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1.
    
Interactions between natural enemies can be crucial for determining their overall control of pest species, yet the mechanisms that govern such interactions are often poorly understood. The risk of negative effects such as intraguild predation and the possibility of mitigating such risks are important components for ultimately determining the compatibility of biological control agents. We performed a group of experiments to determine whether the coccinellid Harmonia axyridis Pallas (Coleoptera: Coccinellidae) poses an intraguild threat to the parasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae) and to see whether A. ervi is able to avoid predation by responding to the chemical tracks deposited by H. axyridis. We show that although H. axyridis does not readily consume A. ervi mummies, it preferentially consumes parasitized aphids over unparasitized aphids. We also show that A. ervi can defend against this threat by avoiding oviposition in the presence of H. axyridis chemical tracks. Aphidius ervi parasitized far fewer pea aphids Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae) on plants [Vicia faba L. (Fabaceae)] with H. axyridis chemical tracks in a no‐choice environment at a single‐plant scale. Similarly, when parasitoids could move freely between plants with and without tracks, A. ervi parasitism was higher on plants without tracks. Behavioral observations of A. ervi foraging suggested that this might be because of reduced A. ervi attack rates and patch residence times in the presence of H. axyridis tracks. Despite a risk of intraguild predation by H. axyridis, our study suggests that A. ervi may be able to mitigate this risk by altering its behavior in response to chemical cues.  相似文献   

2.
    
Biological control of economically important crop pests is an important component of integrated pest management (IPM) strategies. Predator–prey energy relationships are critical to the success of biocontrol strategies; however, these relationships are often ignored in many IPM programs. In this study, the biocontrol potential of cotton aphid, Aphis gossypii (Glover) (Hemiptera: Aphididae), by the ladybeetle Propylaea japonica (Thunberg) (Coleoptera: Coccinellidae) was estimated in terms of energy budgets calculated at 27 ± 1 °C. The energy equivalent of prey subjects (aphids) consumed was estimated from bomb calorimetry and partitioned into the energy associated with ingestion, assimilation, respiration, reproduction, and waste for each developmental stage of the lady beetle. The average assimilation efficiencies for larval and adult ladybeetles were 88.2 and 91.1%, respectively, whereas net ecological efficiencies were 17.6% for larvae and 2.6% for adults. Similarly, assimilation efficiencies of cotton aphids were 71.5 and 74.4% for nymphs and adults, respectively. Based on energy budget calculations, approximately 520, 3‐day‐old aphids and 5 356, 3‐day‐old aphids were estimated to be consumed by the ladybeetle larval stage and the female adult stage, respectively. These estimates were similar to the actual number of aphids consumed by the ladybeetles, based on actual counts. The current data demonstrate that P. japonica is an important natural enemy of the cotton aphid, and that predator–prey energy relationships can play a critical role in biocontrol strategies and IPM programs.  相似文献   

3.
    
Transgenic Bacillus thuringiensis Berliner (Bt) crops receive particular attention because they carry genes encoding insecticidal proteins that might negatively affect non‐target arthropods. Here, laboratory experiments were conducted to evaluate the impact of Cry1Ab‐expressing transgenic maize [5422Bt1 (event Bt11) and 5422CBCL (MON810)] on the biological parameters of two non‐target arthropods, the aphid Rhopalosiphum maidis (Fitch) (Hemiptera: Aphididae) and its predator the ladybeetle Propylea japonica (Thunberg) (Coleoptera: Coccinellidae). In a long‐term assay (three generations), no significant differences were found between R. maidis fed Bt maize and those fed a near‐isogenic line (5422) when individual parameters were compared, including nymph development time, adult longevity, aphid spawning period, and fecundity. No negative effects were detected throughout the life cycle of P. japonica in aphids’ feeding amount, development (nymphs, pupae, adults, and progeny eggs), fecundity, or egg hatching when they preyed on Bt maize‐fed aphids compared with non‐Bt maize treatments. A tritrophic assay revealed that Cry1Ab was highly diluted through the food chain (Bt maize leaves, R. maidis, and P. japonica), as detected by an enzyme‐linked immunosorbent assay (ELISA). In conclusion, although Cry1Ab concentrations in maize leaves increased as the plants developed, Cry1Ab levels were significantly reduced in the aphid R. maidis, and no traces of Cry1Ab were detected in P. japonica preying on Bt maize‐fed aphids. The two hybrids of Bt maize expressing Cry1Ab had no negative effects on the measured biological parameters of the aphid R. maidis or its predator, the ladybeetle P. japonica.  相似文献   

4.
    
Environmental heterogeneity can have profound effects on agroecosystem function and it is important for improving ecosystem services such as biological control. Promoting system diversity via non‐crop plants is one method for increasing habitat heterogeneity within farmscapes. Non‐crop plants provide access to refuges and alternative food resources provide multiple benefits to enhance populations of arthropod predators. In this study, we examined the effects of small‐scale spatial structure on life‐stage specific interactions between the native coccinellid, Hippodamia convergensGuérin‐Méneville, and the exotic Harmonia axyridis (Pallas) (both Coleoptera: Coccinellidae), which overlap in spatial distribution in many crop systems. Squash [Cucurbita pepo L. (Cucurbitaceae)] and non‐crop mugwort [Artemisia vulgaris L. (Asteraceae)] plants with and without aphids were used as a model of spatial heterogeneity in micro‐ and mesocosm experiments. In response to factorial treatment combinations, we evaluated oviposition behavior, egg predation, larval survival, and larval predator‐prey and predator‐predator interactions. Adult H. convergens displayed higher foraging activity on aphids when exposed to complex habitats containing a non‐crop plant. In the presence of the exotic coccinellid, H. convergens preferred to deposit eggs on the non‐crop plant. Furthermore, a combination of spatial heterogeneity and prey availability reduced larval intraguild predation and cannibalism, and improved reproductive output of H. convergens by reducing intra‐ and interspecific egg predation. Our results provide evidence that life‐stage‐specific intraguild interactions are mediated by access to non‐crop plants. Thus, the introduction or maintenance of non‐crop plants has the potential to enhance coexistence of multiple natural enemies and improve top‐down control of pests.  相似文献   

5.
    
The selection of a host of high nutritional quality is of great importance to the development of offspring of larvipositing aphids, as is the avoidance of natural enemies. Little is known, however, about their ability to select host plants based on these factors. This article tests the preference of aphids Sitobion avenae (Fabricius) and Rhopalosiphum padi (L.) (both Hemiptera: Aphididae) for different winter wheat cultivars, Triticum aestivum (L.) (Poaceae), and their ability to detect and avoid predators in sacrifice of their most preferred host. In both species a preference was observed for nutritionally superior hosts. The preference of both species then exhibited a change towards a nutritionally inferior host after infestations of the harlequin ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), that had been consuming conspecific aphids. This investigation opens the door to the interesting prospect of the ability of aphids to make complex decisions regarding a compromise between high‐quality nutrition and avoidance of predation.  相似文献   

6.
    
Several models and experimental studies conducted in confined environments have shown that intraguild predation (IGP) can modulate population abundances and structure communities. A number of ecological and abiotic factors determine the nature and frequency of IGP. This study examined the effect of plant architecture and extraguild prey density, and their interactions, on the occurrence of IGP between two species of ladybird, Harmonia axyridis (Pallas) and Propylea quatuordecimpunctata L. (both Coleoptera: Coccinellidae). Theoretical concepts predict that IGP levels would increase with a decrease of both extraguild prey density and plant structural complexity. We conducted a factorial experiment in an open soybean field into which coccinellid larvae were introduced in experimental plots for a period of 5 days. We tested two levels of soybean aphid [Aphis glycines Matsumara (Hemiptera: Aphididae)] density, low and high (100 and 1 000 aphids per plot, respectively), and two levels of plant complexity, low (by removing half of the branches from the soybean plants) and high (by leaving plants intact). We used species‐specific molecular markers to detect the presence of P. quatuordecimpunctata in the digestive tract of H. axyridis. Molecular gut‐content analysis of H. axyridis revealed that rates of IGP were higher (20%) at low aphid density than at high aphid density (<6%). Decreased plant complexity did not impact the frequency of IGP. In accordance with existing literature, this study demonstrates that IGP is amplified at low extraguild prey density. We conclude that considering environmental factors, such as extraguild prey density, is crucial to improve our ability to predict the impact of intraguild predation on community structure and, from an applied perspective, biological control.  相似文献   

7.
    
Cannibalism (CANN) and intraguild predation (IGP) may provide energy and nutrients to individuals and eliminate potential competitors. These negative competitive interactions could also affect the coexistence of predatory species. The co‐occurrence of aphidophagous ladybird species in crops creates opportunities for CANN and IGP, especially when aphids become scarce. The Lotka–Volterra model predicts the coexistence of two species if intraspecific competition is stronger than interspecific interference interactions. Cycloneda sanguinea L. and Eriopis connexa (Germar) (both Coleoptera: Coccinellidae) coexist in sweet pepper crops in La Plata (Argentina) consuming mainly Myzus persicae (Sulzer) (Hemiptera: Aphididae). The present study used laboratory experiments to estimate levels of CANN and IGP by adults and larvae on eggs, and by adults on larvae, in both the presence and absence of prey (i.e., M. persicae), to explain the effect of prey on coexistence of these two predators. Levels of CANN by C. sanguinea and E. connexa were high in the absence of aphids, and decreased when prey was present. Intraguild predation was bidirectional and asymmetric. Adults and larvae of E. connexa were more voracious IG predators of C. sanguinea than vice versa, the former being the stronger IG predator and interference competitor. Eriopis connexa always won when larvae of the same instar were compared, whereas the larger larva always won when larvae were of different instars, regardless of species. In the presence of prey, CANN by both species decreased, but IGP by E. connexa on C. sanguinea remained high, suggesting that E. connexa could displace C. sanguinea via interspecific interference competition. Other factors potentially affecting the coexistence of C. sanguinea and E. connexa in sweet pepper crops are discussed.  相似文献   

8.
    
Thiamethoxam (TMX) is one of the most effective neonicotinoid insecticides for the control of green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), and various side effects can be expected in its natural enemies. The multicolored Asian lady beetle or harlequin ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is an important predator against M. persicae in greenhouses and fields. In this study, we evaluated the toxicity of TMX to H. axyridis and the effect on the functional response of this predator to M. persicae through three routes of exposure. Acute toxicity bioassays indicated that LC50 values of TMX on H. axyridis through direct residual contact (‘contact’), systemic application (‘systemic’), and leaf‐dip treatment (‘leaf‐dip’) were 18.99, 21.26, and 15.39 mg a.i. l?1, respectively. The hazard quotient indicated a potential hazard of this agrochemical regardless of the exposure routes. The mortality caused by the lowest rate, 2 mg a.i. l?1, was not significantly different compared with the control group. For the three routes of sublethal TMX exposure, the type‐II functional response was a good fit to the prey consumption of H. axyridis. Predation was most affected by leaf‐dip treatment, followed by contact and systemic treatments, which had similar effect. For all exposure routes, the predation capacity of the predator recovered quickly after transfer to untreated cabbage leaves. Thiamethoxam applied systemically was the least toxic to H. axyridis and did not affect the functional response of the predator. However, the sublethal effects of TMX through both contact and leaf‐dip application may reduce the population growth of H. axyridis and consequently impair the biological control of M. persicae by this predator. These results illustrate that the assessment of potential effects of TMX on H. axyridis is crucial to develop effective integrated pest management programs for M. persicae in China.  相似文献   

9.
    
Under natural conditions, generalist predatory insects have to cope with a variety of potential prey species that are not all equally suitable. Under these circumstances, learning may be adaptive if it allows adjustment to variations in resource quality and availability. Under laboratory conditions, we examined the learning ability and memory in the prey selection process of larvae of the predatory coccinellid Coleomegilla maculata ssp. lengi Timberlake (Coleoptera: Coccinellidae). Using choice tests, we studied prey rejection behaviour of C. maculata fourth instars towards prey of different quality and we also tested the influence of hunger and prior experience with other food types on the prey rejection behaviour of coccinellid larvae. Coleomegilla maculata larvae gradually changed their behaviour and rejected low‐quality hosts more frequently, whereas high‐quality hosts were nearly always accepted. After 48 h, the learned behaviour appeared to be partially forgotten. Hunger and experience with other food types prior to the test had little effect on the gradual change of behaviour but the quality of the food ingested influenced the initial level of prey rejection. Our results demonstrate that (1) C. maculata larvae can adjust their prey selection behaviour with experience to reject progressively less suitable prey, and (2) previous experience with other prey types can influence their initial preference.  相似文献   

10.
    
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11.
    
Host‐associated differentiation (HAD) is the formation of genetically distinct, host‐associated populations created and maintained by ecologically mediated reproductive isolation. HAD potentially accounts for species origins in parasites, including herbivorous insects. Although case studies testing the occurrence of HAD are accumulating, it is still unclear how common HAD is and which specific ecological traits explain its occurrence. To address these issues, studies are needed that include negative results (i.e., instances in which parasite populations do not exhibit HAD) and test for HAD across communities (i.e., several parasite species on the same set of host species). In this study, HAD was tested in a community of six species of Aphidomorpha (Hemiptera) that share a host‐plant pair: pecan [Carya illinoinensis (Wangenh.) K.Koch] and water hickory [Carya aquatica (F.Michx) Nutt., both Juglandaceae] trees. All six species are parthenogenetic and three species are endophagous, traits that can exacerbate host‐specific selection. AFLP markers were employed to detect the presence of genetically distinct, host‐associated populations for each insect species. Strict HAD (i.e., the occurrence of genetically distinct pecan‐associated and water hickory‐associated genotypes) was found in Phylloxera notabilis Pergande (Phylloxeridae), Phylloxera devastatrix Pergande, and Monelliopsis pecanis Bissel (Aphididae). Monellia caryella Fitch (Aphididae) displayed a pattern of partial HAD (i.e., the occurrence of only a genetically distinct pecan‐associated genotype). No HAD was found in Melanocallis caryaefoliae Davis (Aphididae) or Phylloxera texana Stoetzel. The pattern of HAD occurrence in the pecan and water hickory Aphidomorpha community indicated that neither parthenogenesis nor endophagy sufficiently explain the occurrence of HAD in this system.  相似文献   

12.
    
Bemisia tabaci (Gennadius) MEAM1 (Hemiptera: Aleyrodidae) and Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), two important invasive species, are serious agricultural pests. In this study, a one‐step, single tube, duplex polymerase chain reaction (PCR) procedure was developed to allow rapid, specific, and sensitive identification of B. tabaci MEAM1 and F. occidentalis in predator guts. The system and conditions used for the duplex PCR were optimized. The species specificity of the duplex PCR determined by comparison against non‐targets that might interact with B. tabaci MEAM1 and F. occidentalis showed that oligonucleotide primers amplified nuclear gene target sequences present only in B. tabaci MEAM1 or F. occidentalis. The limits of detection were 9.53 ng μl?1 for B. tabaci MEAM1 and 8.94 ng μl?1 for F. occidentalis. Within a field cage study, in which predators Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) and Orius sauteri (Poppius) (Hemiptera: Anthocoridae) were allowed to feed on B. tabaci MEAM1 and F. occidentalis for 10 h, the B. tabaci MEAM1 DNA was detectable in 100% of H. axyridis and O. sauteri, and F. occidentalis DNA was detectable in 80% of H. axyridis and 90% of O. sauteri; this implicated that B. tabaci MEAM1 and F. occidentalis remains could be detected in native predator guts simultaneously. The accuracy and reliability of the assay suggested strongly that the duplex PCR optimized for B. tabaci MEAM1 and F. occidentalis is sensitive and specific for both invasive insects and is therefore useful in early diagnosis and monitoring of B. tabaci MEAM1 and F. occidentalis infections, and can be used to identify domestic predator species and food web relationships.  相似文献   

13.
    
The ability of a predator to discriminate against parasitized prey determines the extent of asymmetrical intraguild predation, which is often crucial for the outcome of biological control. Anagyrus nr. pseudococci (Girault) (Hymenoptera: Encyrtidae), a parasitoid of the citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae), suffers from intraguild predation by coccinellids occurring in the same habitat. The level of intraguild predation on A. nr. pseudococci by Nephus includens (Kirsch) (Coleoptera: Coccinellidae) at different immature stages has been investigated with and without simultaneous offer of extraguild prey. Larvae of A. nr. pseudococci appeared to face increased intraguild predation at early developmental stages, whereas mummification provided adequate protection against the predatory coccinellid. Different predation levels on unparasitized vs. parasitized hosts at various developmental stages in choice assays indicated that N. includens preferences might be determined not solely by palatability of the prey but also by its ability to protect itself.  相似文献   

14.
    
A monoclonal antibody (McAb), EGA-4A9, was developed to detect the semi-digested proteins of the English grain aphid, Sitobion avenae (Fabricius) (Hemiptera: Aphididae), in predatory ladybird beetles (species of the genera Adonia , Coccinella , Hippodamia , and Propylea ) using the gut homogenate of Adonia variegata (Goeze) (Coleoptera: Coccinellidae) adults which had fed on S. avenae as immunogen. The McAb was selected by screening hybridoma lines for antibodies that bound with the semi-digested aphid proteins in ladybirds. A double antibody sandwich enzyme-linked immuno-sorbent assay (ELISA) using ClonotypingTM System/HRP showed that it belonged to the IgG2a isotype. It did not cross-react with any of the 21 arthropod species tested besides the ladybird beetles fed on S. avenae with an indirect ELISA. It could still detect the semi-digested proteins in the gut of a ladybird adult, kept at 25 °C, that had ingested one aphid 6 days before. The extended antigen detection period and the high specificity of the antibody indicated that EGA-4A9 could be used to study interactions between English grain aphids and their ladybird predators in the field. Between 28 and 72% of coccinellids collected from the field were positive for English grain aphid protein by ELISA. The percentage of McAb-positive predatory ladybird beetles was positively correlated with the density of S. avenae in wheat fields.  相似文献   

15.
    
Nearly 5 000 aphid species damage crops, either by sucking plant sap or as disease‐transmitting vectors. Microsatellites are used for understanding molecular diversity and eco‐geographical relationships among aphid species. Expressed sequence tag (EST)‐microsatellite motifs were identified through an in silico approach using inbuilt simple sequence repeat mining tools in aphid EST dataset. Microsatellite mining revealed one in every five aphid genes as containing a repeat motif, and out of 9 290 EST microsatellites mined from Aphis gossypii Glover and Acyrthosiphon pisum (Harris) (both Hemiptera: Aphididae), 80% were of A and/or T (AT, ATA, AAT, AATA, and ATTT) motifs, and the rest contained G and/or C motifs. All microsatellite sequences were annotated using BLAST. Primers for EST microsatellites were designed using the Primer 3.0 tool. 106 primer pairs of both dinucleotide repeats (DNRs) and trinucleotide repeats (TNRs), representing open reading frames (ORFs) and untranslated regions (UTRs), were synthesized to amplify 15 aphid species belonging to the subfamily Aphidinae, collected from diverse hosts. Four hundred forty‐five polymorphic alleles were amplified. Fifty TNR and 23 DNR microsatellites amplified across the species studied. Polymorphism information content values of microsatellites ranged from 0.23 to 0.91, amplifying 2–16 alleles. Genetic similarity indices were estimated using the ‘NTSYS‐pc’ software package. Unweighted pair group with arithmetic mean and principal component analysis resolved taxonomic relationships of the aphid species studied. The new aphid microsatellites developed will provide valuable information to researchers to study Indian aphid species diversity and genetic relationships.  相似文献   

16.
    
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17.
    
We investigated the life history consequences of changes in diet between larval and adult life stages in the polyphagous lady beetle Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae). Beetles were reared on three larval diets: greenbug, Schizaphis graminum Rondani (Homoptera: Aphididae), eggs of the flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), and bee pollen. The reproductive performance of females was then evaluated on an adult diet of either greenbug or moth eggs. Moth eggs appeared to be the most suitable diet for larvae, yielding the largest adults, and pollen the least suitable, resulting in the smallest adults and greatly extended developmental time. Pollen‐reared beetles tended to have lower fecundity and fertility than those reared on animal protein, regardless of adult diet. Female fitness was generally increased by a change in diet upon emergence to the alternative source of animal protein, suggesting that dietary complementation occurred across life stages. Among females reared on greenbug, a change of diet to moth eggs reduced the period required for production of 12 clutches and increased egg fertility compared to continued feeding on greenbug. Among females reared on moth eggs, a change of diet to greenbug increased fecundity compared to continued feeding on moth eggs. Among females fed an adult diet of greenbug, those fed moth eggs as larvae had faster production of 12 clutches and higher fecundity. We discuss these novel results in the context of coccinellid life history and ecology and their potential implications for other insects that are predatory as both larvae and adults.  相似文献   

18.
    
Tobacco viruses transmitted by green peach aphids, Myzus persicae (Sulzer) (Hemiptera: Aphididae), cause severe disease in flue‐cured tobacco, Nicotiana tabacum L. (Solanaceae), in China and throughout the world. Field experiments were conducted in 2016 and 2017 in Longyan City, Fujian Province, China, to determine whether M. persicae and aphid‐transmitted virus diseases are affected by intercropping of oilseed rape, Brassica napus L. (Brassicaceae), in tobacco fields. The results showed that, compared with those in monocultured fields, the densities of M. persicae and winged aphids in intercropped fields significantly decreased in both 2016 and 2017. In particular, the appearance of winged aphids was delayed by ca. 7 days. Moreover, the densities of Aphidius gifuensis Ashmead (Hymenoptera: Aphidiidae), a parasitoid of the aphid, significantly increased in 2016 and 2017. Accordingly, the incidence rates of aphid‐transmitted virus diseases (those caused by the cucumber mosaic virus, potato virus Y, and tobacco etch virus) significantly decreased in the intercropped fields in 2016 and 2017. Tobacco yields and monetary value significantly increased in 2016 (by 10–25 and 14–29%, respectively) and 2017 (by 17–22 and 22–34%, respectively). Consequently, our results suggest that intercropping oilseed rape in tobacco fields is a good approach to regulating and controlling aphids and tobacco mosaic viruses, for example potyvirus, and this intercropping can help control aphid‐transmitted virus diseases in tobacco.  相似文献   

19.
    
Carotenoids are used for many functions by animals, including combining with other pigments to produce aposematic and cryptic coloration. Carotenoids in combination with blue pigments are responsible for green coloration in many caterpillars, and thus carotenoid sequestration may reduce their contrast against a green foliage background. We tested the hypothesis that carotenoid sequestration reduces contrast and enhances survival by rearing Trichoplusia ni Hübner (Lepidoptera: Noctuidae) on Brassica oleracea L. var. Acephala (Brassicaceae) leaves and exposing them to predators. We found that carotenoids derived from the host plant are partially excreted, along with chlorophyll, but also sequestered in hemolymph. Larvae that were given plants that provided carotenoids showed less contrast against their host plants within 1 day compared to larvae that were not provided with carotenoids. Last, both short‐term field observations and laboratory trials of larvae caged with predatory Podisus maculiventris Say (Hemiptera: Pentatomidae) nymphs showed that survival of carotenoid‐sequestering larvae was higher compared to larvae that did not sequester. These results suggest that carotenoid sequestration may be an important adaptive strategy that reduces susceptibility to natural enemies that hunt by sight. Further research that examines the mechanisms by which carotenoids are absorbed and modified will lend insights into the evolution of carotenoids functioning as passive defensive compounds.  相似文献   

20.
    
Feeding behavior of Melanaphis sacchari Zehntner (Hemiptera: Aphididae) was studied on sugarcane, Saccharum spp. (Poaceae), cultivars HoCP 91‐555 (resistant), LCP 85‐384 (moderately resistant), and L 97‐128 (susceptible) using the electrical penetration graph (EPG) technique. Constitutive concentrations of total phenolics and available carbohydrates, water potential at the whole‐leaf tissue level, and free amino acids (FAAs) in phloem sap extracts, and in honeydew produced by aphids fed on L 97‐128 and HoCP 91‐555 were determined. Cultivar did not influence time for M. sacchari to access phloem sieve elements. Total time in sieve elements was ca. two‐fold greater on L 97‐128 than on HoCP 91‐555, whereas it did not differ from LCP 85‐384 in either cultivar. The mean duration of individual events associated with phloem sap ingestion was ca. 50% shorter on both HoCP 91‐555 and LCP 85‐384 than on L 97‐128. Although cultivar effects were not detected for levels of total phenolics, available carbohydrates, and water potential, two free essential amino acids, histidine and arginine, were absent from phloem sap in HoCP 91‐555. Two free essential amino acids, leucine and isoleucine, and two free non‐essential amino acids, tyrosine and proline, were absent from honeydew of aphids fed on HoCP 91‐555. These results suggest that despite apparent biosynthesis of some FAAs, the absence of important FAAs in the phloem sap of HoCP 91‐555 and the inability of M. sacchari and its endosymbionts (e.g., Buchnera) to derive specific free essential and non‐essential amino acids from other ingested molecules, possibly along with other unidentified factors, underlie the pest's decreased phloem sap ingestion and consequently reduced growth potential on HoCP 91‐555.  相似文献   

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