Aphidius Colemani Research Articles

Impact of differences in nutritional quality of wingless and winged aphids on parasitoid fitness.

Winged aphids are described as hosts of lesser quality for parasitoids because a part of their resources is used to produce wings and associated muscles during their development. Host lipid content is particularly important for parasitoid larvae as they lack lipogenesis and therefore rely entirely on the host for this resource. The goal of this study was to determine to what extent winged and wingless aphids differ from a nutritional point of view and whether these differences impact parasitoid fitness, notably the lipid content. We analysed the energetic budget (proteins, lipids and carbohydrates) of aphids of different ages (third instars, fourth instars and adults) according to the morph (winged or wingless). We also compared fitness indicators for parasitoids emerging from winged and wingless aphids (third and fourth instars). We found that in third instars, parasitoids are able to inhibit wing development whereas this is not the case in fourth instars. Both winged instars allow the production of heavier and fattier parasitoids. The presence of wings in aphids seems to have little effect on the fitness of emerging parasitoids and did not modify female choice for oviposition. Finally, we demonstrate that Aphidius colemani, used as a biological control agent, is able to parasitize wingless as well as winged Myzus persicae, at least in the juvenile stages. If the parasitism occurs in third instars, the parasitoid will prevent the aphid from flying, which could in turn reduce virus transmission.

Adaptation of Introduced Entomophages in the Insectarium of the Polar-Alpine Botanical Garden

As the result of a many-year experiment on adaptation of introduced entomophages in the specialized insectarium of the Polar-Alpine Botanical Garden (PABGI), populations of the following species have been established: Phytoseiulus persimilis Ath.-Henr., Amblyseius mckenziei Schuster et Pritchard, Aphidius matricariae Hal., Aphidius colemani Vier., Encarsia formosa Gahan, and Aphidoletes aphidimyza Rond. These populations have short periods of preimaginal development, are resistant to sharp temperature changes, very voracious and active. These acari- and entomophages can persist for a long time under the specific conditions of the greenhouse ecosystem, effectively control pests, and regulate the biocoenotic complex at the level meeting the phytosanitary requirements. In their ecological characteristics the PABGI cultures surpass the conspecific populations from more southern areas.

Cereal Aphid Species (Homoptera : Aphididae) Infesting Wheat Plants and their Aphidophagous Insects at El-Khattara District, Sharkia Governorate, Egypt

Studies on cereal aphids infesting wheat plants and their aphidophagous insects were carried out in newly reclaimed sandy area at El-Khattara district, Sharkia Governorate, Egypt during 2015-2016 and 2016-2017 growing seasons.The obtained results are summarized as follows:Four aphid species, i.e., Shizaphis graminum (Rondani), Rhopalosiphum maidis (Fitch), Rhopalosiphum padi (Linnaeus) and Macrosiphum avenae (Fabricius) were found infested wheat plants.Cereal aphids infested wheat plants from the first week of January till the last week of April. The highest populations of aphids were recorded in the first week of March and in the second week of April with counts of 711 and 1503 individuals/ sample in the first and second seasons, respectively.Six predaceous insect species belonging to four orders and five families were surveyed associated with aphid species infesting wheat plants. Coleopterous species were the most dominant, followed by the neuropterous ones, with general relative densities of 41.70 and 21.10 % of the total recorded predators, successively. Among all recorded predaceous species, Chrysoperla carnea (Stephens) , Coccinella undecimpunctat L., and Coccinella septempunctata L., were the most dominant species, comprised 21.10, 15.68 and 15.26 % of the total count of the predators, respectively. The total recorded predators showed that means of 1:61.62 and 1:118.73 predators: prey ratios in the first and second seasons, respectively.Five species of hymenopterous parasitoids were emerged from mummified individuals of cereal aphids, namely, Diaeretiella rapae (M’Intosh), Aphidius colemani Viereck, Aphidius matricariae Haliday, Ephedrus sp. and Praon sp. The most dominant parasitoids were D. rapae and A. colemani with general relative densities of 35.32 and 27.12% respectively. The fluctuations of the total percentages of parasitism indicated three peaks in the first season and two ones in the second season. The mean percentage of parasitism during the first season was relatively high (6.41%) in comparison with that in the second one (3.60%).The correlation between cereal aphids populations and percentages of parasitism in both seasons were positive high significant

Toxicities of 26 pesticides against 10 biological control species

To determine selective effectiveness for specific pesticides on biological control species we evaluated the contact toxicity of 16 insecticides, 2 acaricides, 3 fungicides, and 5 biopesticides. Targeted species included 3 predatory mites (Phytoseiulus persimilis Athias-Henriot, Amblyseius swirskii Athias-Henriot, and Neoseiulus californicus McGregor), 5 hymenopteran parasitoids (Diglyphus isaea Walker, Aphidius colemani Viereck, Encarsia formosa Gahan, Eretmocerus eremicus Rose and Zolnerowich and E. mundus Mercet), and 2 hemipteran predators (Orius laevigatus Fieber and Nesidiocoris tenuis Reuter) in laboratory condition. In addition, residual toxicity was evaluated on P. persimilis, E. formosa, and O. laevigatus. For contact toxicity, five insecticides (spinetoram, spinosad, lepimectin, chlorfenapyr, and dinotefuran+spinetoram) showed high toxicity to predatory mites. Most pesticides tested were highly toxic to all hymenopteran species except for D. isaea which showed low susceptibility to 11 pesticides. Bistrifluron+flubendiamide and B. valismortis were less toxic to A. colemani, and only B. valismortis was safe to both E. mundus and E. eremicus. Insect growth regulators (methoxyfenozide and bistrifluron), chlorantraniliprole, and bistrifuron+flubendiamide were not toxic to hemipteran predators. Fungicides and biopesticides were safe to hemipteran predators except for two biopesticides (B. subtilis and P. fluorescens). Most pesticides had low residual toxicity to P. persimilis, with the exception of chlorfenapyr whose toxicity persisted over 7days. One insecticide (cyantraniliprole), 2 acaricides (spiromesifen and fenpyroximate), 1 fungicide (metrafenone), and 4 biopesticides (B. subtilis, P. polymyxa, P. fluorescens, and B. valismortis) showed a much lower residual toxicity to E. formosa. Eight insecticides, 2 acaricides, 3 fungicides, and 5 biopesticides showed low residual toxicity to O. laevigatus.

Efficacy of a new slow-release volatile system against Aphis gossypii Glover (Hemiptera: Aphididae) on cucumber, Cucumis sativus L.

Many arthropod agricultural pests have become resistant to pesticides through inappropriate usage. A consequence of this resistance is often cross-resistance with other pesticides with similar or related modes of actions. As a result of increasing pesticide resistance, a movement to alternative, ‘green’ botanical pesticides has been growing. A new formulation of volatile oils, extracted from a variety of plants allows for slow-release and longer duration in the field. In this publication we present results of the efficacy of one of these products against the cotton aphid Aphis gossypii on cucumber plants in replicated choice tests. The slow release Ap2, a Bio-Pel product from Newseal Mineral and Coatings Ltd. (hereafter Newseal), significantly reduced the population of aphids on test plants and prevented their movement upwards on the plant. Additionally, four Newseal products caused no mortality to the aphid parasitoid Aphidius colemani or to the generalist predator, Orius laevigatus.

Plant virus infection influences bottom-up regulation of a plant-aphid-parasitoid system

Plant viruses strongly influence the physiology of their host plants and phytophagous insect vectors, thereby affecting ecological interactions between them. Despite the important role of natural enemies on insect vector control and thus on virus dissemination, the influence of plant viruses on the third trophic level received little attention. We investigated how infection of the plant Camelina sativa (Brassicaceae) by the Turnip yellows virus (TuYV) influenced the host plant, an aphid vector (Myzus persicae) and an aphid parasitoid (Aphidius colemani) through bottom-up effects on the physiology of the three trophic levels. We also considered the behavioural responses of A. colemani towards infected and control (uninfected) plant-aphid complexes. Highlighting the importance of virus infection on bottom-up regulation of tri-trophic systems, TuYV infection resulted in (1) decreased photosynthetic activity and biomass in C. sativa, (2) an improvement of some aphid fitness parameters important for population dynamics and virus dissemination (i.e. better nymphal survival and shorter pre-reproductive period), but (3) a decrease in some other aphid parameters (i.e. lower body size and quantity of stored energetic resources), which probably explained (4) the decrease in several fitness-related traits (i.e. body size, fecundity and lipid content) in parasitoids developing in aphids reared on infected plants. Female parasitoids showed similar attraction towards control and infected plants, and similar attack and rejection rates towards control and virus-infected aphids. Our results suggest that in agroecosystems, virus presence may reduce parasitoid abundance and consequently biological control of aphid vectors, impacting virus dissemination and plant damage.

Gustatory response and longevity in Aphidius parasitoids and their hyperparasitoid Dendrocerus aphidum

Aphid parasitoids are commonly used in the biological control of aphids. However, their success in biological control largely depends on the availability of carbohydrate-rich food as an energy source for maintenance and reproduction. Therefore, as these resources have become rare in modern agricultural systems, external sugar sources like flowering plants or artificial sugar solutions are more and more used to provide the biocontrol agents with the necessary sugars. When developing such artificial food sources, it is essential to carefully select the sugars that best support the target parasitoids without benefiting non-target insects, such as pest insects or hyperparasitoids. Here, we investigated the gustatory response and longevity of two commonly used aphid parasitoids (Aphidius colemani and Aphidius matricariae) and their hyperparasitoid Dendrocerus aphidum when provided with one of eight plant- and/or insect-derived sugars (fructose, galactose, glucose, melibiose, melezitose, rhamnose, sucrose and trehalose). Our results showed that the studied insect species consumed the largest amounts of sugars that are most commonly found in honeydew (sucrose, fructose, glucose and melezitose) and also survived best when feeding on these sugars. Both Aphidius spp. survived well on melibiose, whereas D. aphidum performed poorly on this sugar. When melibiose was offered in a mixture with glucose, a significant reduction in longevity was observed for D. aphidum when compared to glucose only, while this was less pronounced for Aphidius spp. This knowledge can be exploited in tailoring food sources to selectively support Aphidius parasitoids, enhancing the biological control of aphids.

An evaluation of the effect of botanical insecticide, palizin in comparison with chemical insecticide, imidacloprid on the black citrus aphid, Toxoptera aurantii Boyer de Fonscolombe and its natural enemy, Aphidius colemani Viereck

AbstractThe black citrus aphid,Toxoptera aurantiiBoyer de Fonscolombe (Hemiptera: Aphididae), an important pest of citrus species, feeds by sucking sap from plant leaves. It causes some leaf distortion and malformation of growing leaves and shoot tips. In this study, the effects of the botanical insecticide, palizin onT. aurantiiand its parasitoid,Aphidius colemaniViereck (Hymenoptera: Brachonidae) were compared with the chemical insecticide, imidacloprid. The compounds were evaluated at maximum recommended field concentrations: palizin 2,000 ppm, imidacloprid 500 ppm, water (as control) on adult aphids. Spraying was done with a 100-l engine Honda sprayer (GX120T1, 160T1, 200T) until run-off. The number of dead aphids was recorded 24, 48 and 72 hours after treatment. According to the results, statistically significant differences were found between treatments (p ≤ 0.05). Twenty-four hours after treatment, imidacloprid was more effective than palizin in reducing theT. aurantiipopulation. Palizin showed high efficiency (95% mortality) 72 hours after treatment. However, at that time, there was no statistically significant difference between the mean mortality percentages of imidacloprid and palizin. This shows that botanical insecticide, palizin can effectively controlT. aurantii. Also, palizin caused low mortality (10.86%) onA. colemaniwhile imidacloprid was more toxic (31.1% mortality). The results of the present study indicated that palizin can be used instead of chemical insecticide, imidacloprid in control programs ofT. aurantii.

Effective Biological Control Depends on Life History Strategies of Both Parasitoid and Its Host: Evidence from Aphidius colemani-Myzus persicae System.

Mechanisms behind the success and failure of aphid biological control using parasitoids are largely unknown, probably because of the lack of knowledge of life history strategies of the insects involved. Here, we measured and compared life history strategies of Myzus persicae (Sulzer) (Hemiptera: Aphididae) and its parasitoid Aphidius colemani (Viereck) (Hymenoptera: Aphidiidae), providing essential information for evaluation of the potential of A. colemani to control M. persicae. Our results show that one A. colemani female parasitized ≈220 aphids within 1 wk regardless of the aphid age. Almost all aphids parasitized at <4th instar died before reaching adulthood, and those parasitized at ≥4th instar produced very few offspring, contributing little to population growth. Although having 21% lower intrinsic rate of increase and 33% longer life cycle than the aphid, the parasitoid possessed reproductive output and net population growth rate twice as high as the aphid, and reached maximum lifetime reproductive potential 1 wk earlier than the aphid. The life history strategies reported here imply that A. colemani is potentially a good biological control agent of M. persicae. On the basis of this study, we hypothesize that immediately after the onset of M. persicae, a release rate of ≈1:220 (female parasitoid:aphids) at a weekly interval during the first 3 wk could effectively control the pest. We suggest that the success of biological control of aphids using parasitoids largely depends on life history strategies of both insects involved and time of the season when they meet.

Mechanisms Underlying the Nonconsumptive Effects of Parasitoid Wasps on Aphids.

Natural enemies need not consume herbivores to suppress herbivore populations. Behavioral interactions can adversely impact herbivore fitness from reduced time feeding, investment in defense, or injury from failed attacks. The importance of such "nonconsumptive effects" for herbivore suppression may vary across species based on the specificity and intensity of the herbivore defensive response. In a series of manipulative studies, we quantified the nature and consequences of nonconsumptive interactions between two parasitoid wasps, Aphidius ervi Haliday and Aphidius colemani Viereck, on two aphid species, pea aphids (Acyrthosiphon pisum (Harris)) and green peach aphids (Myzus persicae (Sulzer)). Both wasps successfully parasitize green peach aphids, but only A. ervi parasitizes pea aphids. We observed A. ervi antennating and stinging pea aphids and documented a decrease in pea aphid longevity in response to stinging even when the aphid survived the interaction and no mummy formed. The primary defensive tactic of pea aphids in response to either wasp species was dropping from the host plant. Both wasp species antennated and stung green peach aphids, but they elicited unique defensive behaviors. Green peach aphids kicked or emitted cornicle secretions in response to A. colemani but spent more time off the plant in the presence of A. ervi. Green peach aphid longevity and fecundity were not affected by wasp stings when the aphid survived and no mummy formed. Our study demonstrates the complexity of behavioral interactions between parasitoids and their potential hosts and contributes to a mechanistic understanding of variation in the nonconsumptive suppression of herbivore populations.

Host plants and aphid hosts influence the selection behaviour of three aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae)

Aphis fabae and Myzus persicae (Hemiptera: Aphididae) are insect pests that damage sugar beet and bean crops. Both are responsible for losses in yield and transmission of viral diseases, and may be present on the same host at the same time. Three parasitoid species, Aphidius colemani, Lysiphlebus testaceipes and Lysiphlebus fabarum (Hymenoptera: Braconidae: Aphidiinae) have the potential to be used as biological control agents against at least one of these species of aphids. As a first step prior to the implementation of a biological control program, our aim was to understand the host selection behaviour of the parasitoids, particularly when both aphids are present. We recorded the host acceptance (number of insertions of the ovipositor / number of antennal contacts), suitability (number of mummies / the number of insertions of the ovipositor) and emergence (number of adults emerging from mummies) of these three aphid parasitoids when parasitizing the two aphids. We also analyzed the effect of the host plant on the host preference of the parasitoid. Females of each parasitoid species (n = 15) were exposed to 20 aphids of A. fabae or M. persicae, or a mixture of these two species of aphids, for 15 min, on a leaf disc of each of the two host plants, sugar beet and bean. Higher host acceptance and suitability were recorded for A. colemani attacking both species of aphid: A. fabae (43 and 46%) and M. persicae (43 and 46%) on beet and bean plants respectively, compared to L. testaceipes and L. fabarum. L. testaceipes and L. fabarum showed a clear preference for A. fabae. L. fabarum accepted M. persicae on both plants only when it was mixed with A. fabae, probably due to a confusion effect. We found that the host plant played a significant role in host acceptance, host suitability. We conclude that A. colemani is the better of the three parasitoids studied for the biological control in bean, and particularly, sugar beet crops.

Relative toxicity of insecticides to the crucifer pests Plutella xylostella and Myzus persicae and their natural enemies

The widespread and intensive use of conventional pesticides, particularly insecticides, presents a major risk to natural enemies of target pests, as well as to the environment in general. The aim of this study was to investigate the differential intrinsic toxicity of insecticides to two key pests of crucifers, Plutella xylostella and Myzus persicae and their respective hymenopteran parasitoids, Cotesia vestalis and Aphidius colemani. Such knowledge can help inform effective integration of insecticides and biological control in IPM systems. Three insecticides generally regarded as being compatible with natural enemies (abamectin, spinosad and indoxacarb) and one compound regarded as harmful to natural enemies (lambda-cyhalothrin) were examined. A comparative measure of the intrinsic toxicity of fresh deposits of insecticides on Chinese cabbage leaf discs was determined for both pest and parasitoids species after exposure to insecticide for 24 h and 120 h, and after 24 h exposure to insecticide plus 96 h on untreated leaf discs. Differences in the susceptibility of pests and parasitoids to different insecticides were marked for P. xylostella and C. vestalis, LC50 values being significantly lower for the pest species. Such differences were not observed for M. persicae and A. colemani. There was a direct relationship between dose, exposure time and toxicity for all insecticides tested. All insecticides tested showed lower toxicity to both parasitoids compared with P. xylostella, which suggests that for this pest species side-effects on parasitoids can be minimised through IPM practices that reduce exposure time to such non-target organisms.

Trade-Off Between Fitness Gain and Cost Determines Profitability of a Peach Aphid Parasitoid.

Aphidius colemani (Viereck) (Hymenoptera: Aphidiidae) is commercially produced and utilized for biological control of peach aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae) on greenhouse crops in many countries. To provide knowledge for the evaluation of parasitoid-host interactions and development of effective mass rearing programs, we investigated how and why host age or size affected fitness gain in A. colemani We show that the parasitoid was significantly more likely to encounter larger hosts and that an encounter almost always triggered an attack attempt. However, the attack attempt did not proportionally translate into oviposition because larger aphids had greater ability to defend themselves and the parasitoid spent more time in handling larger aphids. The host age at parasitization had no effect on emergence rates and sex ratio of parasitoid progeny, suggesting that pupae and larvae have similar survival rate in hosts of different ages and/or the parasitoid females do not adjust sex allocation based on host size. When parasitizing mid-aged hosts, the parasitoid gained maximum fitness for their progeny in developmental period, body size, and parasitism. Taking all findings together, we suggest that parasitizing mid-aged green peach aphid nymphs is most profitable for A. colemani.

Olfactory response of four aphidophagous insects to aphid- and caterpillar-induced plant volatiles

Plants damaged by herbivores emit blends of volatile organic compounds (VOCs) that attract the herbivore’s natural enemies. Most work has focussed on systems involving one plant, one herbivore and one natural enemy, though, in nature, plants support multiple herbivores and multiple natural enemies of these herbivores. Our study aimed to understand how different aphid natural enemies respond to aphid-induced VOCs, and whether attraction of the natural enemies that responded to aphid-induced VOCs was altered by simultaneous damage by a chewing herbivore. We used a model system based on Brassica juncea (Brassicaceae), Myzus persicae (Hemiptera: Aphididae) and Plutella xylostella (Lepidoptera: Plutellidae). Ceraeochrysa cubana (Neuroptera: Chrysopidae) did not show preferences for any plant odour, while Cycloneda sanguinea (Coleoptera: Coccinellidae) responded to undamaged plants over air but not to aphid-damaged plants over undamaged plants. Therefore, no further tests were carried out with these two species. Chrysoperla externa (Neuroptera: Chrysopidae) preferred aphid-damaged plants, but not caterpillar-damaged plants, over undamaged plants, and preferred plants damaged by both herbivores over both undamaged plants and aphid-damaged plants. When tested for responses against undamaged plants, Aphidius colemani (Hymenoptera: Braconidae) preferred aphid-damaged plants but not plants damaged by caterpillars. Plants damaged by both herbivores attracted more parasitoids than undamaged plants, but not more than aphid-damaged plants. Thus, multiply damaged plants were equally attractive to A. colemani and more attractive to C. externa than aphid-damaged plants, while C. cubana and C. sanguinea did not respond to aphid-induced VOCs, highlighting how different natural enemies can have different responses to herbivore-damaged plants.

Comparative selectivity of pesticides used in greenhouses, on the aphid parasitoid Aphidius colemani (Hymenoptera: Braconidae)

ABSTRACTA series of bioassays were conducted under laboratory conditions to determine the relative toxicities of various pesticides (acetamiprid, cypermethrin, chlorantraniliprole and emamectin benzoate, Bacillus thuringiensis var. kurstaki and Helicoverpa armigera nucleopolyhedrovirus, copper oxychloride, iprodione, mandipropamid, a mixture of propamocarb + fluopicolide and mixture of fludioxonil + cyprodinil) on Aphidius colemani adults and mummies, as well as sublethal effects on female fecundity. Cypermethrin was highly toxic to pupa of A. colemani within host mummies. Acetamiprid, cypermethrin, emamectin benzoate, a mixture of propamocarb + fluopicolide and mixture of fludioxonil + cyprodinil were also highly toxic to A. colemani adults (92–100% mortality at 48 h post treatment). Mandipropamid, iprodione and copper oxycloride treatments significantly reduced fecundity of the female parasitoids. In contrast B. thuringiensis var. kurstaki, H. armigera nucleopolyhedrovirus and chlorantraniliprole were harmless (<30% mortality) to the parasitoid species tested according to International Organisation for Biological Control toxicity classification and are likely to be compatible with integrated pest management programmes.

Differences in the reproductive durations of Myzus persicae (Hemiptera: Aphididae) parasitized by three aphidiid parasitoids

The reproductive durations of Myzus persicae (Sulzer) after parasitization by three species of Aphidiinae were compared and the mechanisms for differences in duration were examined. The lifetime fecundities of adult aphids parasitized by Aphidius colemani Viereck, Aphidius gifuensis Ashmead, and Diaeretiella rapae (McIntosh) were 3.96, 6.40, and 6.48, respectively. These values were much smaller than that of healthy adults (61.43 nymphs). The time of termination of reproduction by the aphids coincided with the time that the parasitic wasp larvae reached second instar. We infer that first-instar larvae of all three species initially attack conspecific and/or heterospecific competitors and that consumption of the aphid’s ovaries and other reproductive organs commences in the second instar. The modified intrinsic rates of natural increase (rparasitized) calculated from post-parasitized fecundity were 0.185 by A. colemani, 0.233 by A. gifuensis, and 0.234 by D. rapae. Parasitization of 100 % of the adult aphids by A. gifuensis or D. rapae decreased the growth rate to a minimum of 24.4 % while A. colemani more moderately suppressed the growth of the aphid population (39.9 %). We propose the possibility that the effectiveness of species of Aphidiinae as biological control agents is influenced by differences in the duration of aphid reproduction following parasitization.

Fitness Effects of Food Resources on the Polyphagous Aphid Parasitoid, Aphidius colemani Viereck (Hymenoptera: Braconidae: Aphidiinae).

Conservation biological control involving the polyphagous aphid parasitoid, Aphidius colemani Viereck, may include provisioning resources from a variety of plant sources.The fitness of adult A. colemani was enhanced with the provision of food resources such as floral nectar from a range of both native and introduced plant species and aphid honeydew under laboratory conditions. However, enhanced fitness appeared to be species specific rather than associated with the whether the plant was a native or an introduced species. Parasitoid survival and fecundity were enhanced significantly in response to the availability of floral nectar and honeydew compared to the response to available extrafloral nectar. These positive effects on the parasitoid’s reproductive activity can improve the effectiveness of conservation biological control in nursery production systems because of the abundance and diversity of floral resources within typical production areas. Additionally, surrounding areas of invasive weeds and native vegetation could serve as both floral resources and honeydew food resources for A. colemani.

The toxic effect of camphor vapour against Aphis craccivora Koch (Hemiptera: Aphididae) and some of its natural enemies

Fumigant toxicity of camphor was studied against the aphid Aphis craccivora Koch and three associated natural enemies, i.e. Coccinella undecimpunctata L., Aphelinus albipodus Hayat & Fatima and Aphidius colemani Viereck. Aphis craccivora was the most tolerant one compared with all tested natural enemies as the recorded LC50 values were 12.71, 6.33, 1.16 and 0.48 mg camphor/liter space for the above mentioned insects, respectively. Subjecting newly emerged adults of A. craccivora to LC25 of camphor vapor significantly reduced female longevity from 17.6 to 6.45 days and reduced the female daily progeny from 4.44 to 1.93 nymph / female, which resulted in a reduction in productivity as finite rate of increase decreased from 1.57 to 1.14 female / female / day. Aphids that survived after subjection to LC50 were found to have significantly higher amount of acid phosphatase and G. S-transferase than non-treated aphids. Inversely, Survived aphids were found to have significantly less amount of β-esterases and alkaline phosphatase than nontreated aphids; while no significant difference was found in case of α-esterases. Camphor fumigant can be a candidate as a control agent against A. craccivora but with restriction because of its drawbacks on natural enemies.

Grain Diversity Effects on Banker Plant Growth and Parasitism by Aphidius colemani.

Green peach aphid (Myzus persicae Sulzer) (Hemiptera: Aphididae) is a serious greenhouse pest with a short generation time, parthenogenetic reproduction and a broad host range. Banker plant systems are becoming a more common form of biological control for this pest. This system consists of grain “banker plants” infested with R. padi, an alternative hosts for the parasitoid Aphidius colemani. Thus A. colemani can reproduce on the banker plant when M. persicae populations are low. This system can increase pest suppression; however, like other biological control tools, efficacy is inconsistent. One reason is because several different grain species have been used. Our studies determined if there were benefits to planting interspecific mixture banker plants, similar to when open agricultural systems use mixed cropping. Our study found that although banker plants grow larger when planted as mixtures this added plant growth does not increase in the number of aphids, or mummies an individual banker plant can sustain. Rye banker plants grew larger, and sustained more mummies than the other species we tested, but barley banker plants resulted in a similar number of aphids in a more condensed area. Ultimately, we did not see any differences in pest suppression between monoculture banker plants, mixture banker plants, or our augmentative release treatment. However, using banker plants resulted in more female parasitoids than the augmentative release, a benefit to using banker plant systems.

Aphidophagous parasitoids can forage wheat crops before aphid infestation, Parana State, Brazil.

Aphid parasitoids are common in Brazilian wheat fields, and parasitize aphids at the wheat tillering stage. However, there is little information available about when this natural enemy occurs in wheat crops. This study investigated the initial occurrence of aphid parasitoids in four commercial wheat crops in northern Paraná during the 2009 crop season. We installed two Malaise traps at each wheat farm, and 400 tillers were assessed weekly in each field for aphid abundance. During this study, we captured 4,355 aphid parasitoids and 197 aphids. Three species of braconid parasitoids were identified, including Aphidius colemani (Viereck 1912), Lysiphlebus testaceipes (Cresson 1880), and Diaeretiella rapae (McIntosh 1855). The aphids species identified were Rhopalosiphum padi (Linnaeus 1758) and Sitobion avenae (Fabricius 1775). This study showed that aphid parasitoids are present in wheat crops even when aphid densities are low, and in one farm, occurred before the aphids colonization. These reports can justified the high efficiency of these natural enemies against aphids in wheat fields.