Prey quality dependent growth,development and reproduction of a biocontrol agent,Cheilomenes sexmaculata (Fabricius) (Coleoptera: Coccinellidae)

Growth, development and reproduction of a ladybird beetle, Cheilomenes sexmaculata (Fabricius) were investigated in relation to seven aphid species, viz. Aphis craccivora Koch, Aphis gossypii Glover, Rhopalosiphum maidis (Fitch), Myzus persicae (Sulzer), Uroleucon compositae (Theobald), Lipaphis erysimi (Kaltenbach) and Aphis nerii Boyer de Fonscolombe on specific hosts. Maximum prey consumption, percent larval survival, developmental rate, weight of different life stages, percent adult emergence, adult longevity and fecundity of C. sexmaculata were recorded on A. craccivora, and minimum on A. nerii. A linear relationship was found between development rate and weight of adult, daily prey consumption and relative growth rate, log weights of adult males and females, and female longevity and total fecundity. On the basis of overall performance of ladybird the order of suitability of prey species was A. craccivora>A. gossypii>R. maidis>M. persicae>U. compositae>L. erysimi>A. nerii.     

Influence of six aphid prey species on development and reproduction of a ladybird beetle, Coccinella septempunctata

Pre-imaginal development, immaturesurvival, and reproduction of a ladybird, Coccinella septempunctata Linnaeus, werestudied in response to six aphid species, Aphiscraccivora Koch, Aphis gossypii Glover,Aphis nerii Boyer de Fonscolombe,Lipaphis erysimi (Kaltenbach), Myzuspersicae (Sulzer) and Uroleuconcompositae (Theobald) to quantify theirrelative suitability as prey. Pre-adultdevelopment was shortest (13.93 ± 0.12 days)when fed on L. erysimi and longest(22.85 ± 0.10 days) on A. nerii. Immaturesurvival, adult emergence, growth index,relative growth rate, development rate, maleand female longevity, oviposition period,fecundity and hatching percent were maximal, i.e. 73.47 ± 0.89%, 90.07 ± 1.43%,8.62 ± 0.23, 1.52 ± 0.02, 0.07,81.10 ± 1.26 days, 85.70 ± 1.45 days,69.80 ± 1.32 days, 1764.10 ± 8.46,and 87.88 ± 1.05, respectively when C.septempunctata were fed on L. erysimi.The same parameters were minimal, i.e.43.86 ± 1.33%, 71.65 ± 2.75%,2.02 ± 0.08, 0.49 ± 0.02, 0.04,44.40 ± 1.39 days, 53.50 ± 1.00 days,16.40 ± 0.60 days, 203.20 ± 11.83, and48.68 ± 2.06, respectively on A. nerii. Theweights of different ladybird life stages weremaximal after feeding on L. erysimi and minimalon A. nerii. Regression analyses of thedata revealed linear relationships betweendevelopment rate and weight of adult; dailyprey consumption and relative growth rate; logweight of adult male and female; and longevityand fecundity of female. On the basis of thesefindings, the order of suitability of aphidspecies for C. septempunctata is L. erysimi >M. persicae > A. craccivora > A. gossypii >U. compositae > A. nerii. Thus, the presentinformation can be utilized for the massrearing of C. septempunctata by supplyingthe best food and can also help in theprediction of the relative abundance of theladybird on different aphid infestations in thefields.     

Functional response of two aphidophagous ladybirds searching in tandem

The functional response of two ladybird species, Propylea dissecta (Mulsant) and Coccinella transversalis Fabricius in combination was studied in an effort to determine the impact of two predators on the increasing density of aphid, Aphis gossypii Glover infesting leaves of bottle gourd, Lagenaria vulgaris Seringe. The ladybirds were exposed to prey density in three combinations using adult females: (i) one P. dissecta and one C. transversalis together, (ii) two P. dissecta, and (iii) two C. transversalis, for 24 h. Prey consumption increased curvilinearly with prey density in all three combinations. It was maximum when heterospecifics searched together. The prey were handled and consumed significantly faster (9.51 min) by heterospecifics in combination, followed by two C. transversalis (11.32 min) and two P. dissecta (12.52 min). The attack rate was maximum (0.00274) by heterospecifics followed by the two C. transversalis (0.00166) and two P. dissecta (0.00092). The synergistic effect on the prey consumption may possibly be due to spatial distribution of P. dissecta and C. transversalis in terms of feeding sites, with the former being negatively, and the latter being positively geotactic. Field release of two predator species in tandem is recommended for biocontrol of A. gossypii because of the potential for synergistic action by these natural enemies.     

Prey species affects the performance of the aphidophagous ladybird,Coelophora saucia

Performance of ladybird, Coelophora saucia (Mulsant) was studied on seven aphid species in terms of various life attributes. Immature stages developed fastest and survived most on Aphis craccivora. Longevity, fecundity and egg fertility of adults were highest on A. craccivora. Age specific fecundity was triangular in shape with the occurrence of peak oviposition at an early age on A. craccivora and at a later age on Lipaphis erysimi. The net reproductive rate, intrinsic rate of increase, and finite rate of increase of C. saucia were highest on A. craccivora and lowest on L. erysimi. Owing to better performance of C. saucia on A. craccivora, this is considered as the most suitable prey followed by Myzus persicae, Aphis gossypii, Rhopalosiphum maidis, Ceratovacuna silvestrii, Aphis nerii and L. erysimi. It is the first attempt to evaluate prey suitability of this ladybird based on several attributes.     

Functional and numerical responses of Propylea dissecta (Col., Coccinellidae)

The functional response of a ladybeetle, Propylea dissecta, to increasing density of aphid, Aphis gossypii, was of the curvilinear shape depicting Holling's type II response with fourth instar larva being the most voracious stage when compared with adult male and female. Prey handling time by different predatory stages decreased from 65.45 to 8.72 min with increase in prey density from 25 to 800. The predator aggregation and high prey density reduces the searching efficiency of the predator. Area of discovery was highest (1.4437) when a single predator was searching at minimum aphid density (25) and lowest (0.0366) when eight predators were searching at a constant aphid density (200). Mutual interference and quest constants were 0.75 and 0.40, respectively. The reproductive numerical response, in terms of eggs laid, increased curvilinearly with prey density and female laid 70.5 ± 5.55 eggs when exposed to highest prey density (400) and 12.3 ± 0.79 eggs at lowest prey density (10). The similar shapes of both functional and reproductive responses indicate that both responses are interlinked and function simultaneously.     

Lysiphlebus testaceipes,an introduced aphid parasitoid in portugal [Hym.: Aphidiidae]

Lysiphlebus testaceipes (Cresson), an exotic parasitoid species introduced in 1973–74 into southern France and subsequently widespread over the whole mediterranean France, Italy and Spain has become established even in Portugal since 1985. It was found on the southern coast of Portugal parasitizingAphis nerii Boyer de Fonscolombe. In 1986 it spread towards the North, its host range expanded and now includesAphis chloris Koch,Aphis citricola van der Goot,Aphis fabae Scopoli,Aphis frangulae Kaltenbach,Aphis gossypii Glover,A. nerii, Aphis parietariae Theobald,Aphis sedi Kaltenbach,Toxoptera aurantii (Boyer de Fonscolombe). The proved complete development and a high parasitization ofL. testaceipes onA. citricola is the 1st case in the whole Mediterranean, from where only incomplete development and a negligible percentage of parasitization (Italy) have been reported. Both the host range composition and development ofL. testaceipes indicate an increase of genetic polymorphism in the established populations. Interspecific relations ofL. testaceipes and the indigenous parasitoid species indicate an increasing dominance of the exotic biocontrol agent.      

Bottom‐up effect of host plants on life‐history characteristics of Aphidoletes aphidimyza feeding on Aphis gossypii

The predatory midge Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) is widely used for the control of Aphis spp. in many agricultural systems. We aimed to determine the most suitable host plant for rearing the predatory midges on the prey Aphis gossypii Glover (Hemiptera: Aphididae). Six host plants were selected: cucumber (Cucumis sativus L. cv. Beith Alpha), tomato (Solanum lycopersicum L. cv. Falat111), eggplant (Solanum melongena L. cv. Yummy), pepper (Capsicum annuum L. cv. Bertene) (all Solanaceae), okra [Abelmoschus esculentus (L.) Moensch cv. Clemson Spineless] (Malvaceae), and squash (Cucurbita pepo L. cv. Hybrid rajai) (Cucurbitaceae). Some physical traits (length and density of trichomes) and chemical attributes (nitrogen content) of prey host plants were investigated. The results showed that prey host plants differed significantly in their effect on fitness of the predator. The shortest immature development time (18.07 ± 0.257 days), the longest female adult longevity (7.5 ± 0.18 days), and the highest fecundity (89 eggs/female) of A. aphidimyza were found with squash as prey food. The highest intrinsic rate of increase (0.171 ± 0.009 day^?1) and also the shortest mean generation time (22.4 ± 0.32 days) were also obtained when A. aphidimyza fed on A. gossypii reared on squash. Canonical correlation analysis (CCA) approved the correlation between life‐history traits of A. aphidimyza and characteristics of prey host plants. The suitability of squash for rearing A. aphidimyza can be attributed to the higher nitrogen content, longer trichomes, and relatively high density of trichomes, which provided a better environment for A. gossypii and indirectly favored A. aphidimyza. This study showed that squash is the most suitable host plant for rearing A. aphidimyza feeding on A. gossypii.     

Development and immature survival of two aphidophagous ladybirds, Coelophora biplagiata and Micraspis discolor

The developmental parameters, namely developmental periods, larval survival, adult emergence, growth index, developmental rate and sex ratio in terms of female proportion in a population of two aphidophagous ladybirds, namely, Coelophora biplagiata （Swartz） and Micraspis discolor （Fabricius） were investigated, using three aphid species as prey. The immature stages of C. biplagiata were significantly affected by prey quality and developed fastest when fed on Aphis craccivora followed by Aphis gossypii and Rhopalosiphum maidis. The order of prey suitability in terms of developmental rate of immature stages of M. discolor was just reversed. The adult females were heavier than males, while pre-pupae were heavier than pupae in both ladybirds. The sex ratio of adult emergence, though female-biased in both ladybird species, was not significantly affected by prey quality.     

Suitability of Aphis craccivora (Hemiptera: Aphididae) and Bemisia tabaci (Hemiptera: Aleyrodidae) biotype-B as prey for Chrysopa pallens (Neuroptera: Chrysopidae)

The suitability of Aphis craccivora Koch (Hemiptera: Aphididae) and Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) biotype-B eggs and nymphs as prey for pre-imaginal development and survival, adult longevity, and fecundity of the lacewing, Chrysopa pallens (Rambur) (Neuroptera: Chrysopidae) was evaluated under laboratory conditions at 25±1°C, 50±10% RH and a photoperiod of 16 h L:8 h D. Survival of C. pallens from first instar to adult eclosion was significantly different between the larvae that fed on the two prey species. C. pallens fed on A. craccivora completed development from egg to adult emergence, but those fed on eggs and nymphs of B. tabaci could not complete development, resulting in abnormal pupae and no normal adults emerged. The net reproductive rate (R ₀), intrinsic rate of natural population increase (r _m ), finite rate of increase (λ), mean generation time (T), index of population trend (I), doubling time (DT), and gross reproductive of rate (GRR) of C. pallens that fed on A. craccivora were 201.9 eggs per female, 0.13/d, 1.1/d, 40.1 d, 68.5, 5.2 d, 203.1 eggs per female, respectively. These results could be useful for mass-rearing of C. pallens and for understanding its population dynamics in the field in relation to the availability of different prey species.     

Influence of <Emphasis Type="Italic">Lecanicillium attenuatum</Emphasis> on the development and reproduction of the cotton aphid, <Emphasis Type="Italic">Aphis gossypii</Emphasis>

The activity of entomopathogens on insect pests has been investigated for many species but the influence of entomopathogenic fungi on factors other than mortality relating to population increase has not been frequently studied. The influence of Lecanicillium attenuatum CS625 (=Verticillium lecanii CS625) on development and reproduction of cotton aphid (Aphis gossypii) was investigated. A conidia suspension of the isolate was applied onto first instar nymphs. Increased spore concentration did not significantly affect each nymphal stage, total nymphal period, pre-reproductive period and the age of first larviposition. A significant dose effect on reduction of life span, reproductive period and fecundity was observed in 1st and 3rd instars after spore application. When conidia were applied to 1st instars, life span was significantly reduced to 10.8 and 8.4 days at 1 × 10⁴ and 1 × 10⁸ conidia/ml, respectively from 12.2 days in the control. During the life span, total fecundity was 41 ± 7.3, 26 ± 0.8 and 22 ± 5.7 nymphs per female at 1 × 10⁴, 1 × 10⁶ and 1 × 10⁸ conidia/ml, respectively compared with 51 ± 2.0 nymphs per untreated female. Reproduction period was also significantly shortened with increasing spore concentration. Application of spores to 3rd instars showed a similar trend. However, daily fecundity of individual aphids was not affected by spore dose. It was concluded that the isolate of L. attenuatum is able to affect populations of cotton aphid by reducing life span and total fecundity as well as by killing the aphids directly.     

Biological traits and life table parameters of variegated lady beetle, <Emphasis Type="Italic">Hippodamia variegata</Emphasis> (Coleoptera: Coccinellidae) on three aphid species

The aphidophagous ladybird beetle, Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae), is a dominant predator in various crop systems. Its life history was studied when fed on three aphid prey, viz. Aphis gossypii Glover, Aphis fabae Scopoli and Macrosiphum rosae (L.), under laboratory conditions, 25 ± 1 °C, 65 ± 5 % RH and a photoperiod of 16L:8D. The immature development period was shortest (15.2 days) when A. gossypii was used as prey and longest (18.9 days) on A. fabae. Adult coccinellids had the shortest longevity on A. fabae (64.8 days). The higher and lower mean daily fecundity was recorded for A. fabae (12.4 eggs) and M. rosae (6.2 eggs), respectively. The highest (291.0 eggs) and lowest (183.2 eggs) net reproduction rates (R ₀) were observed on A. fabae and M. rosae, respectively. Mean generation time (T) on rose aphid was significantly longer (33.4 days) than on the two other preys. The intrinsic rate of increase (r _m) was affected by the R ₀ value, and it was highest on A. fabae (0.183) and lowest on M. rosae (0.156). Based on r _m as an index of suitability of prey species, A. fabae was the most suitable prey for H. variegata. Our finding may provide basic information for developing aphid biological control programs.     

Comparison of sampling methods for alate aphids and observations on epidemiology of soybean mosaic virus in Nanjing, China

Using standard diversity indices, samples of aphids collected on a vertical net were found to be more diverse than collections from green pan traps in experiments conducted in Nanjing, China in 1981. Some species, notably Myzuspersicae, Aphis citricola, and Eriosoma (Schizoneura) japonicum, were collected in greater relative numbers in the pan traps. Several species, including the Macrosiphoniella spp., were under-represented in the green pan traps presumably because they were not attracted to the green colour of the traps. Yellow pan traps, used concurrently to monitor landing rates of economic species, caught relatively more Aphis craccivora and M. persicae and relatively fewer Aphis gossypii than green ones. In the Nanjing area soybean mosaic virus (SMV) usually spreads in spring planted soybeans during the latter half of May, causing damage. The predominant aphid species trapped at that time were M. persicae, Lipaphis erysimi, A. gossypii, A. craccivora and E. japonicum, of which the first four are known vectors. Summer planted soybeans are usually affected during a second period of virus spread occurring in mid-August when various Aphis spp. are abundant. The predominant vector of SMV at that time was thought to be Aphis glycines which colonises the crop; in 1981, however, A. citricola and A. gossypii, which do not colonise soybean and A. craccivora. which rarely colonises soybean, were much more abundant in mid-August than A. glycines. A. citricola, A. gossypii and A. craccivora are all able to transmit SMV, and thus should be considered as potentially important vectors. In infectivity assays, only four of 1040 aphids transmitted SMV. These included an A. craccivora, two Toxoptera citricidus and one Aphis sp.     

The Ability of Aphis craccivora, A. gossypii and A. citricola to Transmit Single and Mixed Viruses to Cowpeas

The ability of populations of adult apterous Aphis craccivora, A. gossypii and A. citricola to transmit the cowpea aphid-borne virus (CAMV) and cucumber mosaic virus (CMV) to cowpea was investigated. CMV was more readily transmitted than CAMV by all three aphid species, but was most readily transmitted by A. craccivora and A. citricola, with transmissions ranging from 64–71 %. With CAMV, the infection level with A. gossypii was higher than with A. craccivora and both were more efficient than A. citricola, although the differences were not significant. With mixed infections of CAMV and CMV, there was a higher level of CAMV transmission using A. craccivora from sequential feeding when CMV-infected plants were fed on first followed by CAMV-infected plants, suggesting that cowpea plants were more prone to infection by CAMV when already infected by CMV.     

Detection of potato virus Y in the aphid Myzus persicae by enzyme-linked immunosorbent assay (ELISA)

Potato virus Y was detected by enzyme linked immunosorbent assay (ELISA) in at least 50% of groups of five Myzus persicae. The mean A₄₀₅ value for groups of viruliferous aphids was 2–3 times greater than that for virus-free ones. PVY was not detected in Aphis craccivora, A. citricola or A. gossypii, three other species which transmitted the virus to peppers, and it was detected in only a small proportion of groups of Acyrthosiphon pisum. In a series of trials, success in detection of PVY by ELISA was not correlated with the ability of other aphids from the same source plant to transmit the virus to test plants. The limitation of ELISA for quantitative assay of PVY in aphids and for epidemiological work is discussed.     

Suitability of four different prey species for Dichochrysa tacta (Neuroptera: Chrysopidae)

The prey suitability for generalist insect predators is an important factor in efficient mass rearing. This work constitutes the first biological study of the predatory lacewing Dichochrysa tacta. We tested the effects of four different prey species on the biological parameters of the predatory lacewing D. tacta under laboratory conditions. These prey species consisted of Ephestia kuehniella (Zeller) and the aphids: Aphis fabae, Aphis punicae and Macrosiphum rosae. The results showed that prey species elicited a significant effect on preimaginal development times, survival, adult longevity and fecundity. In contrast, the progeny sex ratio, egg hatch and egg duration were not significantly affected by prey species. Eggs of E. kuehniella were the most suitable prey among those tested, and led to high survival rates, short development times for the preimaginal stages, long adult longevity, high fecundity, highest intrinsic rate of increase (r_m) and highest net reproductive rate (R₀) of D. tacta. Nymphs of both A. punicae and M. rosae were also relatively favourable prey, whereas nymphs of A. fabae were less suitable and resulted in reduced development, survival, adult longevity, fecundity, r_m and R₀. These results could be useful for optimising the mass rearing of D. tacta as an indigenous predator and for understanding its population dynamics in relation to different prey species in the field.     

Lethal,sublethal and transgenerational effects of the novel chiral neonicotinoid pesticide cycloxaprid on demographic and behavioral traits of Aphis gossypii (Hemiptera: Aphididae)

Aphis gossypii Glover (Hemiptera: Aphididae) is a key pest in cotton crops, notably owing to its increasing resistance to commonly used pesticides. Such resistance prompts for the development of integrated pest management (IPM) programs that include novel pesticides being effective against the aphid. In the present study, we assessed lethal and sublethal effects of cycloxaprid, a novel chiral neonicotinoid pesticide developed in China, on A. gossypii. The lethal concentration at 50% (LC₅₀) value of cycloxaprid on A. gossypii was estimated, using the dipping method, at 7.73 mg/L. The impact of a sublethal concentration (LC₁₀) and a lethal concentration (LC₄₀) of cycloxaprid on A. gossypii population growth and feeding behavior (using electrical penetration graph technique [EPG]), and its transgenerational effect were further assessed. Adult longevity and fecundity significantly decreased after exposure to LC₄₀ or LC₁₀ of cycloxaprid. Cycloxaprid with sublethal concentrations (especially LC₄₀) had negative effects on phloem ingestion by A. gossypii. Additionally, the offspring of the adults exposed to LC₄₀ of cycloxaprid had shorter nymphal development duration and adult longevity than the control, and those from LC₁₀ and LC₄₀ treatments had lower adult fecundity and net productive rate. We demonstrated that cycloxaprid is a pesticide showing both lethal and sublethal activities, and transgenerational effects on A. gossypii; it may be useful for implementation in IPM programs against this aphid pest.     

Effects of Ocimum basilicum and Ruta chalepensis hydrosols on Aphis gossypii and Tetranychus urticae

Hydrosols are by‐products derived during the extraction of essential oils and are produced in a high amount and at very low cost. Their effects on crop pests have been little studied, although recent studies have shown their insecticidal properties. In this work, the effects of hydrosols derived from Ocimum basilicum (sweet basil) and Ruta chalepensis (rue) were investigated on the serious crop pests Aphis gossypii and Tetranychus urticae. The main compounds of basil hydrosol were linalool (66.5%), eugenol (18.9%) and eucalyptol (7.1%), while rue's were 2‐nonanone and 2‐undecanone at 77.0% and 8.9%, respectively. The mortality and fecundity of A. gossypii and T. urticae were recorded for 7 days after application of hydrosols. Apterous adult aphids and female mites were sprayed on cucumber leaves in special structures. Both hydrosols caused significant mortality rates, which fluctuated between 46.0% and 64.0%. The negative control (deionized water) caused no mortality, while for the positive controls (synthetic pesticides) was 100%. The fecundity of A. gossypii and T. urticae was significantly reduced after the application of the hydrosols (17.1 nymphs of A. gossypii and 22.8 eggs for T. urticae had been produced per female after treated with the hydrosol of R. chalepensis and O. basilicum, in comparison with 41.6 and 49.5 in the negative controls, respectively). In conclusion, the hydrosols from both plants presented an important effect on the mortality and fecundity of both pests.     

Influence of vermicompost and cucumber cultivar on population growth of Aphis gossypii Glover

The melon aphid, Aphis gossypii Glover (Hem., Aphididae), is one of the most important pests of cucumber throughout the world. This aphid has a short generation time and high fecundity that result in an enormous reproductive potential, especially in cucumber‐growing greenhouses. Vermicomposts, which are produced by exploiting interactions between earthworms and microorganisms, may enhance plant growth and plant resistance against some pests and disease. In this study, the effects of vermicompost and cucumber cultivar (Cucumis sativus L.) on infestation levels with A. gossypii were evaluated. We conducted a factorial experiment with two cucumber cultivars (Royal and Storm) and five concentrations of vermicompost in the soil, including 0% (control), 10%, 20%, 30% and 50%, employing a randomized complete block design with four replicates. The experiment was conducted in a growth chamber at 25 ± 2°C, 65 ± 10% RH and a photoperiod of 14 L: 10 D h. The number of aphids was counted 3, 5, 7, 9, 12, 15, 18 and 21 days after infestation of cucumber seedlings by aphids. We found that in all vermicompost‐amended treatments, aphid numbers were lower than when plants were grown in soil without any vermicompost. The highest and lowest aphid counts occurred in the control treatment on cucumbers of the Royal cultivar and in the 30% and 50% vermicompost treatments on the storm cultivar, respectively. Overall, our study showed that the application of vermicompost has a high potential for reducing A. gossypii populations in cucumber cultures.     

Reciprocal interactions between native and introduced populations of common milkweed,Asclepias syriaca,and the specialist aphid,Aphis nerii

Following its introduction into Europe (EU), the common milkweed (Asclepias syriaca) has been free of most specialist herbivores that are present in its native North American (NA) range, except for the oleander aphid Aphis nerii. We compared EU and NA populations of A. nerii on EU and NA milkweed populations to test the hypothesis that plant–insect interactions differ on the two continents. First, we tested if herbivore performance is higher on EU plants than on NA plants, because the former have escaped most of their herbivores and have perhaps been selected for lower defence levels following introduction. Second, we compared two A. nerii lines (one from each continent) to test whether genotypic differences in the herbivore may influence species interactions in plant–herbivore communities in the context of species introductions. The NA population of A. nerii developed faster, had higher fecundity and attained higher population growth rates than the EU population. There was no overall significant continental difference in aphid resistance between the plants. However, milkweed plants from EU supported higher population growth rates and faster development of the NA line of A. nerii than plants from NA. In contrast, EU aphids showed similar (low) performance across plant populations from both continents. In a second experiment, we examined how chewing herbivores indirectly mediate interactions between milkweeds and aphids, and induced A. syriaca plants from each continent by monarch caterpillars (Danaus plexippus) to compare the resulting changes in plant quality on EU aphid performance. As specialist chewing herbivores of A. syriaca are only present in NA, we expected that plants from the two continents may affect aphid growth in different ways when they are challenged by a specialist chewing herbivore. Caterpillar induction decreased aphid developmental times on NA plants, but not on EU plants, whereas fecundity and population growth rates were unaffected by induction on both plant populations. The results show that genetic variation in the plants as well as in the herbivores can determine the outcome of plant–herbivore interactions.     

Different squash cultivars mediate performance of Aphis gossypii and its predator (Aphidoletes aphidimyza): Towards developing an IPM strategy

Different cultivars of plant species can affect the performance of aphids and their natural enemies. In this study, development and life table parameters of the cotton aphid, Aphis gossypii (Hem.: Aphididae) and its predatory midge, Aphidoletes aphidimyza (Dip.: Cecidomyiidae) were determined on four different squash cultivars (Rajaei, Elion, Clarita, and Chance) under laboratory conditions at 23 ± 2 °C, 70 ± 5% RH and 16:8 h L:D photoperiod. Adult longevity and total fecundity of A. gossypii differed with cultivar, with the highest value observed on Rajaei as the most susceptible host plant (21.93 ± 0.191 days and 74.37 ± 0.088 nymphs/female, respectively). Moreover, the intrinsic rate of increase (r) of the aphid on Rajaei and Elion (0.354 ± 0.008 day⁻¹ and 0.340 ± 0.009 day⁻¹, respectively) were significantly higher than two other cultivars. The predator reared on A. gossypii, feeding on Chance cultivar, had the lowest fecundity (51 ± 2.78 eggs/female) and the lowest r value (0.120 ± 0.011 day⁻¹) than those reared on other cultivars. These results attained from population projection estimation based on the age-stage, two-sex life table theory were in consistence with other findings which indicated the influence of different host plant cultivars on the performance of A. gossypii and its predator, A. aphidimyza. Combined use of resistant host plant cultivars together with biological control agents can be proposed as an efficient integrated pest management strategy.