Chaetosiphon Fragaefolii Research Articles

Virus diseases of berry plants in Finland

Virus diseases of berry plants became more common and harmful in the 1960s, when berry cultivation expanded in Finland. Virus diseases seldom occur in strawberry because the main vector, Chaetosiphon fragaefolii, does not thrive in Finland. However NEPO-viruses are found in Finland in plant nurseries and in berry cultivations, and they may become a danger for strawberry as well as for raspberry growing. Both wild and cultivated raspberries are commonly infected by viruses. The vector aphids also occur in Finland. Reversion disease infects black currants. The veinbanding virus disease is common in red currants and gooseberries. Virus diseases of berries are poorely investigated in Finland. The healthy plant propagation and certification scheme was established in the 1970s. More research is needed in order to understand our virus problems, to develop proper test methods, and to prevent virus spread.

The strawberry aphid complex, Chaetosiphon (Pentatrichopus) spp. (Hemiptera: Aphididae): taxonomic significance of variations in karyotype, chaetotaxy and morphology

AbstractHolocyclic populations of aphids of the Chaetosiphon (Pentatrichopus) fragaefolii (Cockerell) group from Fragaria in British Columbia were found to have a homozygous 2n = 12 female karyotype, whereas samples from predominantly anholocyclic populations in Oregon, California, England and New Zealand have 13, 14, 15 or 17 chromosomes showing various degrees of structural heterozygosity. The 17-chromosome form is a morphologically recognizable taxon, C. jacobi Hille Ris Lambers. The other karyotypes apparently represent a series of parthenogenetic lineages derived from the 2n = 12 holocyclic form and carrying one, two or three autosome dissociations. The North American populations showed no correlation between karyotype and the number of submarginal setae, a character previously used in attempts to differentiate taxa within this species complex in western North America. Submarginal setal number varied greatly within and between clones and tended to increase in successive generations from the fundatrix, confirming that this character varies both genetically and seasonally and has little taxonomic value. Populations of the fragaefolii group from Rosa spp. in North America have a shorter rostrum than those from Fragaria. The name C. thomasi Hille Ris Lambers is assigned to this rose-feeding species, which is holocyclic on R. rugosa in British Columbia and colonizes Potentilla spp. (but apparently not P. anserina) as alternative hosts. Old World populations on Fragaria, presumably originating from North America, have longer siphunculi than North American populations of fragaefolii and few or no submarginal setae; these differences are probably due to founder effects. Both Old and New World populations of fragaefolii use P. anserina as an alternative host-plant.

Purification, characterization and serology of strawberry pseudo mild yellow edge virus.

Strawberry pseudo mild yellow edge virus (SPMYEV) was detected from strawberry cv. Hoko-wase. SPMYEV was readily transmitted from infected plants by the aphids, Chaetosiphon fragaefolii and Aphis gossypii to Fragaria species, but not by inoculation of sap. Filamentous virus particles were consistently observed in dip preparations and ultrathin sections of SPMYEV infected leaves, but not in healthy control leaves. They were therefore thought to be the particles of SPMYEV. The virus was successfully purified from infected Alpine strawberry by differential centrifugation in sucrose cushion, followed by sucrose density gradient centrifugation and CsC1 equilibrium density gradient centrifugation. The purified preparations contained filamentous particles 625nm in length and 12nm in width, and showed a typical UV spectrum of a nucleoprotein with max. and min. absorption at 260nm and 246nm, respectively. The A260/A280 ratio was 1.19. The bouyant density of purified virus in CsCl was 1.32g/cm3. The virus had a single stranded RNA with the mol. wt. of 2.5×106 daltons and one coat protein with the mol. wt. of 33, 500 daltons. The virus was serologically related to carnation latent virus. From these results, it is concluded that SPMYEV is a new member of the carlavirus group.

Purification, Properties and Serology of Strawberry Mild Yellow‐Edge Virus

AbstractOregon isolate My‐18 of strawberry mild yellow‐edge virus (SMYEV) was purified by comminution in liquid nitrogen, extraction in 0.1 M phosphate, 0.01 M DIECA, 1 % thioglycollic acid (pH 7.0) and differential and rate‐zonal density gradient (dg) centrifugation. The resulting ultraviolet‐absorbing dg band (A254 nm), not seen in healthy control preparations, contained isometric, 23 mm‐diameter, virus‐like particles. The partially purified MY‐18 virus was not transmitted to Fragaria vesca by means of membrane‐fed or injected Chaetosiphon fragaefolii. MY‐18 has an in vivo thermal inactivation point between 45 and 50 °C as determined by feeding C. fragaefolii on detached leaves that had been immersed in water for 10 min at various temperatures. In ELISA, rabbit antisera against MY‐18 differentiated between partially purified preparations from root and leaf tissue and between crude root but not crude leaf extracts from healthy and MY‐18‐infected Fragaria. Our data support the generally held hypothesis that SMYEV is a luteovirus. However, comparative ISEM and ELISA tests failed to reveal any serological releationship between MY‐18 and potato leafroll, beet western yellows, legume yellows, pea leafroll, or tobacco necrotic dwarf viruses.

Resistance of Fragaria chiloensis Clones to the Twospotted Spider Mite

Abstract Thirty clones of the beach strawberry, Fragaria chiloensis (L.) Duch., that were known to be resistant to strawberry aphid, Chaetosiphon fragaefolii (Cockerell), were evaluated for resistance to twospotted spider mite, Tetranychus urticae Koch. AH clones had fewer mites per leaf than the cultivar ‘Totem’. Two clones, BSP-14 and LCM-19, had totals of only 6 and 82 mites, respectively, on 4 dates compared to 1741 mites on ‘Totem’. The ‘Del Norte’ clone of F. chiloensis, previously used as a source of aphid resistance in breeding, was more susceptible than BSP-14 and LCM-19 to the mite.

PREDICTING THE TIME OF HATCH OF THE STRAWBERRY APHID, CHAETOSIPHON FRAGAEFOLII (HOMOPTERA: APHIDIDAE)

AbstractThe rate of hatch of overwintered eggs of the strawberry aphid, Chaetosiphon fragaefolii (Cockerell), at five temperatures in controlled environment chambers was used to determine the thermal threshold of development. Samples of eggs were taken from two field locations several times before hatch. These samples were subdivided and placed into two or three different constant temperature chambers. The day-degree requirements for hatching from the time of collection were estimated. These estimates corresponded to the number of day-degrees actually accumulated in the field between the time of egg collection and the time of hatching.This method of simulating the effect of temperature on egg development was an accurate method of predicting the time of hatch in the field at least 3 weeks prior to the observed time.

Composition and Relative Abundance of Parasites Associated with Aphid Populations on Strawberry in Southern California

Four primary parasites and seven secondary parasites (hyperparasites) were reared from mummies of five species of aphids collected from winter plantings of strawberries in southern California in 1981 and 1982. In order of abundance, the primary parasites were Lysiphlebus testaceipes Cresson, Aphelinus semiflavus Howard, Aphidius urticae Haliday, and Ephedrus californicus Baker. L. testaceipes accounted for 47.8 and 77.1% of all primaries in 1981 and 1982, respectively, and was reared most commonly from the strawberry aphid, Chaetosiphon fragaefolii (Cockerell), in 1981 (56.3%) and from the melon aphid, Aphis gossypii Glover, in 1982 (74.5%). Dendrocerus aphidum (Rondani) and Alloxysta magourae “complex” were the most common secondary parasites, accounting for 34.6 and 19.2% of all secondaries, respectively, in 1981 and for 55.8 and 23.4% in 1982. C. fragaefolii was the most common aphid present both years, reaching damaging populations in 1982 despite the parasite activity.

Development and Estimation of Aphid Populations Infesting Annual Winter Plantings of Strawberries in California

Temporal occurrence and sampling of aphids infesting fresh market strawberries were investigated in two successive annual winter plantings in Orange County, Calif. Chaetosiphon fragaefolii (Cockerell) was the dominant species as well as the primary cause of contamination. Aphis gossypii Glover was also a contaminant, but did not reach population densities as high as C. fragaefolii. Myzus persicae (Sulzer) and Macrosiphum euphorbiae (Thomas) were less common and were of minor importance. Aphid densities in excess of a log (x + 1) value of 1.5 (30.6 aphids) per plant resulted in contaminated fruit. Populations of C. fragaefolii on the youngest or oldest leaves co-varied with total populations, but this technique was not reliable for the other species. A binomial sampling plan based on the presence or absence of aphid infestations on the oldest trifoliate leaf per plant provided an efficient and conservative estimate for determining when pesticide applications are necessary.

Setal Variation in Clonal Lineages of the Strawberry Aphids Chaetosiphon fragaefolii (Cockerell) and C. thomasi (Hille Ris Lambers) (Homoptera: Aphididae)1

The currently accepted abdominal chaetotaxy for the strawberry aphid Chaetosiphon fragaefolii is zero to one submarginal setae, whereas for C. thomasi it is seven to eight submarginal setae. Intermediates having two to six setae are common. The number and position of submarginal setae were determined for aphids collected from three locations in the Pacific Northwest, and the setal patterns of these aphids' parthenogenetic offspring were determined for several generations. Setal number and position were highly variable between siblings and generations. Either “species” readily produced offspring with setal numbers of the opposite “species.” These results suggest that a separation of C. fragaefolii and C. thomasi based on setal number may not be valid.

Resistance in Fragaria chiloensis and F. X ananassa to the Aphids Chaetosiphon fragaefolii and C. thomasi1

Abstract Nine commercial strawberry cultivars (Fragaria X ananassa Duch.) and 557 clones of wild F. chiloensis (L.) Duch. from the Pacific coast of the United States were tested in the field for resistance to strawberry aphids (Chaetosiphon spp.). No cultivar was highly resistant but ‘Benton’ consistently supported fewer aphids than the other cultivars. In the first evaluation year, 29 clones of F. chiloensis had fewer aphids than the highly resistant ‘Del Norte’ clone of F. chiloensis on 5 sampling dates, although the differences were not statistically significant but in the second year, only 1 clone, RCP-37, had fewer aphids than ‘Del Norte’.

Breeding Strawberries for Resistance to the Aphids Chaetosiphon fragaefolii and C. thomasi1

Abstract Segregation for resistance to the strawberry aphids, Chaetosiphon fragaefolii (Cockerell) and C. thomasi (Hille Ris Lambers), occurred in the first backcross from the resistant ‘Del Norte’ clone of Fragaria chiloensis (L.). Aphid populations on ‘Del Norte’ were 4 and 7% of those found on the susceptible cultivar ‘Totem’ in greenhouse and field evaluations respectively. Resistance of the most resistant backcross seedlings was comparable to that of the F1 parent but slightly less than ‘Del Norte’. Greenhouse and field evaluations gave generally similar results although field evaluations have greater practical significance.

Electrical Measurement of Feeding by the Strawberry Aphid1 on Susceptible and Resistant Strawberries and Nonhost Plants2

Probing behavior of the strawberry aphid, Chaetosiphon fragaefolii (Cockerell), whose principal natural host is strawberry ( Fragaria spp.), was measured electrically. The plants tested were strawberry, Fragaria × ananassa Duchesne, cv. ‘Northwest’ and F. vesca L. var. ‘Alpine’ (susceptible hosts), strawberry selections ‘72-69-T’ and ‘Del Norte’ clone of F. chiloensis L. (resistant strawberries), and red raspberry, Rubus idaeus L., and broadbean, Vicia faba L. (nonhost plants). Although the aphid tended to probe less on broadbean, some individuals ingested for long periods of time. Feeding for 3- or 12-h periods was similar on all the other test plants. In longevity studies, the aphid survived well on Alpine strawberry but poorly on 72-69-T and Del Norte strawberries, raspberry, and broadbean.

Suitability of Plictran® and Pirimor® for Use in a Pest Management Program on Strawberries in Southern California

Plictran® (tricyclohexyltin hydroxide) at 0.25 and 0.75 lb AI/acre controlled Tetranychus urticae Koch but had measurable adverse effect on Phytoseiulus persimilis Athias-Henriot and predaceous insects. Although significantly fewer T. urticae occurred in plots receiving Plictran at 0.75 than at 0.25 lb, there was no significant difference in yield (25.1 and 25.3 tons/acre). These yields were significantly greater than that of the untreated check (19.8 tons/acre). Pirimor® (2-dimethylamino) 5,6-dimethyl-4-pyrimidinyl dimethylcarbamate) at 0.125 and 0.25 lb AI/acre controlled Chaetosiphon fragaefolii (Cockerell), Aphis gossypii Clover, and Macrosiphum euphorbiae (Thomas), but had no significant effect on T. urticae or P. persimilis . Significantly fewer predaceous insects occurred in the Pirimor 0.25 lb treatment, although there was no significant difference in the number of prey ( T. urticae ).

Effect of Phorate on the Twospotted Spider Mite, Associated Predators, and Aphids on Strawberry in Southern California

The effect of a preplanting application of phorate on Tetranychus urticae Koch, associated predators, and aphids on strawberry was investigated in southern California in 1969–70. The spider mite population was significantly lower in the phorate plot from March 3–April 28, reaching a peak averaging 226.8 active stages per leaflet on May 5, compared to 445.5/leaflet in the check on April 28. Except for March 24 and April 14, the predator population was significantly higher in the check plot from March 17–May 12. Scolothrips sexmaculatus (Pergande) and Geocoris spp. were the most common predators present. The seasonal mean number of spider mites and predators was significantly lower in the phorate plot and the mean fruit yield (g/plant) was significantly higher. The aphid population never exceeded an average of 0.3 aphids per leaflet in the phorate plot compared to a peak of 59.2/leaflet in the check on March 24. The strawberry aphid, Chaetosiphum fragaefolii (Cockerell), comprised 96% of the aphid population. The use of phorate in an integrated control program for strawberry pests is discussed.

Fragaria chiloensis Clones Resistant to the Strawberry Aphid1

Abstract The ‘Del Norte’ and ‘Yaquina’ clones of Fragaria chiloensis (L.) Duchesne exhibited a high degree of resistance to the strawberry aphid, Chaetosiphon fragaefolii (Cockerell), but a third clone, ‘OR-US 3162’, was very susceptible. Resistance of ‘Del Norte’ was transmitted to progeny when crossed with commercial strawberry cultivars, Fragaria × ananassa Duch. None of 30 commercial strawberry cultivars and advanced selections tested showed resistance to this aphid.

Influence of Cytokinin (N6Benzyladenine) on Development and Alary Polymorphism in Strawberry Aphid Chaetosiphon Fragaefolii1,3

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.

An Ecological Study of Aphids 1 on Strawberry in Southern California

Population growth trends of aphids and their natural enemies were studied on a summer planting of ‘Torrey’ variety and a winter planting of ‘Sequoia’ variety strawberries in southern California. Leaflets were sampled at weekly intervals from Sept. 21, 1967, through June 25, 1968, from a summer planting and from Dec. 3, 1968, through June 24, 1969, from a winter planting. The melon aphid, Aphis gossypii Glover; potato aphid, Macrosiphum euphorbiae (Thomas); and the strawberry aphid, Chaetosiphon frogaefolii (Cockerell) were the most common species present, with the strawberry aphid the most abundant, especially during the spring months. The braconid Lysiphlebus testaceipes (Cresson) was the most common primary parasite reared from aphid mummies, and Alloxysta bakeri (Kieffer) and Asaphes sp. were the two most numerous hyperparasites. Altogether, 4 primary and 8 secondary parasites were reared from the 3 species of aphids. The pathogenic fungus Entomophthora planchoniana Cornu was a primary mortality factor affecting the aphid populations, especially the strawberry aphid.

Relationship between parent size and the production of winged forms in the strawberry aphid, Chaetosiphon fragaefolii

Parent strawberry aphids, Chaetosiphon fragaefolii, reared in isolation on disks of Fragaria vesca exhibit size (length) differences presumably induced by variation in the nutritional uptake. A positive correlation was observed between increasing size of the parent aphid and the production of alate offspring. Parent aphids reared on severely deteriorated leaf disks were smaller and produced fewer alatae than when reared on fresh leaf disks. These findings appear contrary to the opinion that alate forms occur under conditions of diminishing nutrition. Temperatures above and below the optimal larviposition temperature (20·0°C) during parturition resulted in a decline in alate production. A temperature of 23·9°C during development resulted in reduced size and reduced production of alate offspring irregardless of temperatures during parturition. A temperature of 15·5°C during development had no significant influence on size or alate production when compared to 20·0°C.

Population Dynamics of the Strawberry Aphid 1 in Southwestern Washington 2

Chaetosiphon fragaefolii (Cockerell) was studied to determine the factors regulating its populations. Fertilizers, irrigation, defoliation to stimulate production of new leaves, and removal of blossoms had only temporary effects or none on populations. Aphid populations were much larger on plants covered by cages in the field, indicating that predators were an important controlling factor. However, parasitized aphids were never found. Populations became even larger in an unheated greenhouse and remained large through the winter, even at subfreezing temperatures, whereas populations became low in field cages. Wind and rain probably are detrimental to the aphids. The field population always declined in the late summer, even in cages. Analysis of strawberry foliage showed that populations of this aphid tend to correlate with the concentration of nonreducing sugars (probably mostly sucrose). Decline in nutritional value of the leaves coupled with increasing predator populations are probably the prime reasons for the rapid drop in population size in mid- to late summer each year.

Effects of temperature, photoperiod, and host plant on alary polymorphism in the aphid, Chaetosiphon fragaefolii

Apterous viviparae of Chaetosiphon fragaefolii, which developed in isolation at a temperature of 23·9°C, deposited significantly fewer alates than did those developing at 15·6°C. No post-natal suppression of alate determination was apparent at the temperatures investigated. A decline in alate production occurred within 1 day when reproducing adults were transferred from 15·6 to 23·9°C. A reduced photoperiod during parental development enhanced the production of alate offspring. Photoperiod or intensity did not appear to act via the host plant. Parental nutrition appeared to exert a major influence on the production of alate offspring. More alates were produced by parent aphids reared on old leaves of Fragaria vesca than when reared on young leaves. The effect was particularly marked during the winter months. Parent aphids reared on F. vesca produced more alates than those reared on F. chiloensis. More alates were produced when parents were reared on leaf disks floated on sucrose solution than when the disks were floated on distilled water.