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.     

Host preference by Allothrombium pulvinum (Acari: Trombidiidae) larvae on aphids: Macrosiphum rosae,Aphis gossypii and Hyalopterus amygdali (Homoptera: Aphididae)

In this study aphid-plant association and its effect on host preference of parasitic Allothrombium pulvinum larvae was examined with multiple-choice tests. Host species selection, host size selection and superparasitism with mite larvae were studied with two-choice tests. Three aphid species were used: Macrosiphum rosae, Aphis gossypii and Hyalopterus amygdali. In multiple-choice tests, larvae of A. pulvinum showed no significant preference for any aphid-plant association when given M. rosae on rose, A. gossypii on cucumber and H. amygdali on apricot simultaneously. Two-choice tests showed that larval mites preferred H. amygdali to A. gossypii, but had no preference when offered a choice between A. gossypii and M. rosae or between H. amygdali and M. rosae. In host size selection and superparasitism tests, significantly more mites selected the larger host (M. rosae). Furthermore, parasitised H. amygdali were preferred to unparasitised ones. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of prey species on immature survival, development, predation and reproduction of Coccinella transversalis Fabricius (Col., Coccinellidae)

Six aphid species, viz. Aphis craccivora, Aphis gossypii, Aphis nerii, Myzus persicae, Lipaphis erysimi and Uroleucon compositae were provided as prey to the feeding stages of Coccinella transversalis (Fabricius). All of them were found to be essential prey, however the relative prey suitability varied. All the predatory stages of C. transversalis consumed and preferred A. gossypii, the most and A. nerii, the least. Significant effect of prey quality was observed on pre‐imaginal developmental periods, wet weights and adult longevity. The complete development was shortest on A. gossypii (13.01 ± 0.18 days) and longest on A. nerii (20.51 ± 0.25 days). The total prey consumption by larva, adult male and female in their lifetime was maximum (665.30 ± 5.75, 4831.10 ± 123.54 and 5412.30 ± 94.51, respectively) on A. gossypii and minimum (434.80 ± 4.03, 802.80 ± 34.37 and 905.20 ± 52.48, respectively) on A. nerii. Immature survival, growth index and adult emergence of C. transversalis was maximum (68.33, 7.82 and 88.21%, respectively) when larval instars consumed A. gossypii and minimum (37.75, 2.18 and 60.69%, respectively) after feeding on A. nerii. Female reproduction was also prey quality dependent showing maximum reproductive performance in terms of fecundity and percentage viability, with a highest reproductive period and lowest non‐reproductive period on A. gossypii, followed by A. craccivora, L. erysimi, M. persicae, U. compositae and A. nerii. Regression analysis revealed a positive correlation between: (1) daily prey consumption and relative growth rate, (2) adult weight and developmental rate, (3) weights of adult male and female, and (4) female longevity and fecundity.     

Influence of intraguild predation between Episyrphus balteatus and Hippodamia variegata on their prey

Intraguild predation (IGP) is an interaction that frequently occurs in natural enemy communities, especially aphidophagous predators. This research investigated IGP intensity between Episyrphus balteatus De Geer (Diptera: Syrphidae), with Hippodamia variegata Goeze (Coleoptera: Coccinellidae). Five predator combinations including second and third larvae of H. variegata and third instar larvae of E. balteatus plus control treatment (totally six treatments) were tested. The effect of IGP on cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) population density was investigated on sweet pepper seedlings under laboratory microcosms. In most combinations, the third instar larvae of E. balteatus alone reduced an A. gossypii population more efficiently than ladybird larvae and their combinations. Furthermore, IGP between third instar of E. balteatus and second larvae of H. variegata was asymmetrical; second instar H. variegata larvae were always the intraguild prey for third instar E. balteatus. The obtained result showed that outcome of IGP interaction on cotton aphid density was non-additive.     

Two Anthocoris bugs as predators of glasshouse aphids – voracity and prey preference

Voracity and prey preference were evaluated for adult females of the predatory bugs Anthocoris nemorum (L.) and Anthocoris nemoralis (Fabricius) (Heteroptera: Anthocoridae) preying upon five species of aphids (Homoptera: Aphididae), of which Myzus persicae Sulzer, Aulacorthum solani (Kaltenbach), Macrosiphum euphorbiae (Thomas), and Aphis gossypii Glover are common pests in Danish glasshouse crops. Aphis fabae Scopoli was included to determine the influence of food quality on the preference of the predators, since A. fabae has proved to be of poor nutritional value to Anthocoris spp. The experiments were carried out over 24 h in climate cabinets at 20 °C, 60–70% r.h., L18:D6. The aphids were offered in equal amounts in combinations of two species in instars of comparable size. Myzus persicae served as a reference species in all combinations. Both predators accepted all five species of aphids as prey. The numbers of aphids killed per 24 h period varied between 3.7 and 18.0 for A. nemorum and between 3.6 and 12.7 for A. nemoralis. Field collected A. nemorum females, presumably in a state of reproductive diapause, killed in three of four prey combinations significantly more aphids than did ovipositing A. nemoralis females which originated from a commercial rearing. When A. nemorum females had terminated their reproductive diapause and commenced oviposition, voracity increased approximately threefold. When prey preferences were evaluated as a total number of killed prey, no difference in preference was found between the two Anthocoris species. Both predatory bugs preferred M. persicae to the other species, the most accepted alternative prey were A. gossypii, A. fabae, A. solani, and M. euphorbiae, in descending order. However, evaluating preference by number of aphids consumed, A. nemoralis showed a more pronounced preference for M. persicae, especially when combined with A. fabae. In nearly every case, A. nemoralis rejected A. fabae as a food item after killing the aphid. Thus, A. nemoralis exhibited a more specific food choice than A. nemorum. By killing and consuming different aphid species found in glasshouse crops – particularly M. persicae– both A. nemorum and A. nemoralis showed preliminary qualities as agents for the biological control of aphids.     

Cucumber mosaic virus epidemiology in pepper: Aphid dispersal,transmission efficiency and vector pressure

Cucumber mosaic virus (CMV) causes significant damage and yield losses in peppers. The objective of this study is to determine the efficiency of prevalent aphid species occurring in pepper fields to transmit this virus within pepper plants and to identify their vector pressure in order to target the critical species implicated in CMV epidemics spread. Alatae and apterae were monitored in an experimental pepper field in northern Tunisia for 3 years. Sixty-eight species were captured in winged form in yellow water traps. The most abundant species were Myzus persicae, Aphis gossypii, Aphis fabae, Aphis spiraecola, Acyrthosiphon pisum, Metopolophium dirhodum, Rhopalosiphum maidis, Aphis craccivora, Aphis nerii, Hyalopterus pruni, Sitobion avenae and Rhopalosiphum padi constituting 90% of aphid populations in the field. Their temporal dynamic showed a high period of flight activity from April to June and a second peak in September was registered. Two of these species, M. persicae and A. gossypii were also found in their wingless form on pepper leaves with a prevalence of 99.5% and 0.5%, respectively. The 12 most abundant aphid species were tested for their transmission efficiency of CMV (CMV-pepp2 isolate) with A. gossypii as a reference vector. All aphids tested, including colonizing and non-colonizing species on pepper, were verified to be vectors of this isolate. However, significant differences in the transmission efficiency were found between the aphid species (p < .001, SE = 7.29). M. persicae (60%) scored the highest transmission efficiency rate. Additionally, A. fabae solanella (50%) had higher transmission efficiency than the reference vector, A. gossypii (40%). H. pruni (16.67%) was documented as a new CMV vector to pepper. The single-aphid transmission probabilities ranged from 0.7% to 16.7%. The calculated mean Vector Pressure Index (VPI) for these 12 species showed a stronger relationship with the specific aphid population variance (R = 0.89, p < .01) than the variation of the specific single-aphid transmission probabilities (R = 0.62, p < .05). Indeed, for alate non-colonizer vectors, A. spiraecola has recorded the highest mean VPI (27.5), despite its moderate transmission efficiency (23.33%). Nevertheless, for colonizer vectors in both winged and wingless forms, M. persicae had the highest mean VPI (49.26) of all vector species and was mostly present in its apterous form. The 12 vector species contributed to a total mean VPI of 133.48 during the surveyed periods. This research determined key features of CMV epidemiology in pepper crops that might be helpful for CMV disease management at an early stage.     

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.     

Prey‐mediated changes in the selectivity of the predator Macrolophus pygmaeus (Heteroptera: Miridae)

When foraging in communities with mixed prey, generalist predators may be confronted with prey species that differ in quality, size and mobility and interact with one another. To examine prey selection, predation by Macrolophus pygmaeus (Heteroptera: Miridae) was recorded by providing a diet of either one or two prey species of Myzus persicae (third‐instar nymphs), Aphis gossypii (fourth‐instar nymphs), Trialeurodes vaporariorum (third‐instar nymphs) and Ephestia kuehniella (eggs). In the experiments, prey mobility, prey quality and prey biomass were considered. The biomass consumed by the predator was dependent on the combination of prey species and the quantity of biomass offered. In choice experiments with diets mixed of two prey species at equal densities, the predation to A. gossypii was significantly reduced in the presence of E. kuehniella but the rate of consumption of M. persicae, T. vaporariorum and E.kuehniella was not significantly affected by the coexistence of any other species in the mixed prey diet. When equal amounts of biomass from two prey species were provided in combination, the total consumed biomass was significantly reduced in the mixed prey diets composed of E. kuehniella eggs and aphid nymphs. Thus, under the mixed‐prey situation, prey selection by predators may be affected by interactions among prey species differing in traits such as quality, mobility and size.     

Transmission of Zucchini yellow mosaic virus by Colonizing and Non-colonizing Aphids in Greece and New Aphid Species Vectors of the Virus

Nineteen aphid species were tested for their ability to transmit Zucchini yellow mosaic virus (ZYMV) from and to zucchini under laboratory conditions. Sixteen species were found to be new vectors of ZYMV (i.e. Aphis craccae, Aphis fabae, Aphis nerii, Aulacorthum solani, Brachycaudus cardui, Brevicoryne brassicae, Hyalopterus pruni complex, Hyperomyzus lactucae, Macrosiphoniella sanborni, Macrosiphum rosae, Metopolophium dirhodum, Myzus cerasi, Rhopalosiphum maidis, R. padi, Semiaphis dauci and Sipha maydis). Their transmission efficiency by a single aphid was low (0.1–4.2%). Myzus persicae was used as a control and was the most efficient vector (41.1%, one aphid per plant). Hayhurstia atriplicis, Myzus ascalonicus and Sitobion avenae did not transmit the virus. In four out of six new vectors assayed in arena tests for propensity estimation, propensity was higher than efficiency. Data from an experimental zucchini field in northern Greece revealed a high correlation between ZYMV spread and alatae of the vector species. The most abundant aphid vectors during 2 years experimentation were M. persicae, Aphis gossypii and Aphis spiraecola. The possible role of the 16 new and the previously known aphid vectors in the epidemiology of ZYMV was investigated using data of transmission efficiency combined with the captures of their alatae in the Greek net of a Rothamsted type suction trap.     

Individual variation in oviposition preference, and its interaction with larval performance in an insect predator

Individual female Episyrphus balteatus (DeGeer) (Diptera: Syrphidae) show different oviposition preferences when presented with two aphid prey species, Aphis sambuci L. and A. fabae (Scop). After larvae were reared on those aphids, some fitness components indicated that individual females were adapted to different host-use strategies, with preference for one aphid prey species entailing a trade-off in poorer performance on another. We interpret the pattern of significant interactions as suggesting that natural selection has responded to the nutritional value of prey. Received: 11 September 1998 / Accepted: 16 November 1998     

Feeding behavior of aphids on narrow‐leafed lupin (Lupinus angustifolius) genotypes varying in the content of quinolizidine alkaloids

Since the beginning of breeding narrow‐leafed lupins [Lupinus angustifolius L. (Fabaceae)] with a low alkaloid content, susceptibility to several aphid species has increased. Therefore, the probing and feeding behavior of Aphis fabae Scopoli, Aphis craccivora Koch, Acyrthosiphon pisum (Harris), Myzus persicae (Sulzer), and the well‐adapted Macrosiphum albifrons Essig (all Hemiptera: Aphididae) was studied over 12 h on narrow‐leafed lupin genotypes containing varying amounts and compositions of alkaloids. We used the electrical penetration graph (EPG) technique to obtain information on the influence of alkaloid content and composition on the susceptibility to various aphid species. Results indicated that the total time of probing of A. fabae, A. craccivora, A. pisum, and M. persicae increased with a reduced alkaloid content, whereas the alkaloid content had no influence on M. albifrons. Almost all of the individuals (>93%) conducted sieve element phases on the highly susceptible genotype Bo083521AR (low alkaloid content). A reduced occurrence of phloem phases was observed during the 12‐h recording on the alkaloid‐rich cultivar Azuro, especially for A. pisum (37.5%) and A. fabae (55.0%). Furthermore, aphids feeding on genotypes with low alkaloid content had in most cases significantly longer sieve element phases than when feeding on resistant genotypes (Kalya: low alkaloid content, yet resistant; Azuro: high alkaloid content, resistant), whereas M. albifrons showed the longest phloem phase on the alkaloid‐rich cultivar Azuro. As most significant differences were found in phloem‐related parameters, it is likely that the most important plant factors influencing aphid probing and feeding behavior are localized in the sieve elements. The aphids’ feeding behavior on the cultivar Kalya, with a low alkaloid content but reduced susceptibility, indicates that not only the total alkaloid content influences the feeding behavior but additional plant factors have an impact.     

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.     

The effects of different aphid foods on Adalia bipunctata L. and Coccinella 7-punctata L

The influence of different aphid foods on larval development and adult fecundity of Adalia bipunctata L. and Coccinella 7-punctata L. was investigated. Certain aphids such as Myzus persicae Sulz. and Acyrthosiphon pisum Harris were suitable for both species. Megoura viciae Buckt., was toxic to A. bipunctata but not to C. 7-punctata. Aphis fabae Scop., although a common natural prey of A. bipunctata, slowed larval development, partly because it was nutritionally unsuitable. Fecundity of adults fed on A. fabae was also reduced to less than half. Larvae and adults of C. 7-punctata developed and reproduced as well on A. fabae as on other suitable aphids. C. 7-punctata caught aphids more quickly than A. bipunctata. Larvae of both species given relatively unsuitable prey fed more slowly than normal and consumed less of each aphid. The toxic aphid M. viciae was rejected by A. bipunctata after a short period of feeding.     

Life history characteristics of Orius insidiosus (Say) fed Aphis glycines Matsumura

The soybean aphid, Aphis glycines Matsumura, is a new invasive pest of soybeans throughout most of the soybean production areas of North America. Field studies have demonstrated that the indigenous predator, Orius insidiosus (Say), is an important natural enemy of the soybean aphid early the soybean crop season. Because soybean aphid is newly introduced into North America, the life history characteristics of predators fed this aphid are not known. In laboratory assays, we measured the survival, development, longevity and reproduction of O. insidiosus fed 1, 3, 6 or 12 seconds to third instars of soybean aphid. O. insidiosus nymphal development decreased from 34.0 to 21.4 days as the number of soybean aphid nymphs provided increased from 1 to 6 aphid nymphs daily. Stage-specific mortality was highest at 68% for first instar O. insidiosus nymphs fed 1 soybean aphid nymph per day. Adult longevity (43.9 days) and fecundity (49.7 eggs per female) was highest for O. insidiosus fed 6 soybean aphid nymphs daily, but longevity (23.5 days) and fecundity (10.1 eggs per female) declined for adults fed 1 soybean aphid nymph daily. The intrinsic rate of increase of O. insidiosus ranged from 0.048 to 0.133. Compared to other prey species, soybean aphid is an adequate prey item for O. insidiosus. Our results suggest that O. insidiosus will be most effective in suppressing soybean aphid population growth in the initial phase of the aphid’s colonization of soybeans.     

Foraging responses of Coccinella septempunctata,Hippodamia variegata and Chrysoperla carnea to changing in density of two aphid species

The successful use of predators in classical biocontrol programmes needs several background laboratory investigations, one of which is the evaluation of predator behavioural responses to changes in the density of their prey. The impact effect of the density of two prey species [Myzus persicae Sulzer and Aphis craccivora Koch (Hemiptera: Aphididae)] on the predation rates of third-instar Chrysoperla carnea Stephens (Chrysopidae: Neuroptera) and fourth-instar Coccinella septempunctata L. and Hippodamia variegata Goeze (Coccinellidae: Coleoptera) larvae was studied. Although prey species, predator species, prey density, and their interactions all had significant effects on the numbers of aphids consumed, the type of functional response did not vary, remaining a type II response in all treatments. However, the type II parameters differed among predator species on the same prey species, and for each predator species on the two prey species. Chrysoperla. carnea on M. persicae and H. variegata on A. craccivora were more voracious than other predators. In the context of functional response and biological control, the release of these predators, that show inverse density-dependent mortality, has to be started in early season to build up their population on low aphid densities and attack later high aphid populations.     

Responses of Episyrphus balteatus DeGeer (Diptera: Syrphidae) in relation to prey density and predator size

Laboratory experiments were conducted to determine the functional and numerical responses of the aphidophagous hover fly Episyrphus balteatus DeGeer (Diptera: Syrphidae) to different densities of 4th instar black bean aphids, Aphis fabae Scopoli (Homoptera: Aphididae), on broad bean, Vicia faba L. (Fabaceae). Two different-sized larvae of predators were tested in different densities of similar-sized prey to determine whether functional response parameters depended on the body sizes of predator and prey. In numerical response experiments, gravid E. balteatus females were exposed individually to different densities of 4th instars of A. fabae on cut sections of the broad bean plant, V. faba L. Logistic regression suggested a type II functional response for both larval sizes of E. balteatus. The searching efficiency (a) of the larger larvae was higher than that of the smaller ones. Prey consumption was higher, and handling time (T_h) was lower for larger larvae than smaller ones. The theoretical maximum number of A. fabae nymphs eaten by the different-sized larvae was 125 and 269 nymphs per day. Larger E. balteatus larvae are more efficient predators for aphid management strategies. The reproductive numerical response, in terms of the number of eggs laid, increased curvilinearly with increasing prey density, but the proportion of eggs laid (egg number/prey density) decreased as the initial density of prey increased.     

Role of leaf glandular trichomes of melon plants in deterrence of Aphis gossypii Glover

External characteristics of the leaf epidermis and their effects on behaviour of Aphis gossypii Glover were evaluated in two Cucumis melo L. genotypes, ‘Bola de Oro’ (aphid susceptible) and TGR‐1551 (aphid resistant) in order to explore their role in the early rejection of TGR‐1551 by this aphid. No differential effects of epicuticular waxes on aphid behaviour were observed. The type, distribution and number of trichomes on melon leaves were also studied. Pubescence in melon, measured as the number of non‐glandular trichomes per cm², was not sufficient to prevent aphid settling. However, there was a high density of type I glandular trichomes on leaves of the aphid‐resistant genotype. According to microscopic observations and stain testing, these trichomes store and secrete phenols and flavonoids. Free‐choice tests were conducted to determine the effect of these glandular trichomes on A. gossypii preference, revealing that aphids reject leaf disks of TGR‐1551 from the onset of the experiment. Additional experiments after removal of leaf type I glandular trichome exudates showed that A. gossypii preferred washed TGR‐1551 leaf disks over unwashed disks, while this effect was not observed in experiments using washed and unwashed ‘Bola de Oro’ leaf disks. These results suggest that a high density of glandular trichomes and chemicals secreted by them deter A. gossypii and disturb aphid settling on TGR‐1551.     

Effects of predation pressure and prey density on short-term indirect interactions between two prey species that share a common predator

1. Generalist predators are important contributors to reliable conservation biological control. Indirect interactions between prey species that share a common generalist predator can influence both community dynamics and the efficacy of biological control. 2. Laboratory cage experiments investigated the impact of the combined consumptive and non-consumptive effects of predation by adult Hippodamia convergens as a shared predator on the population growth and relative abundance of Acyrthosiphon pisum and Aphis gossypii as prey species. Predation pressure and prey density were varied. 3. At low predation pressure the indirect interaction between aphid species was asymmetrical with a proportionally greater negative impact of predation on A. gossypii than on A. pisum. At intermediate predation pressure, the indirect interaction became symmetrical. At high predation pressure and higher levels of prey density, it was asymmetrical with greater negative impact on A. pisum, often driven to local extinction while A. gossypii populations persisted. 4. A linear mixed-effects model including early population growth of both aphid species and predation pressure explained 96% and 92% of the variation in the population growth of A. pisum and A. gossypii, respectively, over an 8-day period. The overall effect of shared predation on the indirect interaction between the two aphid species is best described as apparent commensalism, where A. pisum benefited from early population growth of A. gossypii, while A. gossypii was unaffected by early population growth of A. pisum. Considering these indirect interactions is important for conservation biological control efforts to be successful.     

Suitability of Aphis fabae, Myzus persicae (Homoptera: Aphididae) and Aleyrodes proletella (Homoptera: Aleyrodidae) as prey for Coccinella undecimpunctata (Coleoptera: Coccinellidae)

The suitability of Aphis fabae Scopoli, Myzus persicae Sulzer and Aleyrodes proletella L. as food sources for Coccinella undecimpunctata L. was evaluated by studying the impact of prey consumption on the predator’s population growth parameters and feeding parameters. Unlike A. proletella, A. fabae and M. persicae supported the development and reproduction of C. undecimpunctata. A. fabae and M. persicae were considered to be essential prey, whereas A. proletella was considered to be an alternative prey. Aphid species showed different degrees of suitability: M. persicae significantly decreased the pre-oviposition period and increased adult longevity, fecundity and fertility compared with A. fabae. Moreover, A. fabae represents a suitable diet for larval development, but is not a suitable food source for adult reproduction. The predator’s population growth parameters, R₀, r_m and λ were increased with M. persicae, whereas T decreased. We found that the 4th instar larvae were the most voracious, particularly when fed on M. persicae; nevertheless, with this prey daily weight gain and feeding efficiency of 4th instar larvae were similar to that of individuals fed with A. fabae.     

Abundance and biological parameters of psyllophagous coccinellids in pistachio orchards

The abundance of coccinellids on pistachio trees was monitored at both a cultivated pistachio plantation and a wild pistachio growing area in Rafsanjan, Iran. Eleven ladybird species were identified from planted pistachio trees with Adalia bipunctata (Linnaeus) and Oenopia conglobata contaminata (Menetries) the most abundant ladybirds. At the wild pistachio plantation site, 17 coccinellid species were collected, with Brumus undulatus Weise the most abundant ladybird, followed by A. bipunctata and O. conglobata contaminata. Three species of Coccinellidae were evaluated for their potential for biological control of the common pistachio psylla (CPP), Agonoscena pistaciae Burckhardt and Lauterer. Coccinella undecimpunctata aegyptica (Reiche), Exochomus nigripennis (Erichson) and Hippodamia variegata (Goeze) developed successfully on A. pistaciae nymphs and reproduced successfully. Development and reproduction of these ladybirds were also examined on an alternative prey, the cotton aphid Aphis gossypii Glover, the most abundant aphid species on herbal weeds in pistachio orchards. The highest intrinsic rate of natural increase (r_m value) was observed in C. undecimpunctata aegyptica, 0.22 and 0.23 when it was fed on A. pistaciae and A. gossypii Glover, respectively. In comparison, the lowest r_m values (0.12 and 0.13) were found in E. nigripennis on the CPP and cotton aphid diets, respectively. Exochomus nigripennis consumed the largest number of psyllid nymphs during larval period, while the adults consumed the lowest number of psyllid nymphs daily. Although eight psyllophagous coccinellid species were collected in colonies of the CPP on pistachio trees, they did not regulate psyllid numbers below damaging levels. At present, conservation should assume a central role in biological control strategies for this pest.