The role of natural enemy guilds in Aphis glycines suppression

Generalist natural enemy guilds are increasingly recognized as important sources of mortality for invasive agricultural pests. However, the net contribution of different species to pest suppression is conditioned by their biology and interspecific interactions. The soybean aphid, Aphis glycines (Hemiptera: Aphididae), is widely attacked by generalist predators, but the relative impacts of different natural enemy guilds remains poorly understood. Moreover, low levels of A. glycines parasitism suggest that resident parasitoids may be limited through intraguild predation. During 2004 and 2005, we conducted field experiments to test the impact of different guilds of natural enemies on A. glycines. We contrasted aphid abundance on field cages with ambient levels of small predators (primarily Orius insidiosus) and parasitoids (primarily Braconidae), sham cages and open controls exposed to large predators (primarily coccinellids), and cages excluding all natural enemies. We observed strong aphid suppression (86- to 36-fold reduction) in treatments exposed to coccinellids, but only minor reduction due to small predators and parasitoids, with aphids reaching rapidly economic injury levels when coccinellids were excluded. Three species of resident parasitoids were found attacking A. glycines at very low levels (<1% parasitism), with no evidence that intraguild predation by coccinellids attenuated parasitoid impacts. At the plant level, coccinellid impacts resulted in a trophic cascade that restored soybean biomass and yield, whereas small natural enemies provided only minor protection against yield loss. Our results indicate that within the assemblage of A. glycines natural enemies in Michigan, coccinellids are critical to maintain aphids below economic injury levels.     

Parasitism of the soybean aphid, Aphis glycines by Binodoxys communis: the role of aphid defensive behaviour and parasitoid reproductive performance

The Asian parasitoid, Binodoxys communis (Gahan) (Hymenoptera: Braconidae), is a candidate for release against the exotic soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), in North America. In this study, we examined preferences by B. communis for the different developmental stages of A. glycines and investigated consequences of these preferences for parasitoid fitness. We also determined to what extent aphid defensive behaviours mediate such preferences. We found that B. communis readily attacks and successfully develops in the different A. glycines developmental stages. Binodoxys communis development time gradually increased with aphid developmental stage, and wasps took longest to develop in alates. An average (+/-SE) of 54.01+/-0.08% of parasitized A. glycines alatoid nymphs transformed into winged adult aphids prior to mummification. No-choice assays showed a higher proportion of successful attacks for immature apterous A. glycines nymphs compared to adults and alatoid nymphs. Also, choice trials indicated avoidance and lower attack and oviposition of adults and alatoid nymphs. The different aphid stages exhibited a range of defensive behaviours, including body raising, kicking and body rotation. These defenses were employed most effectively by larger aphids. We discuss implications for the potential establishment, spread and biological control efficacy of A. glycines by B. communis in the event that it is released in North America.     

Hymenopteran parasitoids and dipteran predators of the invasive aphid Diuraphis noxia after enemy introductions: Temporal variation and implication for future aphid invasions

Shifts in prevalence and abundance of hymenopteran parasitoids and dipteran predators, Diuraphis noxia, and other aphids were measured in the west-central Great Plains of North America, April–September, in 2001 and 2002, corresponding to over a decade after first detection of D. noxia and first release of D. noxia enemies. Significant temporal shifts in enemy species prevalence and diversity were detected in this study and more broadly during an 11 year time span. At any given time, some species were relatively common. One parasitoid had been predominant throughout (Aphelinus albipodus), two had shifted in dominance (Lysiphlebus testaceipes and Diaeretiella rapae), three parasitoids had been detected infrequently (Aphidius avenaphis, Aphidius matricariae, and Aphelinus asychis), one parasitoid was detected in the 1990s but not during 2001 and 2002 (Aphelinus varipes), two predatory flies occurred at occasional significant levels (Leucopis gaimarii and Eupeodes volucris), and two parasitoids may have been minor members of the fauna (Aphidius ervi and Praon yakimanum). Aphid populations detected were usually very low or not detected, precluding estimation of percent parasitism. The best evidence of suppression was observations of parasitoids in the rare case of D. noxia exceeding economic thresholds, which complemented past studies using high aphid densities. The D. noxia enemies detected were primarily endemic or long-time residents derived from previous introductions. This enemy community may provide flexibility in responding to a future aphid invasion, allowing more strategic use of biological control and other pest management approaches.     

烟蚜茧蜂随寄主有翅桃蚜迁飞而被携带扩散的模拟实验

蚜虫寄生蜂的广泛分布可能与有翅蚜的迁飞有关。为了证明这一假说, 本研究利用微小昆虫飞行磨系统, 分数十批(≤16头/批)对被烟蚜茧蜂Aphidius gifuensis Ashmead单头寄生后的有翅桃蚜Myzus persicae (Sulzer)进行模拟飞行并系统观察了飞行后有翅桃蚜的单头定殖情况。对实验观察数据按飞行时间和飞行距离进行归类, 采用单因素方差分析方法分析飞行时间和飞行距离对有翅桃蚜定殖后的存活和生殖力、烟蚜茧蜂发育等变量的影响; 采用多项式回归分析对所有变量和归类的数据进行统计和分析。结果表明: 成功飞行并定殖的有翅桃蚜有378头, 其中239头有翅桃蚜定殖后形成僵蚜。形成僵蚜的有翅桃蚜在飞行实验时平均飞行时间和飞行距离分别为2.63 h和2.16 km, 定殖后平均存活了6.11 d, 定殖第6天和第14天平均产若蚜累计数量分别为8.5头和162头。形成僵蚜和未形成僵蚜的有翅蚜的模拟飞行数据和定殖观察数据无显著差异。形成僵蚜的239头有翅桃蚜中, 最终成功育出烟蚜茧蜂205头, 僵蚜出蜂率为85.8%。雌雄性比为1∶5.2。结论认为, 专性寄生蚜虫的烟蚜茧蜂可以利用有翅蚜的迁飞而被携带扩散传播, 有翅蚜迁飞在蚜虫寄生蜂扩散中具有重要作用。     

Larvicidal activity of lectins onLucilia cuprina: mechanism of action

Foraging behaviour and host-instar preference of young and old females of the solitary aphid parasitoid,Lysiphlebus cardui Marshall (Hymenoptera: Aphidiidae), were studied in the laboratory. The analysis of interactions between parasitoids and different stages ofAphis fabae cirsiiacanthoidis Scop. (Homoptera: Aphididae) revealed that encounter rates between aphids and parasitoid females and defence reactions of the aphids influenced the degree to which a particular aphid age class is parasitized. Encounter rates between hosts and parasitoid females depended on the foraging pattern of the parasitoid, which varied with age. In mixed aphid colonies patch residence time increased with parasitoid age. Furthermore, younger parasitoids (≦1 day old) laid more eggs into second and third instars, while older parasitoids (≧4 days old) did not show distinct host instar preferences. It is suggested that the oviposition behaviour ofL. cardui is influenced by the physiological state, i.e. the age of the wasp.     

Predator and parasitoid attacking ant-attended aphids: effects of predator presence and attending ant species on emerging parasitoid numbers

Interaction between a predator and a parasitoid attacking ant-attended aphids was examined in a system on photinia plants, consisting of the aphid Aphis spiraecola, the two ants Lasius japonicus and Pristomyrmex pungens, the predatory ladybird beetle Scymnus posticalis, and the parasitoid wasp Lysiphlebus japonicus. The ladybird larvae are densely covered with waxy secretion and are never attacked by attending ants. The parasitoid females are often attacked by ants, but successfully oviposit by avoiding ants. The two ants differ in aggressiveness towards aphid enemies. Impacts of the predator larvae and attending ant species on the number of parasitoid adults emerging from mummies per aphid colony were assessed by manipulating the presence of the predator in introduced aphid colonies attended by either ant. The experiment showed a significant negative impact of the predator on emerging parasitoid numbers. This is due to consumption of healthy aphids by the predator and its predation on parasitized aphids containing the parasitoid larvae (intraguild predation). Additionally, attending ant species significantly affected emerging parasitoid numbers, with more parasitoids in P. pungens-attended colonies. This results from the lower extent of interference with parasitoid oviposition by the less aggressive P. pungens. Furthermore, the predator reduced emerging parasitoid numbers more when P. pungens attended aphids. This may be ascribed to larger numbers of the predator and the resulting higher levels of predation on unparasitized and parasitized aphids in P. pungens-attended colonies. In conclusion, a negative effect of the predator on the parasitoid occurs in ant-attended aphid colonies, and the intensity of the interaction is affected by ant species.     

Transient host paralysis as a means of reducing self-superparasitism in koinobiont endoparasitoids

The term ‘idiobiont’ refers to those parasitoid species that permanently paralyse their hosts during parasitism, causing the cessation of host growth and development. This is in contrast to koinobiont parasitoids, which allow their hosts to continue developing after being parasitized. While no koinobiont species induce permanent paralysis in their hosts, a minority of koinobionts induce a temporary paralysis that does not interfere with overall host growth and development. We characterized transient paralysis induction in two koinobiont aphid parasitoids in the genus Binodoxys (Hymenoptera: Aphidiinae). Both Binodoxys species induced transient paralysis in Aphis glycines, with paralysis time ranging between 4.5 and 8 min (depending upon parasitoid species and host instar). In a separate experiment, B. communis was capable of inducing transient paralysis in nine aphid species. We addressed two hypotheses potentially explaining the adaptive value of temporary host paralysis in experiments using A. nerii, which is readily accepted but engages in strong defensive behaviour. The first hypothesis is that paralysis increases oviposition success by interfering with host defences and the second is that it aids in the avoidance of self-superparasitism. Paralysed aphids were more likely to be rejected by B. communis than were aphids that had never been stung or that had recovered from paralysis. This result supports the avoidance-of-self-superparasitism hypothesis and is inconsistent with the hypothesis that transient paralysis increases oviposition success of B. communis.     

Aphelinus albipodus(Hymenoptera: Aphelinidae) andDiaeretiella rapae(Hymenoptera: Braconidae) Parasitism onDiuraphis noxia(Homoptera: Aphididae) Infesting Barley Plants Differing in Plant Resistance to Aphids

Russian wheat aphid,Diuraphis noxia(Mordvilko), as a pest of small grains, has prompted research into biological control and host plant resistance. In the presence of Russian wheat aphid, leaves of a susceptible barley (Morex) are curled and chlorotic and sustain large densities of this aphid, while leaves of a resistant barley (STARS-9301B) remain flat and green and sustain fewer aphids. Might parasitism of Russian wheat aphid byAphelinus albipodusHayat & Fatima andDiaeretiella rapaeMcIntosh be affected differently by these plant types? When presented the plants separately and based on parasitism rate relative to aphid density, the largerD. rapaewas more effective in parasitizing relatively high densities of aphids within curled leaves of Morex than relatively low densities of aphids on uncurled leaves of STARS-9301B. Parasitism byA. albipodusdid not significantly differ among the plants. When given a choice of plants, approximately equal rates of parasitism occurred on the two plant lines for both parasitoid species, and parasitism byD. rapaewas greater thanA. albipodus.These data indicate that using parasitoid size as an indicator of success in a physically restricted environment may be misleading, when considered in a plant environment responsive in several manners to aphids (chlorosis, curling, and ability to sustain Russian wheat aphid). We expect that use of resistant barley will result in decreased parasitoid abundance as aphid densities decrease. However, parasitism rates are expected to be approximately equal on resistant and susceptible barley. In this system, plant resistance and biocontrol are compatible management strategies.     

Oviposition avoidance of parasitized aphid colonies by the syrphid predator Episyrphus balteatus mediated by different cues

Oviposition decisions made by members of a guild of natural enemies can have evolved to avoid intraguild predation, potentially avoiding the disruption of the extraguild prey control. We have studied the oviposition preference of the aphidophagous predator Episyrphus balteatus De Geer (Diptera: Syrphidae) within colonies of Myzus persicae Sulzer (Hemiptera: Aphididae) in the presence of two developmental stages of the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Aphidiidae). Results from a greenhouse choice experiment showed that E. balteatus females lay significantly fewer eggs in colonies with mummified aphids than in unparasitized colonies. Colonies of parasitized, but not yet mummified did not contain significantly fewer eggs than colonies with unparasitized aphids. In three no-choice experiments, we assessed stimuli coming from aphid honeydew, from the aphids themselves and also from extracts of the aphid bodies, and all of these stimuli mediate the discrimination of mummified aphids from healthy aphids. To a lesser extent these stimuli also contribute to the discrimination against aphids that are parasitized but not yet mummified. These results suggest that the effects of these two species could be complementary for the control of M. persicae, since the species that acts as an intraguild predator, E. balteatus, avoids ovipositing on aphid colonies parasitized by the intraguild prey, A. colemani.     

The performance of an aphid parasitoid is negatively affected by the presence of a circulative plant virus

Plant viruses and aphids can interact via contest competition for plant resources and induce changes in plant physiology, which can have effects on a third trophic level. The aim of this study was to determine how the interactions between a circulative plant virus and its aphid vector may affect the performance of an endoparasitoid and how parasitism may affect the efficiency of virus transmission by its aphid vector. The timing when parasitized aphids were transferred to virus-infected lettuce leaves was critical for the performance of A. ervi. Higher parasitoid larvae mortality, longer developmental times and lower percentages of mummification were detected on viruliferous/parasitized aphid nymphs when the time lag between parasitism and exposure to the virus was less than 24 h. No significant differences were detected in virus transmission rate between parasitized and non-parasitized M. euphorbiae aphids.     

Multifaceted determinants of host specificity in an aphid parasitoid

The host specificity of insect parasitoids and herbivores is thought to be shaped by a suite of traits that mediate host acceptance and host suitability. We conducted laboratory experiments to identify mechanisms shaping the host specificity of the aphid parasitoid Binodoxys communis. Twenty species of aphids were exposed to B. communis females in microcosms, and detailed observations and rearing studies of 15 of these species were done to determine whether patterns of host use resulted from variation in factors such as host acceptance or variation in host suitability. Six species of aphids exposed to B. communis showed no signs of parasitism. Four of these species were not recognized as hosts and two effectively defended themselves from attack by B. communis. Other aphid species into which parasitoids laid eggs had low suitability as hosts. Parasitoid mortality occurred in the egg or early larval stages for some of these hosts but for others it occurred in late larval stages. Two hypotheses explaining low suitability were investigated in separate experiments: the presence of endosymbiotic bacteria conferring resistance to parasitoids, and aphids feeding on toxic plants. An association between resistance and endosymbiont infection was found in one species (Aphis craccivora), and evidence for the toxic plant hypothesis was found for the milkweed aphids Aphis asclepiadis and Aphis nerii. This research highlights the multifaceted nature of factors determining host specificity in parasitoids.     

Host nutritional status mediates degree of parasitoid virulence

Parasitic organisms rely on the resources of their hosts to obtain nutrients essential for growth and reproduction. Insect parasitoids constitute an extreme condition since they develop in a single host from which they typically consume all available resources. As a result, the host is killed following parasitism. However, a few intriguing cases of host survival have been reported wherein hosts resume foraging and may even reproduce following parasitoid emergence. Yet, the ultimate and proximate mechanisms responsible for host recovery remain unresolved. We tested the impact of host nutrition on host fate and parasitoid fitness, using the association between Dinocampus coccinellae and the spotted lady beetle Coleomegilla maculata. Under laboratory conditions, we fed parasitized ladybirds on different aphid diets, with or without pollen. In the field, we followed the fate of parasitized ladybirds during seasonal variations in pollen and aphid abundance. We found that ladybirds fed on aphids or a combination of aphids and pollen recovered more frequently from parasitism (from 65 to 81%) than those eating only pollen (48%). Field data suggest that the fate of parasitized ladybirds is also related to food availability. On the other hand, when hosts fed on a combination of aphids and pollen, consequences for parasitoid fitness were often ‘all‐or‐nothing’: parasitoid emergence rate was the lowest of all host nutrition regimes (～50%), but parasitoids that did emerge were larger than individuals emerging from other host nutrition regimes. Laboratory and field results concur to show that host nutritional status during parasitoid development significantly influences both host fate and parasitoid fitness.     

Interference between parasitoids [Hym.: Aphidiidae] and fungi [Entomophthorales] attacking cereal aphids

In field populations of cereal aphids parasitism levels declined through the season as fungal infection increased. In laboratory trials the fungusErynia neoaphidis Remaudiere & Hennebert took 3 to 4 days to kill the rose-grain aphid,Metopolophium dirhodum (Walker), whereas the parasitoidAphidius rhopalosiphi De Stefani-Perez took 8 to 9 days at 20°C. When aphids were infected by the fungus less than 4 days after being parasitized the parasitoids were prevented from completing their development. Conversely, when infection occurred more than 4 days after parasitization development of the fungus was significantly impaired. There was no histological evidence that the fungus invaded the tissues of the parasitoid when both attacked the same aphid. Interference between parasitoids and fungal pathogens must be taken into account when estimating the impact of these mortality agents on pest populations.     

Density-dependent parasitism of cowpea aphid,Aphis craccivora by Lysiphlebus fabarum,Binodoxys acalephae,and Aphidius matricariae (Hymenoptera: Braconidae: Aphidiinae)

Biological control, as a major component of pest management strategies, uses natural biological agents to reduce pest populations. Studying the interaction among Aphis craccivora and its parasitoids including, Lysiphlebus fabarum, Binodoxys acalephae, and Aphidius matricariae in 2016 and 2017 in Tehran Parke-Shahr, showed positive, significant correlations in all cases between the densities of three parasitoid species and that of aphid nymphs and adults. The density of the parasitoids increased by increasing the density of the aphids. The parasitoids showed aggregative behavior in response to different densities of the host. There was a positive density-dependent correlation between the density of A. craccivora and rate of parasitism. Parasitism rates of nymphs and adult aphids by L. fabarum, B. acalephae, and A. matricariae increased or decreased along with decline or increase in the population of the aphid host. In 2016 spring, the highest rates of parasitism on aphid nymphs by L. fabarum, B. acalephae, and A. matricariae were 46.82, 23.09, and 17.16%, respectively. In 2017 spring, the highest rates of parasitism on aphid nymphs by L. fabarum, B. acalephae, and A. matricariae were 48.97, 21.77, and 15.06%, respectively. So, given the accordance between changes in aphid population and that of parasitoids, and parasitoids’ efficacy in Tehran’s polluted air, they can be used as biological agents in the management of A. craccivora population.     

Wing development in parasitized male and female Sitobion fragariae

Abstract.Different stages of presumptive winged morphs (males, gynoparae and alate virginoparae) of the blackberry‐cereal aphid, Sitobion fragariae , were exposed to attack by Aphidius ervi . Even though the mechanism influencing wing development in the three aphid morphs differs, the effects of parasitism were similar. Alatiform structures were completely inhibited in all three morphs when the initial attack took place in their first or early second stadium. The disruption of wing development also resulted in apterous/alate‐intermediate forms when aphids were attacked from first (males and gynoparae) or early second (alate virginoparae) up to the fourth larval stadium. The fact that wing development was still disrupted when aphids with well developed wingbuds were parasitized indicates that the early stages of parasitization were influential. Thus, the morphogenetic effects may be exerted by the parasitoid egg or calyx fluid.     

Morphological observations on the preimaginal stages ofAphelinus varipes (Hym., Aphelinidae) and the effects of this parasitoid on the aphidRhopalosiphum padi (Hom., Aphididae)

Three instar larvae could be observed forAphelinus varipes. In the second and third instars, the colon which forms the largest part of the hindgut was composed of secretory cells. There was a reduction in the size and number of embryos produced by parasitized aphids. Fat cells of parasitized aphids also degenerated sooner than those of unparasitized aphids. The number of mycetocytes remained higher in parasitizedRhopalosiphum padi than in non-parasitized aphids. During the last instar ofA. varipes the host aphid developed into a mummy in which black pigments were incorporated into the exocuticle and the integument of the aphid became sclerotized.     

Parasitoids associated with the common pistachio psylla, Agonoscena pistaciae, in Iran

The parasitoids associated with the common pistachio psylla, Agonoscena pistaciae Burckhardt and Lauterer, were investigated at three pistachio plantations in Rafsanjan, Iran. Of the 6504 wasps emerging from mummified psyllids, 46% were the primary parasitoid Psyllaephagus pistaciae Ferrière, and the remaining 54% represented six species of hymenopterous hyperparasitoids, including Chartocerus kurdjumovi (Nikol’skaja), Marietta picta (André), Pachyneuron aphidis (Bouché), Pachyneuron muscarum (Linnaeus), Psyllaphycus diaphorinae (Hayat), and Syrphophagus aphidivorus (Mayr). Lysiphlebus fabarum Marshall, the parasitoid of Aphis gossypii Glover and Aphis craccivora Koch present on weeds, was found to be an alternative host for three major hyperparasitoids of A. pistaciae. The most abundant hyperparasitoid was S. aphidivorus, appearing during the growing season in all trial locations on psyllids and aphids in pistachio orchards. The weed-infesting aphids, along with their primary parasitoid, can act as a reservoir of A. pistaciae secondary parasitoids. Therefore, parasitized aphids allow populations of secondary parasitoids to increase and consequently to apply higher pressure on P. pistaciae. We detected that two primary parasitoid species, including P. pistaciae and L. fabarum, attacking different species of hosts interact indirectly through shared secondary parasitism. It is suggested that the community structure of A. pistaciae may be influenced by apparent competition, although more work is needed to provide firm evidence.     

Xylem ingestion by winged aphids

When aphids and their host plant are incorporated in a DC electrical circuit, phloem and xylem ingestion register as separate waveforms of the electrical penetration graph (EPG) signal. Aphids are primarily phloem feeders; xylem ingestion is seldom reported but can be induced experimentally by fasting the insects in desiccating conditions. In experiments with the black bean aphid, Aphis fabae Scop., young winged (alate) and unwinged (apterous) virginoparous adults were collected from their natal host plants (broad bean, Vicia faba L.) and allowed 3-h continuous EPG-recorded access to V. faba seedlings. Several aphids (47% of both morphs) showed ingestion from phloem sieve elements. Alate aphids also showed frequent xylem ingestion (60% of individuals), but no apterous aphids exhibited this activity. The EPG technique involves attachment of a fine gold wire electrode to each insect, a process that may affect normal behaviour at the plant surface. However, when the technique was modified to monitor the stylet activities of freely-settled aphids, high levels of xylem ingestion by alates were also recorded. The results suggest that the developmental physiology of winged aphids somehow predisposes them to xylem ingestion, possibly as a result of dehydration during the teneral period. Alate aphids may reduce their weight by fasting before take-off, giving aerodynamic benefits, but making rehydration, via xylem uptake, a priority following plant contact.     

Combined effects of host-plant resistance and intraguild predation on the soybean aphid parasitoid Binodoxys communis in the field

Soybean varieties that exhibit resistance to the soybean aphid Aphis glycines have been developed for use in North America. In principle, host-plant resistance to soybean aphid can influence the interactions between the soybean aphid and its natural enemies. Resistance could change the quality of soybean aphids as a food source, the availability of soybean aphids, or resistance traits could directly affect aphid predators and parasitoids. Here, we focus on the effect of soybean aphid resistance on the interactions between soybean aphids, the parasitoid Binodoxys communis (Hymenoptera: Braconidae), and predators of these two species. We determined whether host-plant resistance affected within-season persistence of B. communis by releasing parasitoids into resistant and susceptible soybean plots. We observed higher B. communis densities in susceptible soybean plots than in resistant plots. There were also higher overall levels of intraguild predation of B. communis in susceptible plots, although the per-capita risk of intraguild predation of B. communis was affected neither by plant genotype nor by aphid density. We discuss these effects and whether they were caused by direct effects of the resistant plants on B. communis or indirect effects through soybean aphid or predators.     

Flying with a 'death sentence' on board: electrophoretic detection of braconid parasitoid larvae in migrating winged grain aphids, Sitobion avenae (F.)

Polyacrylamide gel electrophoresis of enzymes (carboxylesterases) was used for the first time to monitor rates of parasitism in airborne alate (winged) grain aphid, Sitobion avenae (F.) population samples collected by suction trapping in Hertfordshire, UK. Using previously described electrophoretic 'keys', the species of hymenopterous parasitoids present in individual aphids were identified and found to be Aphidius ervi (Haliday) and/or Aphidius rhopalosiphi (De Stephani Perez) (Braconidae). Entomophthoralean fungal infection was also detected using this approach. Aphidiid wasp parasitism was detected from early June to mid-August and fungal infection from late June to late July. The results are discussed in relation to parasitoid population structure and dynamics, especially (i) the fact that winged aphids passively transport the early stages of their braconid parasitoids and fungal pathogens, potentially to newly-founded colonies, which may directly impact on the dual aphid-parasitoid populations genetics; and (ii) the approach used to collect and assay parasitised and fungal infected aphids involving both suction trapping and electrophoretic testing may have potential in assessing the level and efficacy of these biological control agents in integrated pest management (IPM) schemes to combat cereal aphid outbreaks.