Edwardsiana froggatti (Baker) -- Hemiptera, Cicadellidae
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The European apple leafhopper invaded New Zealand and Australia around 1918, later in 1929 showing up in Tasmania as well. It attacks prunes, plums, apples and Crataegus sp.. The nymphs and adults feed on the foliage and deposit copious amounts of honeydew on both foliage and fruit. Dumbleton (1934) in New Zealand found two generations per year, with the winter passed in the egg stage under bark of twigs. Heavily infested apple trees had an egg population averaging almost five per inch of twig (Clausen 1978). The eggs hatch in springtime or early in summer, and the adult stage is reached after a nymphal period of 5-6 weeks. Adults live 1-2 months. The incubation period of the summer brood takes ca. 30 days. Eggs are laid in the midribs and veins of the leaves rather than under the bark.
Field-collected overwintering eggs of E. froggatti with developing mymarid parasitoids Anagrus armatus nigriventris Girault, were imported into Tasmania from New Zealand during the winter of 1935. Two colonies of adults from this material were placed in gardens of Hobart and one in an orchard at Risdon. The parasitoid became established (Evans 1937) but there is no further information on a later distribution program.
The dryinid parasitoid Aphelopus typhlocybae Muesebeck was imported into New Zealand from the United States in 1935. There were 239 adults of this nymphal-adult parasitoid released (Dumbleton 1937), but the species did not establish. This parasitoid frequently attains a high parasitization rate in North America, and would be a useful complement to A. armatus nigriventris. The latter parasitoid was introduced into South Australia in 1940 and Western Australia in 1943 and 1947-48, the stocks being obtained from Tasmania, but neither colonization attempt succeeded (Wilson 1960).
In Tasmania the Anagrus populations increased rapidly following initial releases, as indicated by high field parasitization at release sites within 18 months after release (Evans 1937). Ten years later Miller (1947) recorded up to 90% parasitization of the eggs and stated that the leafhopper had not been a serious pest in the preceding years. Wilson (1960) also commented on the reduction in seriousness of the outbreak.
Anagrus armatus nigriventris is common in North America where it attacks the eggs of several Cicadellidae. It was found to be abundant as a parasitoid of E. froggatti in New Zealand in 1932. Examination of field collected overwintering eggs showed parasitization rates ranging from 78-93%, indicating that the species is potentially a valuable control agent. However, even this high parasitization is not sufficient to bring the pest to a consistently noneconomic level under New Zealand conditions (Clausen 1978). Winters are passed in the larval stage within the host eggs and the first brood of adult emerges in November and December, at a time which is correlated with the presence of summer eggs of the host at this Southern Hemispheric location. The second brood of adults is present from January to April. Two generations occur each year on leafhopper eggs on apple, whereas on hawthorn there is only a partial third generation. Females are very short lived, and may deposit up to 20 eggs in rapid succession. The spring brood of adults show a preponderance of females in the ratio of about 9:1 (Dumbleton 1934).
In Canada Armstrong (1936) studied Anagrus as a parasitoid in the eggs of Typhlocyba pomaria McA. and found that it passes the winter as a partially grown larva in the host egg and that there are two and perhaps three generations each year. Parasitization of the overwintering host eggs averaged 74.8% and those of the summer brood 40.4%. The peak period of emergence of the first brood of adults was around July and of the second around early August. The sex ratio of material reared during an entire season was 2.3 females to 1 male.
REFERENCES: [ Additional references may be found at: MELVYL Library ]
Armstrong, T. 1936. Two parasites of the white apple leafhopper (Typhlocyba pomaria McA.). Ent. Soc. Ontario, Ann. Rept. 66 (1935): 16-31.
Clausen, C. P. 1978. Cicadellidae. In: C. P. Clausen (ed.), Introduced Parasites and Predators of Arthropod Pests and Weeds: A World Review. U. S. Dept. of Agric., Agric. Handbk. No. 480. 545 p.
Dumbleton, L. J. 1934. The apple leaf-hopper (Typhlocyba australis Frogg.). New Zealand J. Sci. Technol. 16: 30-8.
Dumbleton, L. J. 1937. Apple leaf-hopper investigations. New Zealand J. Sci. Technol. 18: 866-77.
Evans, J. W. 1937. The biological control of the apple leaf-hopper (Typhlocyba froggati Baker). Tasmanian J. Agric. 8: 171-73.
Miller, D. 1947. Entomological investigations. Cawthron Inst. (Nelson, New Zealand) Ann. Rept. 1946-1947: 34-5.
Wilson, F. 1960. A review of the biological control of insects and weeds in Australia and Australian New Guinea. Commonwealth Inst. Biol. Control, Tech. Commun. 1: 102 p.