Agalliana ensigera Oman

Description & Identification

Small, linear species. Length of male 2.90—3.10 mm., female 3.25—3.50 mm. (Nielson, 1968)General color light brown to almost black. Vertex with two distinct black spots; pronotum speckled with brown or black in female, nearly completely dark brown or black in males; elytra with veins brown or black.(Nielson, 1968)Pygofer in lateral aspect slightly longer than wide, caudal margin produced posteriorly at about middle to bluntly angled lobe; 10th segment with pair of long curved, spines directed posteroventrad along inner submargins of pygofer; aedeagus in lateral aspect recurved, shaft irregularly tubelike, apex with distinct hook or curved spine, pair of spines on ventral surface of shaft directed caudad; gonopore terminal; style in dorsal aspect bibbed, inner lobe distinctly triangulate at distal half, outer lobe narrowed apically; female 7th sternum in ventral aspect with caudal margin truncate, notched medially. (Nielson, 1968)This Species, closely related to sticticolbis, can be separated by the 10th segment, which has a pair of long saberlike spines.(Nielson 1968)

Biology & Ecology

The biology of this species is fairly well known. In 1946, Bennett et al. (61) reported that the favorite host plant in Argentina was sugarbeet and a thousand or more individual leafhoppers could be reared from a single large plant. Nymphs hatched from eggs in 9 days at temperatures of 100° F. and developed into adults in about 25 days. In the province of Tucumán populations were abundant on sugarbeets, mangel-wurzel, and a number of other herbaceous plants, such as Amaranthus, Portulaca, Daunra stramonium L., Zinnia elegans Jacq., and Chenopodium album L. It was not found on any native shrubs or plants outside of the cultivated region. Apparently the native hosts in Argentina are unknown. They also reported that the species failed to live or breed on tomato or tobacco.Costa in 1952 (147) stated that this species was abundant on many cultivated weeds and plants in the State of São Paulo, Brazil. It was reared on spiny bur, Atropa belladonna L., Callistephus chinensis (L.) Nees, Crotalaria juncea L., C. lanceolata E. Mey., jimsonweed, Nicotiana paniculata L., Solanum nigrum L., sunflower, and Solanum tuberosum L; Costa specifically pointed out the ease with which the species fed and bred on tomato, contrary to reports by Bennett et al. in 1946 (61). (Nielson, 1968)

Worldwide Distribution

This species occurs in South America. Oman in 1934 (578) examined specimens from numerous localities in Argentina and from Piedra Blanca, Bolivia. It has been reported from the State of São Paulo, Brazil, by Costa in 1952 (147). (Nielson, 1968)

Vector Status

Economic Crops

This species is a vector of Argentine curly top virus of sugarbeet and the solanacearum strain of Brazilian curly top of tomato in South America. In the early work on Argentine curly top of sugarbeet, Fawcett in 1925 (253) first suspected that the virus was transmitted by a leafhopper, which was determined as 'Aceratagallia sanguinolenta (Prov.) .' Later Fawcett in 1927 (254) proved transmission of the virus by a leafhopper subsequently identified as Agallia sticticollis (StAl). Oman (578) in his 1934 review of the South American agalliine leafhoppers restudied Fawcett’s material and determined the species as Agalliana enzsigera.Confirmation of Fawcett’s work was reported by Bennett et al. in 1946 (61) in an excellent account of symptomology, host range, and transmission of the virus. Experimental transmission was effected to several varieties of sugarbeets, chickweed, and zinnia, but not to any member of Sobanaceae, including tomato, tobacco, red-pepper, and petunia. Percent transmission ranged from 10 to 52. The minimum incubation period of the virus iii the insect was 24 to ‘72 hours. Leafhoppers retained the virus after feeding on immune plants for 36 days. Limited tests indicated that the virus did not pass through the egg.Transmission of a new virus of tomato distinct from the braziliensis variety of Ruga verrucosans was reported by Costa in 1952 (147). This virus causing tomato curly top and named solanacearum variety of R. verrucosans was transmitted by ensipera but not by Agallia albidula., and thereby the two viruses were proved to be distinct. The new virus had a restricted host range of tomato currant tomato, jimsonweed, and Solanum nigrum. Single leafhopper inoculations gave 50- to 60-percent transmission with a higher percentage for females than for males. The incubation period of the virus in the vector varied from 16 to 24 hours. The virus was retained by infective insects for 46 days and by leaf-hoppers transferred daily on a series of tomato seedlings for 31 days. There was negative evidence of transovarial passage of the virus.(Nielson 1968)This species is the most important vector of Argentine curly top Virus of sugarbeet and tomato curly top virus (var. solanacearum) in Brazil. The evidence supporting differences in the ability of ensigera to live and breed on tomato is highly significant, especially in view of the geographical proximity of Brazil and Argentina, where one would normally expect no great difference in host response or preference. Yet preference for breeding hosts was wide; sugar-beets and mangel-wurzel in Argentina and tomato, tobacco, and sunflower in Brazil. A. ensigera was finally identified as the test population in the early work of Fawcett from 1925 and 1927 (253, 254) on sugarbeet curly top and also as the species used by Costa (147) on tomato curly top. Determinations were made by P. W. Oman. There were, however, no citations or references indicating that a specialist had determined specimens used by Bennett et al. in 1946 (61) in their confirmatory work on sugarbeet curly top. The authors apparently assumed they were working with ensigera as evidenced by their citation to Oman’s 1934 (578) clarification of the species. It is evident, therefore, that a thorough investigation is warranted on species-host relationships of both populations occurring in Argentina and Brazil. Such a study should be conducted at one location. Moreover, the taxonomic status of each population needs further clarification through reexamination of material used in transmission tests involving both viruses(Nielson 1968)

Plant Diseases