Brachycaudus Helichrysi Research Articles

Effect of indigenous aphids on the development of invasive common ragweed,Ambrosia artemisiifolia(L.) in Hungary

The common ragweed, Ambrosia artemisiifolia (L.), is a widespread invasive weed species in Europe. In order to estimate the hampering effect of native arthropods on the invasive ragweed, the effect of three indigenous aphid species on plant development and pollen production was studied. Common ragweed plants grown in a greenhouse were artificially infested with five apterous individuals of either Aphis fabae Scopoli, Brachycaudus helichrysi (Kaltenbach) or Myzus persicae (Sulzer) at the 4-leaf stage. Feeding by all three aphid species over a five-week period significantly reduced plant height, the number of male inflorescences, the length of racemes, pollen emission and plant dry weight. Brachycaudus helichrysi produced the largest colonies, followed by A. fabae and M. persicae. In a field experiment, the growth rate of A. fabae on caged ragweed plants was similar to that in the greenhouse, but the final numbers of B. helichrysi and M. persicae after 30 days was ten and seven times lower, respectively tha...

The Sex Pheromones of Mealy Plum (Hyalopterus pruni) and Leaf-Curl Plum (Brachycaudus helichrysi) Aphids: Identification and Field Trapping of Male and Gynoparous Aphids in Prune Orchards

Mealy plum, Hyalopterus pruni, and leaf-curl plum, Brachycaudus helichrysi, aphids are the primary arthropod pests in orchards that produce dried plums (i.e., prunes). The sexual stage of their respective lifecycles occurs on prune trees in the fall, during which time males respond to sex pheromones produced by oviparous females. Air-entrainment collections confirmed that oviparous H. pruni and B. helichrysi emitted combinations of (4aS, 7S, 7aR)-nepetalactone and (1R, 4aS, 7S, 7aR)-nepetalactol. The responses of H. pruni and B. helichrysi to these compounds in ratios of 1:0, 0:1, 1:1, 2.6:1, 3.4:1, 5:1, 7:1, and 0:0 (no-pheromone control) using water traps were determined in field experiments conducted in prune orchards during the fall. The greatest number of male H. pruni was caught in traps releasing a 1:1 ratio of (4aS, 7S, 7aR)-nepetalactone and (1R, 4aS, 7S, 7aR)-nepetalactol, while male B. helichrysi were caught in similar numbers in traps releasing any of the two-component ratios tested. There was no evidence that any of the pheromone treatments influenced trap catches of gynoparae of either species. Results suggest that addition of sex pheromone lures increases trap catches of male H. pruni and B. helichrysi, and that this approach may improve monitoring and management of these pests in prune orchards. Knowledge gained from this study contributes to the understanding of the ecology of insect pests in prune orchards.

A survey on pest insect fauna of safflower fields in the Iranian Province of Kohgiloyeh and Boyerahmad

Safflower ( Carthamus tinctorius L.) is an important oilseed crop and an essential component of cropping systems in the dry regions and marginal areas of the world. Since the identification of insect pests and their natural enemies is one of the most efficient methods for pest management, an attempt was made to investigate insect fauna in safflower fields of Kohgiloyeh and Boyerahmad Provinces, Iran. To accomplish this, three main cultivation regions were selected and insect pests and their natural enemies were surveyed and collected according to the plant phenology during 2008 to 2009. To sample different techniques, such as sweeping, sticky yellow traps, bait traps and rearing of adult insects, were used. Pest insect fauna was as follows: 1) Pest insects feeding inside the flower heads (bolls) and their natural enemies: Acanthiophilus helianthi , Chaetorellia carthami , Trellia luteola (Tephritidae), Antistrophoplex conthurnatus , Microdontomenu annulatus (Torymidae), Bracon hebetor , Bracon luteator (Braconidae); unidentified specimen (Ichneumonidae), Pronotalia carlinarum (Eulophidae), Ormyrus orientalis (Ormyridae), Colotrechnus viridis , Pteromalus sp. (Pteromalidae), Eurytoma acroptilae (Eurytomidae); Isocolus tinctorius (Cynipidae). 2) Pest insects feeding around the flower heads (bolls) and their natural enemies: Oxycarenus palens , Oxycarenus hyalipennis , Lygus spp. (Lygaeidae), unidentified specimens (Dermestidae), Aphids and Thripses. 3) Pests insects feeding on other parts and their natural enemies: Uroleucon compositae , Pleotrichophorus glandolosus , Brachycaudus helichrysi (Aphididae), Lysiphlebus fabarum (Braconidae), Pachyneuron concolor (Pteromalidae), Coccinella septempunctata , Hippodamia variegata (Coccinellidae), Orius spp. (Anthocoridae); Chrysoperla carnea (Chrysopidae); Neoaliturus fenestratus , Euscelis alsius , Macrosteles laevis , Psammotettix striatus , Circulifer haematoceps (Cicadellidae); Reptalus bitinctus (Cixiidae), Thrips tabaci (Thripidae); Aeolothrips collaris (Aeolothripidae); Haplothrips sp. (Phlaeothripidae), Chromatomyia horticola (Agromyzidae), Agrotis sp., Helicoverpa peltigera (Noctuidae). The results indicate that various insect pests and their natural enemies are active in the safflower fields, and that their identification is very important for various control methods.

POSSIBILITY OF REDUCING CHEMICAL TREATMENTS AIMED AT CONTROL OF PLUM INSECT PESTS

During the last two years the main insect pests on plum trees in the region of Plovdiv (Central-South Bulgaria) were black and yellow plum sawflies (Hoplocampa minuta and H. flava) that destroyed 68-84% of fruitlets after bloom. Red plum maggot (Grapholitha funebrana) damaged more than 24-32% of fruits. Other important pests were two aphids (Hyalopterus pruni and Brachycaudus helichrysi), infesting 86-95,3% of shoots and brown scale (Parthenolecanium corni). Leaf sawfly (Neurotoma nemoralis), fall webworm (Hyphantria cunea), and plum ermine moth (Yponomeuta padellus) caused significant damage on leaves too. Some secondary pests, such as weevils, Rhynchites sp. and Phyllobius sp. as well as pear lace-bug (Stephanitis pyri) and others, damaged buds, fruits and leaves. Plant protection systems recommended for control of plum pests commonly include 10-12 chemical treatments. The experiments carried out in the orchards of the Agricultural University - Plovdiv have shown that the number of treatments may be significantly reduced without any negative effect on the trees or on the crop quantity and quality. This can be done by optimisation of the date of treatments, selection of proper insecticides and use of pheromones for mating disruption.

Studies on the aphids (Hemiptera: Aphididae) and their natural enemies on peach orchards in İzmir.

Field surveys were carried out during 2008 in order to report the results of survey of aphid species, their natural enemies and distribution in some peach orchards in Izmir province. In addition, this work has gained importance after Plum Pox Virus previously detected in stone fruits in Izmir, because aphids are important vectors of the disease. For this purpose samples were taken from Bayindir, Bergama, Bornova, Kemalpasa, Menemen, Odemis, Selcuk, Tire and Torbali districts of Izmir. Aphid species determined were Brachycaudus helichrysi (Kaltenbach, 1843), Hyalopterus pruni (Geoffroy, 1762), Myzus (Nectarosiphon) persicae (Sulzer, 1776) and Pterochloroides persicae (Cholodkovsky, 1899) (Hemiptera: Aphididae). The Infested buds percentage in minimum and maximum were found to be 3% and 85%, respectively in the orchards. Coccinella septempunctata Linnaeus, 1758, Adalia bipunctata (Linnaeus, 1758), A. decempunctata (Linnaeus, 1758), Oenopia conglobata (Linnaeus, 1758), Hippodamia variegata (Goeze, 1777) (Coleoptera: Coccinellidae), Episyrphus balteatus (De Geer, 1776), Eupeodes (Metasyrphus) corollae (Fabricius, 1794), Ischiodon scutellaris (Fabricius, 1805), Scaeva pyrastri (Linnaeus, 1758) (Diptera: Syriphidae), Leucopis annulipes (Zetterstedt, 1848) (Diptera: Chamaemyiidae) and Chrysoperla carnea (Stephens, 1836) (Neuroptera: Chrysopidae) were found as predators and Aphidius colemani Viereck, 1912, Aphidius matricariae Haliday, 1834, Aphidius transcaspicus Telenga, 1958, Diaeretiella rapae (McIntosh, 1855) and Ephedrus persicae Froggatt, 1904 (Hymenoptera: Braconidae) were determined as parasitoids of aphids.

Impact of indigenous aphids on development of the invasive common ragweed (Ambrosia artemisiifolia L.) in Hungary

The common ragweed, Ambrosia artemisiifolia is a widespread invasive weed species in Europe. In order to estimate the deteriorative effect of native arthropods on the invasive ragweed the effect of three indigenous aphid species on plant development and pollen production was studied. Common ragweed plants grown in a greenhouse were artificially infested with five apterous individuals of either Aphis fabae, Brachycaudus helichrysi or Myzus persicae at the 4-leaf stage. Feeding by all three aphid species over a 5-week period significantly reduced plant height, the number of male inflorescences, the length of racemes, pollen emission and plant dry mass. Brachycaudus helichrysi produced the largest colonies, followed by A. fabae and M. persicae. In a host plant choice test, B. helichrysi showed significant preference for ragweed over sunflower, whereas A. fabae preferred sunflower and M. persicae did not show any preference. In a field experiment, the growth rate of A. fabae on caged ragweed plants was similar to that in the greenhouse, but the final numbers of B. helichrysi and M. persicae after 30 days was ten and seven times lower than under greenhouse conditions, respectively. On exposed field plants, B. helichrysi was more abundant than other species. However, no aphid species affected the height or dry mass of either caged or exposed plants during a 30-day period. Under controlled conditions aphids effectively hampered development and pollen production of ragweed, however, under Hungarian field conditions the development of ragweed was much more dynamic, therefore no deleterious effect of aphid feeding occurred.

Hieracium-associated aphid parasitoid guilds (Hymenoptera: Braconidae: Aphidiinae) in Europe

Eleven aphidiine braconid species are associated with 10 aphid species to form over 50 tritrophic associations in Europe. The host aphids belong to five genera, Aphis L., Brachycaudus Van der Goot, Hyperomyzus Börner, Nasonovia Mordvilko, and Uroleucon Mordvilko, and feed on 11 Hieracium species. Five new host plant records are reported. The associated aphidiine guilds are linked with the taxonomic position of the host aphids. Host aphids such as Brachycaudus helichrysi (Kaltenbach) and Uroleucon spp. are broadly oligophagous, but Nasonovia spp., Aphis hieracii Schrank, and Hyperomyzus hieracii (Börner) are specific mainly to Hieracium and related plants. A key for the identification of aphidiine species associated with aphids on Hieracium plants in Europe is provided.

Aphids (Hemiptera: Aphidoidea) on cultivated and self-sown plants in Greece

The present work covers original information on aphids (Hemiptera: Aphidoidea) from Greece during 1995–2005. The individual aphid taxa were collected from their host plants and identified. The plant taxa were classified in two major categories: cultivated and self-sown. The cultivated ones were classified as: herbaceous, climbing and trees. The selfsown ones were classified as: annual herbaceous, annual or biennial herbaceous, biennial or perennial herbaceous, perennial herbaceous, shrubby and trees Two hundred twelve plant taxa were identified on which 105 aphid taxa were recorded. We report 391 plant taxa-aphid taxa associations from which, 190 are referred to cultivated and 201 to self-shown plant taxa. Aphis gossypii was found to infest the widest spectrum of cultivated plant taxa whereas Brachycaudus helichrysi was found to infest the widest spectrum of self-sown plant taxa. Myzus persicae was found to infest the widest spectrum of the total number of plant taxa. Information for several economically unimportant aphid taxa in the area are also presented.

Spatial and temporal distribution of winged aphids (Hemiptera: Aphididae) frequenting blueberry fields in southwestern British Columbia and implications for the spread of Blueberry scorch virus

AbstractAlate aphids were sampled in five fields of commercial blueberry, Vaccinium corymbosum L. (Ericaceae), during 2001 and 2002 using yellow tile, green tile, and Tremclad® yellow water traps. Eighty-seven species were identified among a total of 7722 alatae. Several of the species are known virus vectors, including Aphis fabae Scopoli, Brachycaudus helichrysi (Kaltenbach), Hyalopterus pruni (Geoffroy), Hyperomyzus lactucae (L.), Myzus persicae (Sulzer), Rhopalosiphoninus staphyleae (Koch), and Rhopalosiphum padi (L.). The number of species caught varied with year, and the number of species and the total number of alatae varied with field, trap colour, and season. More species were caught in 2001 than in 2002, in yellow than in green traps, and in the summer than in the spring or the autumn, and more alatae were caught in Tremclad® yellow traps than in yellow or green tile traps, and in the autumn than in the spring or the summer. However, numerous interactions limit generalizations. Analyses of the data for individual species revealed similar patterns and interactions. The effects of year, field, trap colour, and season varied with species. Given nonpersistent virus transmission and the large numbers of alatae caught of species that are known virus vectors, there is considerable potential for spread of Blueberry scorch virus by migrant aphids. Field- or area-specific and season-specific control strategies could be developed once the virus vector status of the different species is known. In addition, given the number of significant interactions observed in the data, there is a need to investigate alternative, generalized approaches to reducing virus transmission rates, such as applying whitewash or kaolin particle film to blueberry leaves.

Occurrence of Beet western yellows virus and its aphid vectors in over-summering broad-leafed weeds and volunteer crop plants in the grainbelt region of south-western Australia

During the summer periods of 2000, 2001, and 2002, presence of Beet western yellows virus (BWYV) was assessed in tests on samples from at least 12 broad-leafed weed species and 5 types of volunteer crop plants growing in the grainbelt region of south-western Australia. In 2000, BWYV was detected in 2 of 35 sites in 2% of 1437 samples, whereas in 2001 and 2002 the corresponding figures were 3 of 108 sites in 0.04% of 8782 samples, and 1 of 30 sites in 0.08% of 2524 samples, respectively. The sites with infection were in northern, central, and southern grainbelt districts, and in high and medium rainfall zones. The hosts in which BWYV was detected were the weeds Citrullus lanatus (Afghan or wild melon), Conzya spp. (fleabane), Navarretia squarrosa (stinkweed), and Solanum nigrum (blackberry nightshade), and the volunteer crop plant Brassica napus (canola). Small populations of aphids were found over-summering at 28% (2000), 4% (2001), and 17% (2002) of sites, mostly infesting volunteer canola and Raphanus raphanistrum (wild radish). They occurred in high, medium, and low rainfall zones, but were only found in central and southern grainbelt districts. The predominant aphid species found was Brevicoryne brassicae, with Acyrthosiphon pisum, Brachycaudus helichrysi, Hyperomyzus lactucae, Lipaphis erysimi, Myzus persicae, and Uroleucon sonchi present occasionally. The importance of these findings in relation to the epidemiology and control of BWYV in the grainbelt is discussed.

Activity of aphids associated with lettuce and broccoli in Spain and their efficiency as vectors of Lettuce mosaic virus

This research sought to identify the aphid virus vector species associated with lettuce and broccoli crops in Spain, and to determine their population dynamics and ability to transmit Lettuce mosaic virus (LMV). Green tile traps and Moericke yellow water-pan traps were used to monitor aphid flights during the spring and autumn growing seasons of 2001. Aphid species feeding on lettuce were counted weekly. The transmission efficiencies of LMV were determined for the aphid species caught most frequently. The Moericke traps generally caught more aphid species than the tile trap, but the latter was the most suitable to estimate flight activity of species involved in virus spread. Spring aphid catches indicated that the main aphid species landing on lettuce in the regions of Madrid and Murcia was Hyperomyzus lactucae, but Brachycaudus helichrysi was also abundant in both regions. In broccoli in the Navarra region, the most abundant species in spring were Aphis fabae, B. helichrysi and H. lactucae. In autumn-sown crops, the main species landing on lettuce in the Madrid region were Hyadaphis coriandri and Aphis spiraecola. In Murcia, A. spiraecola and Myzus persicae were the most abundant, while in Navarra, Therioaphis trifolii, and various Aphis spp. were the most numerous landing on broccoli. The main aphid species colonising lettuce was Nasonovia ribisnigri, but other less abundant colonising species were Aulacorthum solani and Macrosiphum euphorbiae. The most efficient vectors of LMV were M. persicae, Aphis gossypii and M. euphorbiae, while A. fabae and H. lactucae transmitted with low efficiency, and Rhopalosiphum padi and N. ribisnigri did not transmit. Occurrence of LMV epidemics in central Spain in relation to aphid flights and the role of weeds as virus reservoirs is discussed.

Delayed control of weeds in glyphosate-tolerant sugar beet and the consequences on aphid infestation and yield

An experiment was set up in 1998 to study the effect of glyphosate on the weeds and pests in glyphosate-tolerant sugar beet, in comparison with a conventional herbicide regime. Glyphosate at 1.08 kg ha−1 was first applied at the two- to four-leaf, 8- to 10-leaf and 12- to 14-leaf stage of the crop, followed by a second application at the same rate two to four weeks later. Weed growth did not affect sugar beet emergence or establishment, but, in untreated controls and the two later glyphosate treatments, weeds almost completely covered the ground, leading to reduction of root weight, sugar concentration and yield at harvest. The number of aphids (mostly Myzus persicae Sulzer) in the beet in June was significantly higher on plots treated with glyphosate at the two- to four-leaf stage than on untreated plots or plots treated later with glyphosate. Large numbers of the leaf curling plum aphid (Brachycaudus helichrysi Kaltenbach) colonised the weeds within untreated or later-treated plots. These were accompanied by predators and parasites which eventually caused substantial mortality in the aphid populations. There was evidence that glyphosate-treated weeds, although not in competition with the crop, were still able to provide sustenance for aphids. Very low levels of virus yellows were observed in the trial, and there were no significant differences between treatments. The results suggest that the latest application of the first glyphosate spray in a two-spray programme should be before the eight-leaf stage of the sugar beet to prevent weed competition reducing yield. Further studies on late control of weeds and insect diversity are being carried out. © 2000 Society of Chemical Industry

Newly Established and Rarely Collected Aphids (Homoptera: Aphididae) in Florida and the Southeastern United States

Several aphid species are reported as newly established in Florida and/or the southeastern United States, including Acyrthosiphon kondoi Shinji, Aphis amaranthi Holman, Brachycaudus helichrysi (Kaltenbach), Coloradoa achilleae Hille Ris Lambers, Hyadaphis coriandri (Das), Hyperomyzus carduellinus (Theobald), Melanaphis sp., Schizaphis rotundiventris (Signoret), Shivaphis celti Das, Takecallis arundicolens (Clarke), and Toxoptera citricida (Kirkaldy). Further establishment records are reported for Trichosiphonaphis polygoni (van der Goot) that was previously reported from a few counties in Florida and Georgia. Recent Florida finds are reported for three native species, including Aphis minima Tissot, Kaltenbachiella ulmifusa (Walsh & Riley), and Uroleucon elephantopicola Robinson. Identification information is provided for newly introduced exotic species.

Aphids (Homoptera: Aphididae) Colonizing Peach in the United States or with Potential for Introduction

Eleven aphid species known to colonize peaches in the United States and one species not known from the United States are described and illustrated. Aphis spiraecola Patch, Brachycaudus helichrysi (Kaltenbach), Brachycaudus persicae (Passerini), Brachycaudus schwartzi (Borner), Hyalopterus pruni (Geoffroy), Hysteroneura setariae (Thomas), Macrosiphum euphorbiae (Thomas), Myzus cerasi (F.), Myzus persicae (Sulzer), Myzus varians Davidson, Pterochloroides persicae (Cholodkovsky), and Rhopalosiphum nymphaeae (L.) are included in the present paper. A brief summary of taxonomic characters, usual hosts, and distribution within the United States are given for each species. Pictorial and dichotomous keys are included to aid personnel charged with detection, identification, and control of aphids associated with peaches in the United States.

Comparison of two methods, based on counts and damage symptoms, to assess population dynamics of the leaf‐curling plum aphid Brachycaudus helichrysi (Hom., Aphididae) on sunflower

Abstract: The population dynamics of Brachycaudus helichrysi on sunflower were described during 3 years using principal component analyses. The relationship between the dynamics of aphid numbers and the dynamics of the intensity of the leaf‐curling symptom, described with a scale from 1 to 5, is discussed. For a given year and cultivar, there was good concordance between the two dynamics. Four sunflower cultivars were compared in the same natural conditions. There were differences between cultivars with respect to their aphid infestations and the expression of the leaf‐curling symptoms. Pest management can often be simplified by basing it only on the survey of leaf‐curling symptoms.

Pre-penetration events affecting host specificity of Verticillium lecanii

The pathogenicity of two isolates of Verticillium lecanii towards non-target invertebrates and six species of aphid was tested in bioassays. There was no evidence of infection in any of the 20 non-target invertebrates. All target aphid species were susceptible to at least one isolate. The level of susceptibility varied between aphid species, with Myzus persicae and Brachycaudus helichrysi showing the greatest susceptibility. Studies on initial spore deposition, retention and germination on two susceptible aphid species and four resistant non-target insects revealed differences in the behaviour of the pathogen between the two groups. Spore density mm-2 was greater on susceptible insects both immediately post-inoculation and following 24 h incubation. There was no loss of spores from M. persicae over 24 h. All other species showed more than 50% spore loss in the same period. However, even after 90% spore loss, large numbers of spores remained on the bigger insects such as Agonum dorsale. Germination and germ-tube growth were possible on such resistant non-target insects, indicating that resistance to infection occurs after this stage. There was little difference in rate of germination on the two groups. However, differences in germ-tube growth were evident, with the production of longer and narrower germ-tubes on the resistant insects.

Sequential Sampling of Brachycaudus helichrysi (Homoptera: Aphididae) in Sunflower Fields

A sequential sampling plan for the leaf-curling plum aphid, Brachycaudus helichrysi Kaltenbach, on sunflower was developed using the fixed-precision method of Green. Our sequential sampling plan was validated using a resampling simulation approach with 5 independent data sets ranging in density from 5.8 to 188.2 aphids per sample unit. Sampling plans with a relative precision level of 0.30 were not recommended because of the low sample number and high variation that invalidated the normality assumption. Simulated results did not agree with the desired precision level for only 1 data set. This data set also deviated from our Taylor power law model. For the other data sets, simulated precision levels were generally better than the desired fixed levels. Variability of the B. helichrysi sequential sampling criteria was high for mean estimates and for the levels of precision.

Painted Containers: A New Method for Imidacloprid Application

The effectiveness of two methods of application of the insecticide imidacloprid in controlling 1) aphids (Brachycaudus helichrysi) on Chrysanthemum plants, Dendranthema ×grandiflora (Ramat) (cv. Nob Hill) and 2) whitefly (Bemisia argentifolii) on poinsettia, Euphorbia pulcherrima (Wild.) (cv. Freedom Red) were compared. Plants were grown in containers with their interior covered by a mixture of flat latex paint and several concentrations of imidacloprid (0, 10, 21, 42, and 88 mg·L–1), or treated with a granular application of the insecticide (1% a.i.) according to label recommendations. All imidacloprid treatments were effective in reducing aphid survival after 8 weeks. The two most effective treatments were: granular (1% a.i.) and 88 mg·L–1 with an average of 0.2 aphid per plant as opposed to 50.4 aphids per plant for the control. The 42-mg·L–1 treatment had an aphid survival rate 1.6 aphids per plant. All imidacloprid treatments were effective in reducing white fly larvae. The 42 and 88 mg·L–1 and the granular (1% a.i.) were equally effective in reducing larvae numbers in lower poinsettia leaves: 0.5, 1.9, 0.9 larvae/2.5 cm leaf disk, respectively, while the control treatment had 62.9. None of the plants given treatments with paint showed any sign of phytotoxicity. These results suggest the possibility of a new application method for systemic chemicals with the potential of reducing or eliminating Worker Protection Standard (WPS) Restricted Entry Intervals (REI) and reducing the release of chemicals to the environment. Chemical name used: 1-[(6-Chloro-3-pyrimidil)]-N-nitro-2-imidazolidinimine.

Influence of the leaf curling plum aphid (Brachycaudus helichrysi) on stem diameter, seed yield, and their relationship, in sunflower

SUMMARYThe leaf-curling plum aphid (Brachycaudus helichrysi Kalt.) is one of the main pests of sunflower (Helianthus annuus L.) in Europe. Yield losses were assessed in open field conditions and natural infestations over a 3-year period in Central West France. Plant variability and the choice of the more vigorous plants by aphids in open field conditions were two factors interfering with the experiments. To improve their sensitivity and to correct for biases without expanding the experimental design, an analysis of covariance was the best compromise. Field and cage experiments were conducted between 1985 and 1989 to assess the influence of aphids on the relationship between stem diameter at harvest and seed yield. As an indicator of plant vigour (size and yield), stem diameter at harvest was the best choice, as neither its relationship with seed yield nor its mean value was affected by aphid infestation. It was then used as a covariate to study yield losses. Aphid populations were quantified weekly from the beginning to the end of the infestations according to the leaf-curling symptom and to the number of aphids per plant. Multivariate analyses followed by cluster analysis identified groups of plants displaying similar infestation dynamics. It was found that when aphid populations reached > 100 per plant at the budding stage, yield losses occurred. When populations were < 100 aphids per plant at the budding stage and then decreased, no yield loss was observed. This gives growers ample time to monitor populations and treat crops.

Effects of temperature on aphid phenology

AbstractDaily samples between 1964 and 1991 from suction traps throughout Great Britain were used to study the migration phenologies of five aphid species: Brachycaudus helichrysi, Elatobium abietinum, Metopolophium dirhodum, Myzus persicae and Sitobion avenae, and their relationship with temperature. Regression relationships have been established between characteristics of aphid phenology and temperature, latitude and longitude for each species. There were differences between species in the period for which temperature was most strongly associated with aphid phenology. The study indicates that temperature, especially winter temperature, is the dominant factor affecting aphid phenology, for all five species. A 1 °C increase in average winter temperature advanced the migration phenology by 4–19 days depending on species. Effects of temperature on the aphid phenology are similar between holocyclic and anholocyclic species, unlike the effects of temperature on date of first flight record which have been previously shown to be important only in anholocyclic species.