Macrosteles fascifrons (Stål 1858e: 194 )Membracoidea : Cicadellidae
|Diseases Transmitted||Pathogen Type|
|Crops Affected by Macrosteles fascifrons (Stål 1858e: 194 )|
This species is a well-known vector of the eastern and western strains of North American aster yellows virus. it is also a reported vector of little cherry virus in British Columbia, oat blue dwarf virus in Canada, clover phyllody virus in Canada, and clover proliferation virus in Canada.
Kunkel in 1924 (422) was first to report this species as a vector of plant viruses when he demonstrated the transmission of aster yellows from diseased aster to healthy aster plants in New York. He believed that the insect was responsible for most if not all of the natural spread of the virus in New York City. He then in 1925 (423) confirmed transmission and showed that although the virus was specific to the insect, the virus had a wide range of host plants. The virus was transmitted experimentally to 50 species of plants in 20 families. Twenty additional host plants of the virus were reported by Kunkel in 1928 (426) and two species of plants, Plantago major L. and P. lanceolata L., were found to be susceptible and immune, respectively, to the virus. It was also demonstrated that aster yellows virus was distinct from the witches’ broom virus of potatoes.
In California in 1929 Severin (687) reported transmission of yellows virus of celery from diseased celery to healthy celery, lettuce, and other plants. This was the first demonstration that yellows of celery was identical with aster yellows previously reported in studies by Kunkel. Later, in 1932 Severin (690) confirmed the similarity of aster yellows with yellows of celery and other plants by transmitting the virus from diseased celery, parsley, and carrots to healthy plants including aster. Many additional host plants of the virus were reported by Kunkel in 1931 (427) when he transmitted the virus by means of the leafhopper to 120 plants in 30 families.
Transmission of aster yellows to flax in California was reported by Severin and Houston in 1945 (713). In 1945, Severin and Freitag (710) found that the virus overwintered in biennials, perennials, and adult leafhoppers. Severin and Frazier in 1945 (709), Severin and Freitag (710) in 1945, and Frazier and Severin in 1945 (278) reported additional hosts of the virus in California. Fourteen species in 6 families of vegetables and seed crops, 45 species in 17 families of ornamentals, and 41 species in 14 families of weeds were infected experimentally with the virus. In 1962, Freitag (284) transmitted western aster yellows virus to 15 species of legumes and 7 species of solanaceous plants including tomato.
Freitag and Tompkins in 1963 (289) transmitted the virus in California from infected gladiolus to plantago, aster, celery, Vinca rosea L—, and Nicotiana rustica L. and back to healthy aster from diseased gladiolus. The virus caused a peculiar symptom on gladiolus called corkscrew, and transmission experiments proved it was caused by the western strain of aster yellows. Transmission of the virus carrying purple top wilt to potato was first reported by Severin and Haasis in 1934 (711) and confirmed by Younkin in 1943 (884) and Jensen and Tate in 1947 (402).
In 1940, Severin (692) discovered two races of the six-spotted leafhopper in California showed that both were capable of transmitting the virus from infected potato to healthy asters. He also demonstrated transmission of the virus to perennial delphiniums by both races, but poor transmission was obtained owing to the inability of the vectors to survive very long on delphiniums, found in 1946 (698). Transmission was effected from naturally infected annual larkspurs to aster, discovered in 1942 (694) and naturally infected phlox to a healthy phlox by both forms which was realized in 1943 (695).
In 1945, Severin and Frazier (709) were able to transmit the western strain to onions, but attempts to transmit the eastern strain failed. Both short-winged and long-winged forms were used. Another difference between the two virus strains was found in 1945 when Frazier and Severin (278) demonstrated transmission of the western strain to three species of legumes. Additional studies by Severin in 1947 (701) showed that percent transmission of California aster yellows to celery and aster by the short-winged form was 69 and 69, respectively, and by the long-winged form 9 and 62, respectively. In 1934 Severin (691) found that celery was highly resistant to aster yellows obtained from New York, Indiana, Maine, Idaho, and Wisconsin, but not from California.
In 1956, Freitag (283) transmitted California aster yellows virus to squash, pumpkins, and cucumber. In 1958 Maramorosch (482) demonstrated transmission of the eastern strain to 38 of 40 plants and the California strain to 23 of 40 plants. In 1958, Strong and Rawlins (776) transmitted eastern aster yellows strain to lettuce. From 70 to 78 percent of the viruliferous leafhoppers inoculated all plants on which they were confined individually. In 1958 Lee and Robinson (448) found the western strain of aster yellows virus in Manitoba. Banttari and Moore in 1960 (44) transmitted the virus to barley. Chiykowski in 1965 (140) confirmed transmission to barley and infected 24 varieties with both strains of the virus. Differences in reaction of barley varieties to virus strains were noted.
The incubation period of the virus in the insect’s body and plants has been studied in detail. Kunkel in 1926 (425) determined that the incubation period of the virus in nymphs was 2 weeks or more and in adults from 6 to 10 days. The infective leafhoppers never lost their ability to transmit the virus, He found that the virus was carried in adult insects for more than 100 days, although some individuals lost the ability to transmit in a short time after they became infective. The virus was not transmitted through the eggs of the insect or seeds of aster (Kunkel 1926 ).
In 1953, Maramorosch (476) found the shortest period in plants was 8 days in the greenhouse and 9 days under controlled conditions at 25° C. At 20° the minimum period was 18 days and none of the plants became diseased at 10°. The incubation period in insects ranged from 12 days at 25° and 11 days at 30° to 16 days at 20°. However, transmission was not affected in the same degree at low temperatures, but gradually ceased at 30°.
Difference in incubation periods between the eastern and western strains of the virus was determined by Maramorosch in 1962 (488). The minimum incubation period in insects at 25° was 12 days for the eastern and 11 days for the western strain. Under optimum conditions in the greenhouse, the minimum periods were 9 and 8 days, respectively. In plants the shortest period was 10 days for the western strain and 9 days for the eastern strain. There was a 5-day span between the shortest and longest period in the eastern strain and 10 days for the western strain.
In 1962, Lee (442) studied the acquisition and inoculation time in transmission of the western strain. Single leafhoppers were unable to transmit the virus of less than 2 hours’ acquisition feeding time. After that, transmission was an exponential function of both acquisition and inoculation periods. Fluctuation in transmission of the virus over a 16-hour period was reported by Maramorosch in 1964 (495). Transmission was less frequent during the first 8 hours of each day and five distinct peaks, two in the morning and three in the afternoon, were consistently detected.
In 1952, Maramorosch (474, 475) found no evidence that the eastern strain could multiply in or be transmitted by the leafhopper Dalbulus maidis (DeLong & Wolcott), indicating further evidence of virus-vector specificity.
Black (77) offered evidence of multiplication of the aster yellows virus in the vector’s body by passing the virus from insect to insect using dilutions of infective juices as high as 1:1,000. The virus multiplied a hundredfold between 2 and 17 days of a 17-day incubation period. Concentration of the virus was highest 6 days before it was transmitted to aster plants. The incubation period varied between 11 and 45 days and the insects were viruliferous for life.
Direct evidence of multiplication has been obtained by Maramorosch in 1950 and 1955 (472, 479, 480). He injected extracts of viruliferous leaf-hoppers into virus-free insects. Serial passage from insect to insect was attained as high as 10 times. The estimated dilution used to inoculate the 10th group of insects, if no multiplication occurred, would have been 10-40, but the dilution end point was below 10-4. It was concluded that the virus multiplied in body cells of the leafhopper.
Heat treatment of the vector for 12 days at 31° to 32° C. caused permanent loss in the ability to transmit the virus (Kunkel 1937 ). Kunkel also found that infective colonies subject to these temperatures for periods of less than 12 days temporarily lost their ability to transmit the virus, and when they did transmit, only a mild strain of the virus was transmitted. Mechanical transmission obtained by injecting virus from infective leafhoppers to previously noninfective specimens rendered them capable of transmitting the virus.
Littau and Maramorosch in 1956 (467) found evidence of cytological effects of the virus on fat cells of leafhoppers. Studies comparing 42 viruliferous and 38 nonviruliferous insects showed that all infected leafhoppers had abnormal cells in the fat body whereas noninfected leafhoppers were normal. The effect of virus on these cells apparently did not affect longevity of adult leafhoppers, as evidenced in tests by Severin in 1947 (702). He found no beneficial or deleterious effect on the longevity of infective short-winged and long-winged forms of the leafhopper.
Transmission of little cherry virus was first reported by Wilde in 1960 (861). In tests in British Columbia 7 cases of transmission were obtained in the greenhouse and 18 cases in the field from sweet cherry to sweet cherry. The leafhoppers were fed from 2 to 48 hours on diseased cherry trees, then transferred to immune barley or rye for 20 to 30 days. Surviving insects were placed on healthy trees. Symptoms did not appear until the second, third, or fourth year. Confirmation of Wilde’s work has not been reported.
Banttari and Moore in 1962 (45) were first to report the transmission of oat blue dwarf virus in Minnesota. The leafhoppers were fed on infected blue dwarf oat plants for 14 days and on healthy oat plants for 11 days. Six of 34 plants tested developed symptoms in about 3 weeks. in subsequent experiments, leafhoppers were fed from 15 days to 7 months on diseased plants and transferred to healthy oat and barley plants for 6 to 20 days. The acquisition feeding of and incubation periods in the vector were not more than 15 days. A minimum of 6 days on healthy plants produced low infections, but a greater percentage of plants were infected when the transmission feeding period was increased to 20 days. A transmission feeding time of 6 days produced 7-percent infections in oats and 13 percent in barley. A 20-day transmission feeding period produced 88-percent infections in oats and 92 percent in barley. The virus was also transmitted to a high percentage of flax plants. The investigators proved that the oat blue dwarf virus was distinct from aster yellows virus by demonstrating that the former virus did not attack aster and the latter virus did not attack oats.
In 1962 and 1964, Fredrickson (279, 280) obtained simultaneous transmission and infection of both viruses in flax by the six-spotted leafhopper. After a 15-day minimum incubation period, the viruses were passed at the same time and one virus did not inhibit the transmission of the other, although under certain conditions one may have masked symptoms of the other.
Transmission of clover phyllody by fascifrons was first reported in Canada by Chiykowski in 1962 (135). He transmitted four isolates of this virus from Ladino clover, aster, and periwinkle to 79 of 86 aster plants, 5 of 13 periwinkle plants, and 9 of 29 Ladino clover plants. The shortest period the insect acquired the virus was 24 hours. The minimum incubation period recorded was between 20 and 27 days. The longest incubation period was between 36 and 43 days. In joint transmission tests with clover phyllody and aster yellows viruses a longer incubation period was required in the insect for clover phyllody virus than for aster yellows. The same held true in plants. The range of clover phyllody virus was limited to Provinces of Quebec, New Brunswick, Nova Scotia, and Prince Edward island.
Confirmation was also reported by Chiykowski in 162 (136) by demonstrating transmission from strawberry to clover and aster plants and thereby he proved that clover phyllody and green petal of strawberry were caused by the same virus. Mechanical transmission of the virus to its vector was obtained by Lee and Chiykowski in 1963 (446). In four trials the insects became infective after injection with supernatants of macerated viruliferous leafhoppers. Eleven of 14 aster plants were infected.
In 1964 and 1965 Chiykowski (139, 141) transmitted clover proliferation virus of alsike clover, which was apparently closely related to aster yellows and clover phyllody. The diseased plants found in Alberta more closely resemble aster yellows than clover phyllody. Transmission was effected to aster and periwinkle, which took on a witches’ broom appearance. The vector was not very efficient, and only 1 percent of the insects acquired the virus after feeding for 1 day. When fed for 16 days, 18 percent became infective. The latent period ranged from a minimum of 21 to 28 days to a maximum of 65 to 79 days.
This species is unquestionably the most important vector in the spread of North American aster yellows viruses, little cherry virus in British Columbia, and oat blue dwarf virus in Minnesota. It is also one of the important vectors of clover phyllody virus and clover proliferation virus in eastern Canada.
Small, linear species. Length of male 3.20—3.40 mm., female 3.50—3.80 mm.
General color yellow. Crown yellow with row of three spots on each side of middle; pronotum yellow; scutellum yellow with two spots on anterior margin; elytra light yellow, subhyaline.
Pygofer in lateral aspect about as long as wide, caudoventral margin with small lobe, caudal margin truncate; aedeagus in lateral aspect tubelike throughout with pair of terminal processes; lateral margins of shaft smooth in ventral aspect; gonopore terminal; style in dorsal aspect simple, apex narrowed; female seventh sternum in ventral aspect with caudal margin slightly rounded.
This species is similar to the cristata complex, but can be separated by the aedeagus, which lacks the flange on the dorsal surface of the shaft. According to Beirne in 1952 (54), fascifrons is a complex of various forms that intergrade in morphological characters, Distinct forms are known in California, which are not able to interbreed and are characterized as the “shortwinged” and “long-winged” forms. Eastern forms of the species are typical of quadrilinatus Forbes, which Beirne considered as a synonym of fascifrons. The entire complex is variable in size of head and pronotum and color markings on these structures.
|Nielson, M. W. 1968b. The leafhopper vectors of phytopathogenic viruses (Homoptera, Cicadellidae). Taxonomy, biology and virus transmission. United States Department of Agriculture Technical Bulletin . 1382 386 pp.|