in 24 h. Together these findings strongly suggest that D. norvegica does not possess the ability for plastid replication.     

Effects of starvation on the search path characteristics of Orius majusculus (Reuter) (Het., Anthocoridae)

Abstract: Orius majusculus (Reuter) is a polyphagous predator bug used to control western flower thrips Frankliniella occidentalis (Pergande). As physiological factors may be highly influential upon the predatory behaviour of Orius spp. we studied the possible impact of starvation on the search path of this bug. Orius majusculus was maintained on a diet of Ephestia kuehniella Zeller (Lep., Pyralidae) eggs in laboratory. Adults were collected immediately after the imaginal moult and were individually placed in Petri dishes with abundant food. Each adult was randomly assigned to one of the following five treatments: immediate observation or starved for 2, 6, 9 or 12 h prior to observation. The observation procedure consisted of placing a single O. majusculus adult at the centre of an empty arena. The displacement of each insect was recorded with a video camera until it had reached the limits of the arena. The recorded paths were digitized and the digitized search path was used to calculate the mean walking speed, the number of stops per second, the duration of stops and the diffusion rate. The results clearly show that, in comparison with unstarved bugs, insects that experienced 6 h of prey deprivation walked more slowly, stopped more frequently and for longer periods, and had a lower rate of diffusion away from the release point. In contrast, all search path variables returned to the levels measured in unstarved bugs in the group that experienced the longest period of starvation (12 h), whereas groups of O. majusculus that had experienced 2 or 9 h of prey deprivation presented intermediate values for all the variables tested. Starvation produced evident changes in the search path characteristics that we assume to be related to physiological states of hunger and energy availability. These behavioural changes related to physiological state could have consequences for the use of this pirate bug in biological control.     

Functional response of Picromerus bidens: effects of host plant

Abstract:  The influence of three solanaceous plants (tomato, sweet pepper and eggplant) on the functional response of the predatory bug Picromerus bidens to densities of fourth-instar larvae of the beet armyworm Spodoptera exigua was assessed. Logistic regression indicated a type II functional response on all host plants. Over all prey densities, P. bidens killed significantly fewer fourth instars of S. exigua on tomato than on sweet pepper or eggplant (1.96 ± 0.17 vs. 4.37 ± 0.19 and 3.90 ± 0.15 larvae per predator per 24 h respectively). A higher theoretical maximum predation rate was estimated on sweet pepper (11.1 prey larvae per day) and eggplant (7.4) than on tomato (5.4). The mean number of prey killed per day by P. bidens females ranged from 0.78 at a density of one prey on tomato to 8.45 at a density of 24 prey on sweet pepper. The data indicated that the estimates of handling time ( T _h) and attack rate ( a ) were highly affected by host plant. Based on asymptotic 95% confidence intervals, a lower attack coefficient was found on tomato (0.02 h⁻¹) than on sweet pepper or eggplant (0.07 and 0.11 h⁻¹ respectively). On the other hand, handling times were significantly longer on tomato (4.42 h) and eggplant (3.23 h) than on sweet pepper (2.15 h). This laboratory study suggests that plant characteristics influence the ability of P. bidens to respond to changes in prey density.     

The Effects of Experimentally Elevated Testosterone and Food Deprivation on Food Consumption and Prey Size Preferences in Male Dark-Eyed Juncos (Junco hyemalis, Emberizidae: Passeriformes)

Numerous studies have shown that the experimental elevation of circulating levels of testosterone reduces parental behaviour in male birds, particularly the provisioning of young. The mechanisms responsible for this change in behaviour are not fully understood. In this study, we examine the effects of elevated testosterone on food consumption and prey selection, both of which have potential consequences for nestling provisioning behaviour. We manipulated testosterone and performed two experiments on a captive, non-breeding population of male dark-eyed juncos ( Junco hyemalis ) on long day-lengths. In the first experiment, we subjected juncos to 3 h of food deprivation and compared food consumption and prey size selection by males with elevated testosterone (testosterone males) to that of control males. Testosterone males consumed more food than control males and showed a preference for larger prey. In a second experiment in which small prey were more abundant than large prey, food consumption and prey size preferences did not differ between testosterone and control males. We also manipulated the duration of food deprivation in the second experiment. Males of both treatments consumed more small prey under conditions of mild (1 h) or moderate (5 h) food deprivation and consumed more large prey under conditions of intermediate (3 h) food deprivation. We discuss our results and the effects that testosterone has on self-maintenance behaviour and male parental effort.     

Diel feeding habits of juveniles of Mullus surmuletus (Linneo 1758) in the lagoon of the Stagnone di Marsala (Western Sicily, Italy)

Diet composition, feeding rhythm, gastric evacuation rate and daily ration were investigated in juvenile Mullus surmuletus (Linneo 1758). Fish were collected in the lagoon of the Stagnone di Marsala in western Sicily, in July 1995, during a 24 h sampling period. Copepoda, Polychaeta, Amphipoda and Tanaidacea were shown to be the most frequent prey items. The feeding index values showed two different daily feeding times. A unimodal trend in the daily rhythm of food consumption was derived, with a peak in feeding between 1200 and 2000 h. Gastric evacuation in juvenile M. surmuletus is best described by an exponential model, with a gastric evacuation rate R  = 0.66 g h⁻¹ ( r = 0.88) ( T  = 24.45 ± 0.64°C). The amount of food consumed daily, calculated according to the Elliott and Persson model, was 0.079 g, equal to about 8% of the average dry weight of the fish.     

Interaction between plant resistance and predation of Aphis fabae (Homoptera: Aphididae) by Coccinella septempunctata (Coleoptera: Coccinellidae)

We investigated the compatibility of host plant resistance to the black bean aphid in the faba bean crop with the use of the predatory ladybird beetle for biological control under laboratory and greenhouse conditions. Greenhouse experiments indicated that apteriform Aphis fabae reproduced on Vicia faba major (susceptible) and on 79S4 (partially resistant) cultivars at different rates. During the entire experimental period, aphids built up higher populations on V. faba major than on 79S4 cultivar. Aphid numbers on 79S4 were about 37% of those on V. faba major after 14 days. Release of a newly hatched Coccinella septempunctata larva onto each plant significantly reduced aphid density to 32.8% and 57.2% on V. faba major and 79S4 on day 14, respectively. Partial resistance combined with predation was more effective in lessening aphid numbers on faba bean than either the predator or the plant resistance alone. Laboratory tests showed that prey, A.   fabae , raised on susceptible cultivar was more suitable for the predator as food source, enhancing the development rate and fecundity than aphids fed on the partially resistant cultivar. Consumption of aphids reared on susceptible cultivar significantly increased the female fecundity and fertility of C. septempunctata by 37.7% and 33.2%, respectively, more than those fed with aphids from partially resistant cultivar. Pre-oviposition time was shortened by 4.5 days, and oviposition period was extended by 11.4 days. Feeding the predator on aphids from the partially resistant cultivar prolonged the embryonic larval developmental time and the time required from egg laying to adult emergence by 19.8, 10.1 and 32.5 h, respectively. Adult longevity was not influenced by the aphid source. The results are discussed in relation to the compatible utilisation of host plant resistance and biological control in the integrated management of aphids.     

Voracity and feeding preferences of two aphidophagous coccinellids on Aphis citricola and Tetranychus urticae

Voracity and feeding preferences of adult Coccinella septempunctata L. and Harmonia axyridis Pallas (Coleoptera: Coccinellidae, tribe Coccinellini) were evaluated in the laboratory on a common prey, the spirea aphid, Aphis citricola van der Goot (Homoptera: Aphididae), and on the twospotted spider mite, Tetranychus urticae Koch (Acarina: Tetranychidae), a prey previously unrecorded for these two predators. The experiments were carried out in the laboratory on apple saplings (Malus domestica Borkhausen). Adult males and females of H. axyridis consumed significantly more mites than adults of C. septempunctata. For H. axyridis, males consumed 41.3 spider mites in 24 h and females 48.4, whereas for C. septempunctata males consumed 14.1 prey and females 15.2. The consumption of spirea aphids by the males was similar for the two species. Consumption by the females was significantly greater for H. axyridis (46.5) than for C. septempunctata (22.2). The two coccinellids showed a significant preference for A. citricola in the presence of T. urticae. This preference was more pronounced for C. septempunctata. The total number of prey consumed and the percentage of exploited biomass decreased significantly for C. septempunctata and stayed relatively constant for H. axyridis as the number of mites increased in the prey ratio. Our results suggest that T. urticae is only an alternative prey for both predators, and that H. axyridis should be more efficient than C. septempunctata in a prey assemblage with aphids and mites.     

Biology and efficacy of the predatory mite, Amblyseius longispinosus (Evans) (Acari, Phytoseiidae) as a biological control agent of Eotetranychus cendanai Rimando (Acari, Tetranychidae)

Egg, larval, protonymphal and deutonymphal stages of Amblyseius longispinosus (Evans) that fed on Eotetranychus cendanai , required 2.02 ± 0.13, 0.57 ± 0.17, 1.07 ± 0.31 and 1.16 ± 0.53 days, respectively. The total developmental time was 4.79 ± 0.61 days. Female longevity averaged 14.61 ± 2.88 days in which 19.54 ± 6.36 eggs/female or 1.33 ± 0.29 eggs/female per day were laid. The highest predation rate was detected at a prey density of 40–50. Amblyseius longispinosus could be employed as the biological control agent of E. cendanai both in laboratory and greenhouse conditions at the predator : prey ratio of 1 : 30 to 1 : 50.     

Summer predation rates on ungulate prey by a large keystone predator: how many ungulates does a large predator kill?

Estimates of predation rates by large predators can provide valuable information on their potential impact on their ungulate prey populations. This is especially the case for pumas Puma concolor and its main prey, mule deer Odocoileus hemionus . However, only limited information on predation rates of pumas exist where mule deer are the only ungulate prey available. I used VHF telemetry data collected over 24-h monitoring sessions and once daily over consecutive days to derive two independent estimates of puma predation rates on mule deer where they were the only large prey available. For the 24-h data, I had 48 time blocks on female pumas with kittens, 43 blocks on females without kittens and 30 blocks on males. For the daily consecutive data, the average number of consecutive days followed was 51.5±4.2 days. There were data on five female pumas with kittens, five pregnant females and nine females without kittens. Predation rates over an average month of 30 days from the 24-h monitoring sessions were 2.0 mule deer per puma month for males (15.1 days per kill), 2.1 mule deer per puma month (14.3 days per kill) for females without kittens and 2.5 mule deer per puma month (12.0 days per kill) for pregnant females and females with kittens. For the consecutive daily data, females without kittens had an estimated predation rate of 2.1±0.14 mule deer per puma month (14.9±0.90 days per kill). Pregnant and females with kittens had predation rates of 2.7±0.18 and 2.6±0.21 mule deer per puma month, respectively (11.4±0.72 and 12.0±1.1 days per kill, respectively). Predation rates estimated in this study compared with those estimated by energetic demand for pumas in the study area but were lower than other field derived estimates. These data help increase our understanding of predation impacts of large predators on their prey.     

Nettle extract effects on the aphid Myzus persicae and its natural enemy, the predator Macrolophus pygmaeus (Hem., Miridae)

Abstract:  The effect of water extract of Urtica urens L. on the biological characteristics and population parameters of Myzus persicae (Sulzer) and its natural enemy, the polyphagous predator Macrolophus pygmaeus (Rambur) was investigated on eggplants. Plant material was extracted in deionized water (1 : 5 w/w) for 24 h. Three applications were made at 5-day intervals using the nettle extract, with deionized water as the control. The effect of the extract on survival, duration of nymphal development, pre-reproductive period, fecundity and longevity of both insects was studied at conditions of 25 ± 1°C, 65 ± 5% relative humidity and photoperiod of 16 : 8 h (light : dark). The results showed that the application of nettle extract significantly reduced the fecundity of M. persicae (20% on average) but did not result in a substantial lowering in its intrinsic rate of population increase. However, the predator's biological characteristics and population parameters were not affected by the application of this plant extract. The importance of these results for the use of nettle extract in the management of M. persicae along with its compatibility with the use or conservation of M. pygmaeus is discussed.