Showing papers on "Myzus persicae published in 1973"
TL;DR: The factors responsible for determining the host-plants and feeding sites of aphids, and the various probing activities (the role of the labium, stylet insertion, surface saliva deposition, the behaviour of the aphid, virus transmission) are examined.
Abstract: The factors responsible for determining the host-plants and feeding sites of aphids, and the various probing activities (the role of the labium, stylet insertion, surface saliva deposition, the behaviour of the aphid, virus transmission) are examined. There is a brief review of stylet structure and movement and the possible sensory nature of these organs, followed by a detailed review of the characteristics of aphid stylet paths in plant tissues. The penetration of epidermis and vascular tissues is treated separately while that within the intermediate tissues is covered in relation to leaves and stems, roots, trees, galls and excised tissue as well as in separate sections on Aphis fabaeScopoli and Myzus persicae (Sulzer). Stylet destinations and behaviour in the sieve tubes are discussed together with general features such as rate and depth of penetration, guidance to the feeding site, effects of tissue hardness and stylet withdrawal. The ingestion rate of plant sap is reviewed and its constitution and importance examined together with the significance of artificial diets. The salivary secretions including sheaths and tracks, their functions and their role in the transference of material between aphid and host are dealt with. The nature of the physical and internal damage resulting from aphid feeding is briefly covered, and also some plant-insect interrelations. The aphid species whose stylets have been examined in plant tissue are listed.
327 citations
TL;DR: The chemical structure of the repellent odour found in the cornicle secretion of the aphid M. persicae1 has been identified as trans-β-farnesene.
Abstract: THE chemical structure of the repellent odour found in the cornicle secretion of the aphid M. persicae1 has been identified as trans-β-farnesene.
143 citations
TL;DR: A virus, designated as beet necrotic yellow vein virus (BNYVV), was isolated from sugar beet plants affected with rizomania disease and did not serologically relate to soil-borne wheat mosaic virus, tobacco rattle virus, and tobacco mosaic virus.
Abstract: A virus, designated as beet necrotic yellow vein virus (BNYVV), was isolated from sugar beet plants affected with rizomania disease The virus was transmitted through the soil and by sap inoculation, but not by the aphids, Myzus persicae and Aulacorthum solani Of 84 species of plants belonging to 16 families inoculated by sap, 15 of 17 species belonging to Chenopodiaceae, Tetragonia expansa and Gomphrena glohosa plants became infected with the virus The virus tended to be restricted to the inoculated leaves of all host plants, but sugar beet, spinach, and Beta macrocarpa plants occasionally became infected systemically The thermal inactivation point of the virus was between 65 and 70C, the dilution end point was 10-4, and the infectivity was retained for 5 days at 20C or for 8 days at 4C BNYVV particles (isolate YS) had a diameter of about 20nm and three peaks of length distribution at 95-110nm, 255-270nm, and 370-390nm The virus was partially purified by organic-solvent clarification and polyethylene glycol precipitation An antiserum to BNYVV had a titer of 1/1, 024 in ring precipitin tests In agar gel-diffusion tests, a band of precipitation was produced between the virus and its antiserum BNYVV did not serologically relate to soil-borne wheat mosaic virus, tobacco rattle virus, and tobacco mosaic virus The present cryptogram of BNYVV is */*:*/*:E/E:S/(Fu)
131 citations
TL;DR: Evidence for regurgitation, along with previous reports indicating that aphids test feed in plant epidermal cells during superficial probes, is interpreted as supporting a hypothesis of virus transmission by Regurgitation.
Abstract: A detailed account of the membrane-feeding behavior of Myzus persicae (Sulzer) is presented. Aphids can regurgitate ingested material during feeding activity. During regurgitation, the flow of material and the pulsing of the sucking pump are as regular as during ingestion, which indicates that the pump can function in either direction. Evidence for regurgitation, along with previous reports indicating that aphids test feed in plant epidermal cells during superficial probes, is interpreted as supporting a hypothesis of virus transmission by regurgitation. It is postulated that aphids acquire virus by ingestion, carry it internally in the alimentary canal, and inoculate it into plants by regurgitation.
41 citations
TL;DR: To determine their importance as virus vectors, 1419 alate aphids were collected, mainly from field plots of garden peas in spring 1966, 1967, and 1968, and the viruses detected and their vectors were Subterranean clover red leaf virus (SCRLV), which caused the leaves of the test plant to be small and turn red as they matured.
Abstract: To determine their importance as virus vectors, 1419 alate aphids were collected, mainly from field plots of garden peas (Pisum sativum L. var. sativum L.) in spring 1966, 1967, and 1968; 55% were Aulacorthum solani (Kltb.), 25% Myzus persicae (Sulz.), 16% Macrosiphum euphorbiae (Thos.), and 3% Aphis craccivora Koch. Alatae of each species were transferred either singly or in groups to subterranean clover (Trifolium subterraneum cv. Bacchus Marsh) test plants. The viruses detected and their vectors were: a. Subterranean clover red leaf virus (SCRLV), which caused the leaves of the test plant to be small and turn red as they matured. Alatae of A. solani often infected plants with SCRLV, and alatae of M. euphorbiae did so occasionally. In glasshouse tests SCRLV was transmitted circulatively by apterae of A. solani but not by apterae of M. persicae or A. craccivora, although M. persicae appeared to transmit SCRLV when PELRV was also present. b. Pea leaf roll virus (PELRV), which caused marked stunti...
37 citations
TL;DR: All applications of systemic insecticides in combination with multiple applications of foliar spray gave significant control of aphids, and most treatments significantly suppressed the spread of disease.
Abstract: Systemic insecticides were applied to the soil on each side of potato seed pieces at planting time and/or were sidedressed into the soil when 75% of the plants emerged, and multiple foliar sprays were applied to obtain seasonal control of Myzus persicae (Sulzer) and the suppression of potato leaf roll virus on ‘Russet Burbank’ potatoes in eastern Washington. Aldicarb gave superior control of aphids and suppressed spread of the virus; disulfoton gave fair control of aphids, but not much suppression of potato leaf roll virus; and phorate did not give sufficient control of aphids or the disease. The 2 applications of the systemic insecticides were more effective than either single application. Endosulfan and oxydemetonmethyl as foliar sprays (2-5 applications) gave better control of aphids than demeton and disulfoton but none significantly suppressed spread of the virus. All applications of systemic insecticides in combination with multiple applications of foliar spray gave significant control of aphids, and most treatments significantly suppressed the spread of disease.
23 citations
TL;DR: The effects of former hosts on the ability of M. persicae to colonise plants may be important both in work on resistance to aphids and in the epidemiology of aphid-borne diseases.
Abstract: Apterous adult Myzus persicae (Sulz.) of a glasshouse strain differed greatly in their ability to colonise sugar-beet according to the plant on which they and their forebears were cultured. Those from Chinese cabbage (Brassica pekinensis) settled least readily on beet, whilst aphids from broad beans (Vicia faba) produced larger populations than those cultured on sugar-beet. When reared wholly on groundsel (Senecio vulgaris) young adults differed in their ability to colonise Chinese cabbage, sugar-beet and broad bean according to their parents' culture host species, and these differences were detected in a second generation reared wholly on groundsel. The responses of clones isolated from cultures maintained continuously on Chinese cabbage and broad bean were similar, showing that the effect was caused by the aphids' host-plant experience, and was not due to fixed, heritable characters of the sub-cultures. Some, but not all clones of M. persicae collected from the field showed enhanced colonising ability after culture on broad bean as compared with Chinese cabbage. This was apparent on sugar-beet and lettuce (Lactuca sativa). These effects of former hosts on the ability of M. persicae to colonise plants may be important both in work on resistance to aphids and in the epidemiology of aphid-borne diseases.
22 citations
TL;DR: Polyacrylamide gel electrophoresis was used to demonstrate six esterases, hydrolysing 1-naphthyl acetate, in both strains of Myzus persicae, and significant differences were evident in the activities and mobilities of E 3 and E 4 bands.
Abstract: 1. 1. Polyacrylamide gel electrophoresis was used to demonstrate six esterases, hydrolysing 1-naphthyl acetate, in both strains of Myzus persicae . 2. 2. The esterases were classified as cholinesterases, carboxylesterases or arylesterases depending upon their reactions with eserine sulphate and dichlorvos. 3. 3. Considerable differences were evident in the activities and mobilities of E 3 and E 4 bands (both identified as carboxylesterases) between the two strains. 4. 4. Similar differences were not observed in the phosphatases of the two strains when sodium 1-naphthyl phosphate was used as substrate.
21 citations
TL;DR: Following 10 days of infestation by the aphid Myzus persicae, there was an increase in the amount of growth inhibiting substances and a decrease in cytokinins, gibberellins and auxins in infested seedlings as compared with similar uninfested radish seedlings.
Abstract: SUMMARY
Following 10 days of infestation by the aphid Myzus persicae there was an increase in the amount of growth inhibiting substances and a decrease in cytokinins, gibberellins and auxins in infested as compared with similar uninfested radish seedlings. Even after previously infested seedlings have been freed of aphids for 10 days, differences in the hormone balance remained. The possible relationships between the changes in hormonal balance and the effect of the aphid infestation on growth, translocation and wilting are discussed.
18 citations
TL;DR: A virus obtained from pelargonium cvs Irene and Paul Crampel appears to differ from any previously reported; although symptomless in most pelargonia cvs tested, it caused colour break in the flowers of two seedling clones, and the name pelargonial flower-break virus is proposed.
Abstract: SUMMARY
A virus obtained from pelargonium cvs Irene and Paul Crampel appears to differ from any previously reported; although symptomless in most pelargonium cvs tested, it caused colour break in the flowers of two seedling clones. It seems uncommon in pelargoniums. The virus was readily transmitted by inoculation of sap, but not by Myzus persicae with short feeds, by dodder or through seed. It infected only fifteen of 100 species tested in six of thirty-five plant families. Pelargoniums were freed from the virus by heat-treatment.
The virus remained infective after 10 min at 85 oC, 3 wk at 20 oC or 27 wk at 2 oC; it was infective at 1/500000 dilution of Nicotiana clevelandii or Chenopodium quinoa sap.
Purified preparations were readily made by several methods, and contained isometric particles c. 30 nm diameter. Although a good antigen, the virus was serologically unrelated to any of forty-two isometric viruses. In immunoelectrophoresis, the virus moved as a single antigenic component towards the cathode. It gave a single, specific zone in density-gradient centrifugation, and one moving component (s020 w= 125 S) in analytical centrifugation. The virus contained one protein of mol. wt. c. 41000. The present cryptogram of the virus is (R)/*: */*:S/S:S/*, and the name pelargonium flower-break virus is proposed.
17 citations
TL;DR: Results show that alpha naphthyl acetate-hydrolysing esterases were considerably more active in the R (K m = 1·25 × 10 −4 M ) than in the S strain, and carboxylesterase activity showed greater recovery after inhibition.
Abstract: 1. 1. A colorimetric investigation was conducted to study the kinetics of esterases hydrolysing 1- and 2-naphthyl acetates and butyrates, of an OP-susceptible and an OP-resistant strain of Myzus persicae. 2. 2. Results show that alpha naphthyl acetate-hydrolysing esterases were considerably more active in the R ( K m = 1·25 × 10 −4 M ) than in the S strain ( K m = 3·15 × 10 −4 M ). 3. 3. R strain carboxylesterases were not only more resistant to in vitro inhibition with eserine and dichlorvos but also showed greater recovery after inhibition. 4. 4. Loss of OP-resistance in Myzus reared in an insecticide-free environment was accompanied by a corresponding drop in carboxylesterase activity.
TL;DR: A 2-year study of the spring population of Myzus persicae (Sulzer) on peach trees showed that the number of surviving fundatrices reaching reproductive maturity represented less than 2% of the overwintering eggs.
Abstract: A 2-year study of the spring population of Myzus persicae (Sulzer) on peach trees showed that the number of surviving fundatrices reaching reproductive maturity represented less than 2% of the overwintering eggs. Colonies established from surviving fundatrices protected from natural enemies by slecve cages displayed a tremendous numerical recovery. For example, in a protected environment (cage) the average number of alate aphids per stem mother was 3596 in 1970, and 1080 in 1971. In contrast, on unprotected twigs the natural enemies, primarily coccinellid and syrphid predators, played a major role in reducing the production of alate aphids by an estimated 95% in both years (based on counts of immature aphids).
TL;DR: The introduction of flightless coccinellids to promote a rapid increase in the population appears practical and might be used as a biotic control agent on vegetable crops if a practical means of inhibiting flight could be developed.
Abstract: The impact of aphidophagous predators on populations of Myzus persicae (Sulzer) on field-grown sugarbeets was investigated by periodically removing the predators present in control plots and adding selected predators (elytra glued to reduce dispersion) to the predator complex present in other plots. At the time when aphids were most numerous in the control plots, the plots treated with releases of geocorids + nabids or chrysopids only had significantly fewer (1/3) aphids. However, the fewest aphids were found in plots in which flightless coccinellids only had been released. In addition, these plots had substantially more coccinellid eggs and larvae, though the control plots had 4 times as many aphids per plant. The introduction of flightless coccinellids to promote a rapid increase in the population therefore appears practical. Also, coccinellids might be used as a biotic control agent on vegetable crops if a practical means of inhibiting flight could be developed.
TL;DR: Results support hypothesis that excision enhances senescence and the associated increase in soluble N suggests quantitative and/or qualitative improvement in phloem sap which favors aphid growth.
Abstract: Apterous Chaetosiphon Fragaefolii (Cockerell) reared on excised discs from mature leaves of Fragaria vesca (L.) were larger and produced more alate offspring than aphids reared on intact leaves. Intact leaves contained 3.8 nig soluble N/g, compared with five-day-old excised tissue which contained 6.0 mg soluble N/g dried tissue. Aphids reared on discs floated on N6Benzyladenine were smaller and produced fewer alate offspring than those reared on discs floated on water. Discs receiving 10 ppm of the cytokinin contained 2.7 mg soluble N/g after five days. Forty ppm of N6B added to the artificial diet of Myzus persicae (Sulzer) had no effect on growth or uptake. Results support hypothesis that excision enhances senescence. The associated increase in soluble N suggests quantitative and/or qualitative improvement in phloem sap which favors aphid growth. Cytokinin (N6B) inhibited senescence and opposite effect occurred. Discs treated with N6B produced deterrent effect on large teneral adults but not on smaller adults of random age.
TL;DR: Insect developmental inhibitors applied to colonies of the green peach aphid, Myzus persicae (Sulzer), on peach trees in early May reduced the production of winged migrants as much as 75% and delayed migration for as long as 15 days, but these compounds affected mainly the alatoid nymphs and not the reproductive adults; therefore, apterous aphids would be available as prey to the natural enemies that are present on Peach trees in the spring.
Abstract: Insect developmental inhibitors applied to colonies of the green peach aphid, Myzus persicae (Sulzer), on peach trees in early May reduced the production of winged migrants as much as 75% and delayed migration for as long as 15 days. However, these compounds affected mainly the alatoid nymphs and not the reproductive adults; therefore, apterous aphids would be available as prey to the natural enemies that are present on peach trees in the spring. A reduction in the number of aphid migrants and a delay in their migration from peach trees would result in a subsequent reduction in the number of aphids produced on diseased secondary hosts and a delay in the migration of these aphids to host crops. In most cases, this would result in an increase in yield and an economic gain to the growers.
TL;DR: Symptoms associated with aphid infestation cannot be attributed either to virus disease or initially to exhaustion of the seedling's carbohydrate and nitrogen reserves.
Abstract: SUMMARY
After 10 days of infestation by the aphid Myzus persicae growth of radish seedlings was reduced by 38 %, and the volume of sap bleeding from the stumps of cut stems of infested seedlings was 4% of that exuding from the stumps of uninfested seedlings of the same age. Diminished bleeding could not be accounted for by the 52 % reduction in the weight of the roots of infested seedlings. After 14 days of infestation, necrotic patches developed along the veins of the cotyledons which yellowed noticeably. If freed of aphids the seedlings subsequently resumed growth and their was an increase in the volume of bleeding sap produced by their cut stems. Symptoms associated with aphid infestation cannot be attributed either to virus disease or initially to exhaustion of the seedling's carbohydrate and nitrogen reserves. Possible causes of the symptoms described are discussed.
TL;DR: Investigation of the transmission and retention of inoculativity of potato leaf-roll virus (PLRV) in the green peach aphid, Myzus persicae (Sulz.), finds that virus recovery from viruliferous aphid extracts was influenced by the length of the acquisition feeding period of the aphids used as sources of inoculum.
Abstract: This paper reports the results of further investigations of the transmission and retention of inoculativity of potato leaf-roll virus (PLRV) in the green peach aphid, Myzus persicae (Sulz.).The frequency of virus transmission, the length of the latent period, and the retention period of inoculativity of the virus in the injected aphids were dependen ton the virus concentration of inocula. Virus recovery from viruliferous aphid extracts was influenced by the length of the acquisition feeding period of the aphids used as sources of inoculum. However, irrespective of the length of the acquisition feeding period, the virus concentration in the aphids tended gradually to decrease after leaving the source plant. The virus was recovered from the guts and blood, but not from the salivary glands of aphids given a 4-day acquisition feeding period on infected plants. Virus recovery from the aphid blood was also dependent on the length of the acquisition feeding period of aphids used as sources of inoculum. PLRV was detected in the blood of aphids up to 2 days after injection with a massive dose of the virus solution using aphid extracts as the inoculum. The results of virus recovery with the blood of the injected aphids were the same as for those following an acquisition feeding period. Attempts to maintain the virus inoculativity in serial passage using extracts or blood of viruliferous aphids were unsuccessful.
TL;DR: Dichlorvos was more potent than TOCP as an inhibitor of CarEs and was equally effective against CarEs of both strains, but ethyl-butyrate-splitting carboxylesterases were less active in the R-strain.
Journal Article•
TL;DR: Sap inoculation studies showed that except for Cassia occidentalis, which was not susceptible to PFMV-MU, the host range for the trvo virus isolates were similar, however, there was a slight variation in symptoms expressed on the same indicator plant separately inoculated with the two virus isolate.
Abstract: Two new virus isolates, passion fruit mosaic virus - Jalan Kebun (PFMV-K) and passion fruit mosaic virus - University of Malaya (PFMV-MU) were obtained from Passiflora laurifolia and P. edulis f.flavicarpa respectively. Sap inoculation studies showed that except for Cassia occidentalis, which was not susceptible to PFMV-MU, the host range for the trvo virus isolates were similar. However, there was a slight variation in symptoms expressed on the same indicator plant separately inoculated with the two virus isolates. The following plants were found to be susceptible to both the virus isolates: Chenopodium arnaratilicolor, Gomphrena globosa, P. edulis, P. edulis f.flavicarpa, P. maliformis, P. foetida, P. lingularis, P. mocrocorpa, P. mollisima, P. platyloba, and P. vitifolia. Plants which were found not susceptible when inoculated with the 2 virus isolates included: Cucumis sativus. Lathyrus odoratus, Phoseolus vulgaris, Vicia faba, Vigna sesquipedalis, V. sinensis, Plantago major, Capsicum annuum, Datura stramonium, Nicotiana glutinosa, N. tabacum, N. rustica, and N. xanthi. The thermal inactivation point for PFMV-K was between 67°C to 69°C and that for PFMV-MU at 69°C to 70°C. Dilution-end-point of the two virus isolates were between 10-1 to 1O-2. PFMV-K remained infective for 2 days at 25°C while PFMV-MU remained infective for 6 days at 25°C. Apart from C. occidentalis, which could be used as a differential host for the 2 virus isolates, aphid vectors of the two viruses could also be used to differentiate between them. Myzus persicae (Sulz.) readily transmitted PFMV-K and PFMV-MU in a nonpersistent manner while Aphis craccivora Koch. and A. gossypii Glover. transmitted PFMV-MU non-persistently, but failed to transmit PFMV-K. Rhopalosiphum maidis Fitch and Toxoptera citricidus Kirk were not vectors of both virus isolates. Both PFMV-K and PFMV-MU were readily graft transmissible using the leaf-graft technique. Transmission tests with leaf-exudate of both virus isolates gave negative results. PFMV-K and PFMV-MU could be spread from diseased to healthy passion fruit vines during pruning operations.
Dua penyakit vairus baharu, vairus mosaik buah susu - Jalan Kebun (PFMV-K) dan vairus mosaik buah susu - Universiti Malaya (PFMV-MU) terdapat dari Passiflora laurifolia dan P. edulis f.flavicarpa masing-masrng. Suntikan cecair (sap inoculation) menunjukkan bahawa host range untuk kedua-dua vairus tersebut adalah sama kecuali Cassia occidentalis yang dapat menahan PFMV-MU. Pokok-pokok penunjuk menunjukkan tanda-tanda yang berbeza bila disuntik dengan PFMV-K dan PFMV-MU masing-masing. Pokok-pokok yang dijangkiti oleh kedua-dua vairus itu ialah Chenopodium arnaratilicolor, Gomphrena globosa, P. edulis, P. edulis f.flavicarpa, P. maliformis, P. foetida, P. lingularis, P. mocrocorpa, P. mollisima, P. platyloba, and P. vitifolia. Pokok-pokok yang dapat menahan jangkitan kedua-dua vairus itu ialah Cucumis sativus. Lathyrus odoratus, Phoseolus vulgaris, Vicia faba, Vigna sesquipedalis, V. sinensis, Plantago major, Capsicum annuum, Datura stramonium, Nicotiana glutinosa, N. tabacum, N. rustica, and N. xanthi. Takad suhu haba tak cergas (thermal inactivation point) unruk PFMV-K adalah di antara 67°C dan 69°C C. dan untuk: PFMV-MU di antara 69°C dan 70°C. Takad kecairan (dilution-end-point) bagi kedua-dua vairus ialah di antara l0-1 dan 10-2. Pada 25°C, kuasa jangkitan PFMV-K masih ada selepas dua hari dan PFMV-MU pula selepas enam hari. Selain daripada C. occidentalis, pembawa kutu daun pun boleh juga diguna untuk membezakan dua vairus tersebut. Myzus persicae (Sulz.) membawa PFMV-K dan PFMV-MU secara tidak selalu manakala Aphis craccivora Koch. and A. gossypii Glover, membawa PFMV-MU secara tidak selalu tetapi gagal membawa PFMV-K. Rhopalosiphum maidis Fitch dan Toxoptera citricidus Kirk tidak boleh membawa vairus-vairus tersebut. PFMV-K dan PFMV-MU boleh dijangkitkan dengan cara cantuman. Pemindahan dengan mcnggunakan cecair daun (leaf exudate) dari pokok buah susu yang berpenyakit memberi keputusan yang negatif. PFMV-K dan PFMV-MU boleh dijangkitkan melalui penurasan.
TL;DR: Four experiments were conducted to compare some of the never chemicals for control of Myzus persicae (Sulzer) on cabage and spinach in south Texas and oxy-demetonmethyl showed the most promise as control agents.
Abstract: Four experiments were conducted during (1971–72 to compare some of the never chemicals for control of Myzus persicae (Sulzer) on cabage and spinach in south Texas. Acephate, Monitor® ( O, S -dinmethyl phosphoramidothioate), chlordimeform, Pirimor® 2-(dimethylamino) 5,6-dimethyl 4-pyrimidinyl dimethylcarbamate), and oxy-demetonmethyl showed the most promise as control agents. No visible phytotoxicity caused by any treatment was detected.
TL;DR: In 2 years, during the initial invasion of peach leaves by the green peach aphid,Myzus persicae (Sulzer), the number of gynoparae was low, and the distribution on leaves was random, but as the mean number increased, the distribution became intermediate and could not be distinguished from either a Poisson or a negative binomial.
Abstract: In 2 years, during the initial invasion of peach leaves by the green peach aphid,Myzus persicae (Sulzer), the number of gynoparae was low, and the distribution on leaves was random. Then as the mean number increased, the distribution became intermediate and could not be distinguished from either a Poisson or a negative binomial. Finally, as the mean continued to increase, the variance increased rapidly, and the population was found to fit a negative binomial distribution. Thus the aggregation response was verified because the dispersion pattern fitted a contagious distribution. A sampling plan was devised by which the dispersion parameterk was used to estimate the density of aphids per leaf based on the percentage of leaves infested. Sampling the third year of the study confirmed the validity of the sampling parameter that had been calculated from data for the 2 previous years.
TL;DR: The kinetics of dihydrofolate reductase activity were determined in a post-mitochondrial supernatant of whole aphid homogenate and the properties of the aphid enzyme are compared to those of di hydrofolates from other sources.
TL;DR: Dichlorvos and sulfotepp, as 10% aerosols, were effective in green house tests against Myzus persicae (Sulzer) and A phis fabae Scopoli on chrysanthemum plants.
Abstract: Dichlorvos and sulfotepp, as 10% aerosols, were effective in green house tests against Myzus persicae (Sulzer) and A phis fabae Scopoli on chrysanthemum plants However, dicholorvos was less effective with the susceptible cultivar ‘Mefo’ than with the more resistant cultivar ‘Good News’ because of the difference in the structure of the aphid population on the two cultivars The 2 insecticides penetrated equally well into blocks of plants