Aphid Colonies Research Articles

Feeding and egg distribution studies of Heringia calcarata (Diptera: Syrphidae), a specialized predator of woolly apple aphid (Homoptera: Eriosomatidae) in Virginia apple orchards.

Predation by the aphidophagous syrphid fly Heringia calcarata (Loew) on woolly apple aphid, Eriosoma lanigerum (Hausmann), was studied in the laboratory and in Virginia apple orchards. Feeding studies compared the prey suitability of three temporally sympatric aphid pests of apple: spirea aphid, Aphis spiraecola Patch; rosy apple aphid, Dysaphis plantaginea (Passerini); and woolly apple aphid. Significantly more H. calcarata larvae survived and completed development on a pure diet of woolly apple aphid than on rosy apple aphid, and none survived on spirea aphid. Final larval weights were significantly greater, and the larval developmental period was significantly shorter on woolly apple aphid than on rosy apple aphid, but neither the duration of pupal development nor adult weight differed between diets. H. calcarata larvae consumed an average of 105 woolly apple aphids during their development. Naïve, neonate larvae given access to all possible pair combinations of woolly apple aphid, rosy apple aphid, and spirea aphid consumed significantly more woolly apple aphids in all pairings that included woolly apple aphid. When given a choice of rosy apple aphid and spirea aphid, significantly more rosy apple aphids were consumed. Weekly counts of syrphid eggs found in woolly apple aphid, rosy apple aphid, and spirea aphid colonies collected from apple trees showed that two generalist hover fly predators, Eupeodes americanus (Wiedemann) and Syrphus rectus Osten Sacken, were present in colonies of all three aphid species and that E. americanus was the most abundant syrphid predator in A. spiraecola and D. plantaginea colonies. H. calcarata eggs were found only in woolly apple aphid colonies and were more abundant there than E. americanus and S. rectus. These data suggest that H. calcarata is a specialized predator of woolly apple aphid in the apple ecosystem in Virginia.

Tritrophic interactions in the context of climate change: a model of grasses, cereal Aphids and their parasitoids

AbstractBiologists have been challenged to envisage the likely consequences of increases in atmospheric carbon dioxide concentrations, and the suite of accompanying environmental changes (e.g. rising temperature, changing rainfall patterns, etc.) on our biotic systems. Research to date on plant responses has been extensive, but work on herbivore responses has been less complete, and work on higher trophic levels nearly nonexistent. One group of herbivores that has been reasonably well studied is aphids, and at least for this group, researchers have even begun to investigate responses at higher trophic levels, to include parasitoids. In this paper, we develop a mechanistic mathematical model of the general interaction between grasses, cereal aphids and their parasitoids. We used this model to investigate the interacting effects of rising CO2and temperature. The model suggests that, while parasitoids do have an impact on the aphid colony population dynamics, they do not fundamentally alter the aphid response to climate change. The model predicts that for both aphids and their parasitoids, the population responses to combined effects of elevated CO2and temperature will be more similar to current ambient conditions than we might expect from the individual effects of CO2or temperature increases. This interaction has important consequences for the interpretation of results from experiments that study only the effect of rising CO2.

Reduction in transport in wheat (Triticum aestivum) is caused by sustained phloem feeding by the Russian wheat aphid (Diuraphis noxia)

The Russian wheat aphid ( Diuraphis noxia ) feeds preferentially from the phloem of longitudinal veins of non-resistant wheat leaves. The xenobiotic, 5,6-CFDA was applied to exposed leaf blade mesophyll cells in control and aphid-infested plants. In control plants, the fluorophore moved approximately 5–6cm from the point of application of 5,6-CFDA within 3h of application. The fluorochrome was transported in the sieve tube companion cell complex, including those in the numerous interconnecting transverse veins. Leaf blades on which the Russian wheat aphid had been feeding demonstrated a marked decrease in 5,6-CF transport. Aphids feeding on the leaves formed local sinks and redirected the fluorophore (and presumably associated assimilate) to the aphids’ gut, with little longitudinal translocation of 5,6-CF below inserted stylets or aphid feeding areas. Aniline blue staining revealed massive deposits of wound and reaction callose caused by the aphids, with callose associated with the sieve plates, pore-plasmodesma between the companion cells and their associated sieve tubes, as well as with plasmodesmal aggregates in parenchymatous elements within the vascular bundles. Leaves that had been colonised by aphids but from which the aphids were removed, showed extensive wound callose deposits, which persisted for up to 48h after removal of aphid colonies, suggesting that the damage caused by aphid feeding is a long-term, non-transient event in non-resistant plants.

Development and consumption capacity of Chrysoperla externa (Hagen) (Neuroptera, Chrysopidae) fed with Cinara spp. (Hemiptera, Aphididae) under three temperatures

The giant conifer aphids Cinara pinivora (Wilson, 1919) and Cinara atlantica (Wilson, 1919) (Hemiptera: Aphididae) are pests on Pinus spp. (Pinaceae) in the South and Southeast regions of Brazil. Larvae of Chrysoperla externa (Hagen, 1861) (Neuroptera, Chrysopidae) were observed feeding voraciously on these aphid colonies. In order to evaluate their potential as biological control agents, some biological parameters and their consumption capacity were studied in laboratory. Ten larvae were isolated in plastic vials and fed with aphids of small size (nymphs of 1st and 2nd instars) and 10 with aphids of medium size (nymphs of 3rd and 4th instars), maintained at 15ºC, 20ºC and 25ºC, under 12:12 h photoperiod and 70 ± 10% RH, and observed daily. The egg incubation period was nine days at 20ºC and four days at 25ºC. The mean larval development period for C. externa was 59.5 days; 22.3 days and 10.9 days, respectively at 15ºC, 20ºC and 25ºC. The pupal stage last 23.2 at 20ºC and 11.1 days at 25ºC. Unfortunately, data of egg and pupal development at 15ºC are not available because the rearing chamber overheated. The mortality rate from egg to adult was 46.2% 46.6% and 20.2% at 15ºC, 20ºC and 25ºC, respectively. The average aphid consumption of each C. externa larva to complete its development was 499.1; 341.7 and 215.1 small aphids, and 126.4; 105.6 and 67.0 medium aphids, at 15ºC, 20ºC and 25ºC, respectively. About 80% of the total food consumption was by the 3rd instar larvae. Although the development was faster and viability higher at 25ºC than at the other two temperatures, the consumption was the highest at 15ºC because the larval period was much longer. Therefore, the larvae of C. externa can be regarded as potential biological control agents of Cinara spp. throughout the year and even in cool areas of Southern Brazil during some periods o the year.

Adaptations of Coccinella magnifica, a myrmecophilous coccinellid to aggression by wood ants (Formica rufa group). II. Larval behaviour, and ladybird oviposition location1

Like adults, larvae of the myrmecophilous ladybird Coccinella magnifica are rarely attacked by Formica rufa ants on foraging trails, but more often attacked on ant-tended aphid colonies. Larvae of the non-myrmecophile Coccinella septempunctata, to which C. magnifica was compared, were more readily attacked by ants in both situations. To avoid or counter ant aggression when foraging for aphids, C. magnifica larvae exhibit three main tactics: they may feed on un- or non-tended aphids; when feeding on tended colonies they often carry prey away, minimising time spent there; and if attacked, they use limited chemical defence. No novel behaviours were found in C. magnifica larvae, not occurring to some extent in C. septempunctata. Coccinella magnifica eggs were laid distant to ant-tended aphids, although closer to un- or non-tended aphids.

Role of aphid predator guild in controlling spirea aphid populations on apple in West Virginia, USA

Abstract Spirea aphid populations and their predators were studied on apple to identify predators of importance in controlling aphid populations. Methods included random and non-random sampling from apple orchards in West Virginia, USA, sentinel aphid colonies, laboratory feeding studies, and predator exclusion studies. Aphidoletes aphidimyza (Diptera: Cecidomyiidae), chrysopids (Neuroptera: Chrysopidae), Harmonia axyridis (Coleoptera: Coccinellidae), and Orius insidiosus (Hemiptera: Anthocoridae) were the most abundant predators associated with spirea aphid colonies on apple. Parasitoids were all but absent in the study. Abundance of all predators was density dependent with greater responses to aphid populations at the orchard scale than to tree or individual colony scales. A. aphidimyza, O. insidiosus, chrysopids, and syrphids (Diptera) had the greatest degree of density dependence on aphid populations, and spiders showed inverse density dependence. Exclusion of predators with both cages and insecticides produced significantly higher aphid populations. Because of high abundance, good synchrony with aphid populations, and high impact per individual, H. axyridis adults were the most important spirea aphid predator on apple.

Logistic model for soldier production in aphids

The number of aphid soldiers in a colony is positively correlated with colony size. This positive correlation has been repeatedly confirmed for the bamboo aphid Pseudoregma bambucicola. To explain this, we present a simple model assuming logistic growth of the aphid colony. The model predicts that a first soldier is more readily produced in large colonies than in small colonies. This is because the productivity of each reproductive decreases as the colony size increases, and also because the efficiency of defense increases as the number of reproductives defended by the soldier increases. The latter effect disappears when the number of reproductives exceeds N p, the critical number of reproductives that a predator could damage. This argument holds for a second, a third, and an ith soldier in general. Although we assume logistic growth of the aphid colony, the model is applicable to any form of colony growth with minor changes of some premises.

Consumo de Uroleucon ambrosiae (Thomas, 1878) (Hemiptera: Aphididae) por larvas de Chrysoperla externa (Hagen, 1861) (Neuroptera: Chrysopidae) em casa-de-vegetação

Com esta pesquisa objetivou-se verificar o consumo de Uroleucon ambrosiae em diferentes densidades, por larvas de Chrysoperla externa provenientes de diferentes regimes alimentares, em casa-de-vegetação. Ninfas de 3º e 4º ínstares do afídeo foram separadas nas densidades 30, 40 e 50, e colocadas nas plantas de alface (35 dias de idade), as quais, foram envolvidas por gaiola de armação de ferro de 27x27x26 cm cobertas com tecido “voil” e acoplada nos tubos de PVC do cultivo hidropônico. Quatro horas após, uma larva de C. externa, de diferentes ínstares e previamente alimentadas com U. ambrosiae ou ovos de Sitotroga cerealella (Olivier, 1819), foi liberada próximo à colônia de afídeos, sendo a gaiola fechada imediatamente; o mesmo procedimento foi adotado sem que a larva fosse confinada. Após quarenta e oito horas, realizou-se a contagem do número de afídeos consumidos em cada densidade de presa disponível. A eficiência do predador, confinado em gaiola, foi de 12,46%, 13,63% e 25,76% para larvas de 1º, 2º e 3º ínstares previamente alimentadas com ovos de S. cerealella; 9,59% e 17,63% para aquelas de 2º e 3º ínstares alimentadas anteriormente com ninfas de U. ambrosiae, respectivamente e de 18,62% para larvas de 3º ínstar previamente alimentadas com ovos do lepidóptero no 1º ínstar e ninfas dos afídeos no 2º instar; no entanto, para larvas não confinadas, não foram verificadas diferenças significativas na eficiência. Nas densidades de 40 e 50 afídeos, as porcentagens de predação (18,30 e 18,72, respectivamente) foram significativamente superiores quando comparada à densidade 30 (11,79); para testes sem confinamento, não houve influência da densidade da presa na resposta do predador. Assim, o alimento fornecido às larvas de C. externa antes de serem liberadas em casa-de-vegetação, o confinamento das mesmas e a densidade de U. ambrosiae disponível influenciaram o potencial de consumo do predador.

Positive and negative effects of leaf shelters on herbivorous insects: linking multiple herbivore species on a willow.

We experimentally examined the effects on other herbivorous insects of leaf shelters constructed by lepidopteran larvae on a willow, Salix miyabeana. Several insect species occupied the vacant leaf shelters. Our experiment using artificial leaf shelters showed that the number of aphids increased with the number of artificial leaf shelters on a shoot, as did the numbers of three ant species ( Camponotus japonicus, Lasius hayashi, and Myrmica jessensis) that entered leaf shelters to collect aphid honeydew. To determine the ant-mediated effect of leaf shelters on herbivorous insects that do not use leaf shelters, we transferred newly hatched larvae of a common leaf beetle, Plagiodera versicolora, to the leaves of shoots with and without artificial leaf shelters. One day after the transfer, larval survival rate was significantly lower on shoots with shelters than on those without shelters, and shoots with shelters had significantly more ants than did shoots without shelters. Our field experiments demonstrated clearly that shelter-making lepidopteran larvae increased the abundance of both aphids and ants and decreased the survival rate of leaf beetle larvae, probably because the larvae were removed by ants that were attracted to the leaf shelters by the aphid colonies.

Oviposition Behavior ofOstrinia nubilalis(Lepidoptera: Crambidae) in Response to Potential Intra- and Interspecific Interactions

Abstract Oviposition behavior is an important mechanism for establishing spatial distribution and mitigating potential interactions among community members. We studied the oviposition behavior of the European corn borer, Ostrinia nubilalis Hubner, in the presence of conspecific larvae, the aphid Rhopalosiphum maidis (Fitch), and corn pollen to determine whether these potential interacting factors affect the distribution of European corn borer egg masses laid on sweet corn in field cages. We found that ovipositing females in the field differentiate between adjacent corn plants in response to conspecific larvae. We also found that European corn borers laid significantly fewer egg masses on plants with large aphid colonies compared with adjacent plants with few aphids. Furthermore, fewer egg masses were laid on the top one third of the plant where the aphid colonies were located. We also tested for a fitness advantage of European corn borer’s oviposition behavior in response to aphids and found that neonate ...

Population Dynamics Features of Willow-feeding Aphids

Willow-feeding aphid colonies were sampled on scattered trees (Salix alba) from April until November, in 1999. The collected individuals belonged to 9 aphid species of 3 families (Lachnidae, Chaitophoridae, Aphididae). The aphid populations showed two peaks in May and in October. The indirect negative effect of the rainfall seems to be responsible for this temporal pattern. The Shannon diversity also exhibited spring and autumn peaks during the year. The willow-feeding aphid guild seasonally rearranged, different species were dominant in each period. Four types of population dynamics of the 9 species were established based on the abundance changes. The time of appearance of different morphs in two dominant species was compared, they belonged to Pterocomma genus. In spring, there were uncoordinated schedule in the development of populations of P. pilosum konoi and P. rufipes, the different morphs of P. pilosum konoi increased earlier. In autumn both species reached their peaks simultaneously, but there were fewer individuals of P. pilosum konoi for a longer time. This species was more vulnerable to aphid parasitoids in each season.

The influence of female oviposition strategy on sibling cannibalism in the ladybird beetle Harmonia axyridis (Coleoptera: Coccinellidae)

I hypothesized that sibling cannibalism is one of maternal investment in that a female controls sibling cannibalism. To test the hypothesis, I conducted a laboratory experiment and field observations to investigate sibling cannibalism in relation to cluster size and cluster site in the ladybird beetle, Harmonia axyridis Pallas. In the laboratory experiment, cluster size significantly affected the number of cannibalized eggs per cluster (R2 = 0.516), while cluster size was significantly affected by the oviposition interval. Furthermore, there was a marginally significant positive relationship between cluster size and the percentage of sibling cannibalism per cluster. In the field, cluster size and the direct distance from a cluster site to an aphid colony (an indicator of intensity of non-sibling cannibalism) significantly affected the number of cannibalized eggs per cluster (R2 = 0.472). Furthermore, there was a significant positive relationship between the direct distance from a cluster to the nearest aphid colony and cluster size. However, there was not a significant relationship between the distance and the percentage of sibling cannibalism. These results may be caused by the weakness of the female's power to control sibling cannibalism. Thus, a female H. axyridis controls cluster size through the intensity of non-sibling cannibalism, which may be one of oviposition strategies in this species.

Different impacts of two species of aphid‐attending ants with different aggressiveness on the number of emerging adults of the aphid's primary parasitoid and hyperparasitoids

The impacts of two species of ants (Lasius niger and Pristomyrmex pungens) attending the cotton aphid (Aphis gossypii) on the number of emerging adults of the aphid's primary parasitoid (Lysiphlebus japonicus) and hyperparasitoids were assessed experimentally at a no‐pesticide mandarin grove. L. japonicus females were observed foraging frequently in aphid colonies attended by either ant species, with more females in P. pungens‐attended than in L. niger‐attended colonies, but rarely in aphid colonies where ants were artificially excluded. Females were less often attacked by P. pungens workers than by L. niger workers, so that they stayed longer and oviposited into more aphids in P. pungens‐attended than in L. niger‐attended colonies. Attendance by each ant species reduced predator numbers in aphid colonies, compared to colonies where ants were absent, although P. pungens was slightly less effective in repelling predators. Therefore, both ant species incidentally protected parasitized aphids from predators. Consequently, L. japonicus‐mummies were abundant in colonies attended by either ant species, with more mummies in P. pungens‐attended colonies, and were scarce in ant‐excluded colonies. The hyperparasitism and predation on L. japonicus larvae within mummies occurred more frequently in P. pungens‐attended than in L. niger‐attended colonies, but mummy predation rate was only 20% in the former. As a result, the number of emerging L. japonicus adults did not differ significantly between aphid colonies attended by the two ant species, but significantly more hyperparasitoids emerged in colonies attended by the relatively less aggressive P. pungens than in colonies attended by L. niger.

Experimental small‐scale grassland fragmentation alters aphid population dynamics

Theory predicts that at higher trophic levels species are especially vulnerable to habitat fragmentation due to small population size and dependence on particular prey species. Using aphids as model organism, we tested the hypothesis that herbivore abundance increases in fragmented habitats as a result of reduced predator and parasitoid densities. In a 3 year‐study, we examined the population dynamics of aphids with respect to host plant abundance and ant nest density in experimentally fragmented calcareous grasslands at two sites in the northern Jura mountains. Fragments of different size (area: 20.25 m2, 2.25 m2 and 0.25 m2) were isolated by a 5 m wide strip of frequently mown vegetation and corresponding control plots were situated in the adjacent undisturbed grassland. Aphid density was higher in fragments than in control plots. This was a combined result of a higher frequency of aphid‐infested plants and larger aphid colonies in fragments than in control plots. Furthermore, a larger proportion of aphid colonies was ant‐attended in fragments than in control plots. Aphid colonies were also more frequently visited by ants in fragments than in control plots in one of the 3 years. Parasitoid pressure on aphids was not influenced by the experimental fragmentation. Neither were aphid species richness and diversity affected by the fragmentation. Our study shows that even small‐scale habitat fragmentation can have profound effects on the abundance of herbivorous insects. The effect on aphid density was consistent over 3 years and two sites with slightly different aphid communities.

The interplay between density- and trait-mediated effects in predator-prey interactions: a case study in aphid wing polymorphism.

Natural enemies not only influence prey density but they can also cause the modification of traits in their victims. While such non-lethal effects can be very important for the dynamic and structure of prey populations, little is known about their interaction with the density-mediated effects of natural enemies. We investigated the relationship between predation rate, prey density and trait modification in two aphid-aphid predator interactions. Pea aphids (Acyrthosiphon pisum, Harris) have been shown to produce winged dispersal morphs in response to the presence of ladybirds or parasitoid natural enemies. This trait modification influences the ability of aphids to disperse and to colonise new habitats, and hence has a bearing on the population dynamics of the prey. In two experiments we examined wing induction in pea aphids as a function of the rate of predation when hoverfly larvae (Episyrphus balteatus) and lacewing larvae (Chrysoperla carnea) were allowed to forage in pea aphid colonies. Both hoverfly and lacewing larvae caused a significant increase in the percentage of winged morphs among offspring compared to control treatments, emphasising that wing induction in the presence of natural enemies is a general response in pea aphids. The percentage of winged offspring was, however, dependent on the rate of predation, with a small effect of predation on aphid wing induction at very high and very low predation rates, and a strong response of aphids at medium predation rates. Aphid wing induction was influenced by the interplay between predation rate and the resultant prey density. Our results suggests that density-mediated and trait-mediated effects of natural enemies are closely connected to each other and jointly determine the effect of natural enemies on prey population dynamics.

Entomophthoralean fungi associated with the common nettle aphid (Microlophium carnosum Buckton) and the potential role of nettle patches as reservoirs for the pathogens in landscape

AbstractPopulations of the common nettle aphid, Microlophium carnosum Buckton, inhabiting nettle patches in an agricultural landscape were surveyed for entomophthoralean infection during 1998, 1999 and 2001. Five pathogenic species were identified from the aphid in the course of the survey. Erynia neoaphidis Remaudière & Hennebert, Neozygites fresenii (Nowakowski) Remaudière & Keller, and Neozygites microlophii Keller affected aphid colonies every year. Two minor pathogens, Entomophthora planchoniana Cornu and Conidiobolus obscurus (Hall & Dunn) Remaudière & Keller, were observed only in 2001.An artificial transmission of the three main fungi was carried out to prove horizontal transmission of infection between the common nettle aphid and different aphid species co‐occurring in landscape. N. microlophii, probably monophagous pathogen, did not infect any of the six recipient aphid species in the experiment. Transmissions of E. neoaphidis and N. fresenii conidia were successful with five and four aphid species, respectively. The average mortality of tested aphids after transmission ranged from 0 to 33.33 % for E. neoaphidis and from 0 to 15 % for N. fresenii.The potential of nettle patches as natural reservoirs for pathogens in the agroecosystem is discussed.

Impacts of two ants, Lasius niger and Pristomyrmex pungens (Hymenoptera: Formicidae), attending the brown citrus aphid, Toxoptera citricidus (Homoptera: Aphididae), on the parasitism of the aphid by the primary parasitoid, Lysiphlebus japonicus (Hymenoptera: Aphidiidae), and its larval survival

The brown citrus aphid, Toxoptera citricidus, was attacked by the parasitoid Lysiphlebus japonicus, and was actively attended by two ant species, Lasius niger and Pristomyrmex pungens. The impacts of the two ants on the parasitism of the aphid by the parasitoid were assessed experimentally at a no-pesticide mandarin grove. Aphid colonies were artificially initiated on young citrus shoots in summer. Lysiphlebus japonicus females were frequently observed foraging in aphid colonies attended by P. pungens, but rarely in colonies attended by L. niger and colonies where ants were excluded. L. japonicus females were attacked by P. pungens workers, but oviposited successfully by avoiding the ants. Large predators were excluded by both ant species from the aphid colonies, while they were abundant in ant-excluded colonies. L. niger workers often carried living aphids away from the attended colonies, whereas P. pungens removed no aphids and disregarded parasitized aphids, thereby incidentally protecting the parasitized aphids from predators. Consequently, L. japonicus-mummies were formed in great numbers in colonies attended by P. pungens, but were scarce in colonies attended by L. niger and ant-excluded colonies. Aphid-attending P. pungens workers reduced predation and hyperparasitism on L. japonicus larvae within mummies. Thus, P. pungens attending T. citricidus largely enhances parasitism by L. japonicus and its larval survival, compared with when ants are absent, whereas L. niger exerts no remarkable impact.

Produção de formas aladas em colônias de Brevicoryne brassicae (L.) (Hemiptera: Aphididae) por indução do parasitóide Diaeretiella rapae (McIntosh) (Hymenoptera: Aphidiidae) e alguns aspectos comportamentais da interação destas espécies

O objetivo deste trabalho foi o de verificar se há indução de indivíduos alados em colônias de Brevicoryne brassicae (L.), quando expostas a Diaeretiella rapae (McIntosh). Foram também descritos alguns aspectos das interações biológicas dessas espécies. Colônias do pulgão foram iniciadas com 10 adultos por planta de couve, isoladas em recipientes transparentes. Um casal de parasitóides foi introduzido e mantido dentro de cada recipiente-teste por 3h; não foram introduzidos parasitóides do grupo controle. Formas aladas foram produzidas tanto na presença como na ausência de parasitóides, mas, na sua presença, os pulgões alados foram produzidos mais rapidamente e em número significativamente maior. Não se obteve correlação significativa entre o número de alados e o número de múmias. A longevidade média foi de 2,3 ± 0,19 dias e a taxa de parasitoidismo foi em média de 20,6 ± 5,21%. B. brassicae respondeu à presença de D. rapae com aumento na produção de formas aladas. Isto pode ser considerado um mecanismo de defesa, pois os pulgões poderiam, estrategicamente, manter sua sobrevivência, escapando pelo vôo e colonizando outras plantas hospedeiras. Dois outros comportamentos de defesas foram registrados: agitação vigorosa do corpo e fuga dos parasitóides. Durante 26h de observação, foram catalogados 20 atos comportamentais de D. rapae, divididos em cinco categorias: auto-limpeza, alimentação, exploração, cópula e oviposição. Interações diretas entre as espécies ocorreram não somente durante a oviposição, mas também quando a vespa tocava os pulgões com as antenas e ovipositor.

Aphid feeding damage causes large losses in susceptible lupin cultivars

The impact of infestation by bluegreen aphid, Acyrthosiphon kondoi, cowpea aphid, Aphis craccivora, and/or green peach aphid, Myzus persicae, on grain production of narrow-leafed lupin (Lupinus angustifolius) and yellow lupin (Lupinus luteus) was assessed at 4 sites in the Western Australian grainbelt. Yield losses caused by naturally occurring aphids on 4 cultivars of narrow-leafed and 2 cultivars of yellow lupins were measured by applying the systemic insecticide imidacloprid as a seed dressing and/or as foliar sprays throughout the plant growth phase and compared with untreated control plots. The extent of damage caused by aphids varied greatly but was significantly influenced by lupin cultivar, and yields for the same treatment combination varied between geographical locations. Bluegreen aphid was the most abundant species wherever large colonies of aphids developed. Yellow lupin Wodjil was the most infested and suffered severe losses in grain yield, whereas narrow-leafed lupin Kalya was largely resistant to aphids and there were negligible losses in grain production from plots not treated for aphids. In a fifth experiment, a single foliar spray of the insecticide pirimicarb controlled abundant aphids and increased yield by as much as 95% (0.65 t/ha) in Wodjil. Lupin growers need to be aware of the potential losses aphids can cause and that applying foliar insecticidal sprays to susceptible cultivars can prevent such losses.

Quantitative assessment of the infection rate of the entomophthoraceous fungus,Zoophthora anhuiensis against the green peach aphid Myzus persicae

A two-step method was developed to quantitatively assess the infection rate of the entomophthoraceous fungus,Zoophthora anhuiensis (Li) Humber, on the green peach aphid,Myzus persicae (Sulzer). Firstly, a standard time-dose-mortality relationship, established by modeling data from bioassay 1 at varying conidial dosages (0.4–10.4 conidia/mm2) ofZ. anhuiensis F97028, was used to yield an estimate of expected mortality probability at a given dosage. Secondly, biossay 2 was conducted by simultaneously exposing six ≤4-day-old nymphal colonies to a shower ofZ. anhueinsis conidia at each of four dosages (resulting from exposures of 0.3–8.0 min). Subsequently, the colonies were separately immersed in a 0.1% chlorothalonil solution for 0.5 min to disinfect all surviving conidia on the host integument from 1–12 h after exposure under temperature treatments of 15 and 20°C, respectively. The infection rate during a specific period from the end of the exposure to the immersion was then estimated as the ratio of the observed mortality over the expected mortality probability at a particular dosage. The results showed that the infection ofM. persicae fromZ. anhuiensis was highly rapid with little difference between aphid colonies maintained at 15 and 20°C before being immersed in the fungicidal solution after exposure. The first 6-hour period after exposure was most crucial to successful infection of the fungus with the infection rate greatly depending on conidial dosages. It took ≤1 h to infect >50% of the aphids at a dosage of >1.5 conida/mm2 and >90% at >50 conidia/mm2.