Aculops lycopersici (tomato russet mite)

Aculops lycopersici (Tryon, 1917) is the correct name for the tomato russet mite. Tryon published a brief description of the damage caused by the mite and proposed the name Phyllocoptes lycopersici. Massee (1937) considered Tryon's description to be inadequate and the name to be a nomen nudum. He redescribed the mite as a new species under the same name, Phyllocoptes lycopersici, and most subsequent authors have attributed the name to Massee. However, as pointed out by Amrine (1994), Tryon's description and name take precedence over Massee's under Article 12b(8) of the International Code of Zoological Nomenclature. There is now general agreement that the name Phyllocoptes destructor Keifer is a junior synonym of Phyllocoptes lycopersici Tryon.

Adults of A. lycopersici were well described and illustrated by Keifer (1940) under the name Phyllocoptes destructor Keifer. Additional useful data and interpretations are found in Bailey and Keifer (1943), Lamb (1953a) and in Perring and Farrar (1986). Adult females are the most abundant and frequently encountered instar on symptomatic plants. They have the basic characters of Eriophyidae and Phyllocoptinae. The body is fusiform and from 150 to 200 µm long. The prodorsal shield is 40 to 50 µm long, has a broad, short anterior lobe that is abruptly deflected ventrally; is strongly sculptured with a diagnostic hourglass-shaped pattern of longitudinal striations, and bears a pair of moderately long, posteriorly-directed, divergent dorsal setae near the posterior edge. The body exhibits a series of annuli strongly differentiated into tergites and sternites. There are 25-30 tergites and more than 60 sternites, and the sternites bear pointed microtubercles at their posterior edges. The genital coverflap ranges from 14-16 µm in length and is sculptured with longitudinal striations. The two pairs of legs have distinctive claw-like structures terminally on the tarsi, termed feather-claws, with four pairs of rays.

A. lycopersici probably now occurs in all countries where tomatoes and related solanaceous crops are grown.

A. lycopersici is most often reported as a pest of tomatoes, but utilizes a wide range of Solanaceae, including several crop plants, as secondary hosts. The mites require perennial alternate hosts in order to survive during winter and, as a result of the catastrophic injury they cause to tomato plants, after death of their primary hosts.

Members of A. lycopersici feed on the foliage, inflorescence and young fruit of tomato plants causing shrivelling and necrosis of leaves, dropping of flowers, russeting of fruit and, if uncontrolled, death of the plants (Keifer et al., 1982). Feeding by the mites damages epidermal tissue (Royalty and Perring, 1988) and guard cells thereby inhibiting gas exchange and photosynthesis (Royalty and Perring, 1989). The mites cause similar, but usually less severe, injury to related solanaceous crops.

Eriophyoid mites can be identified with certainty only by examining properly cleared and slide-mounted specimens under high magnification. Members of A. lycopersici resemble members of other species of Aculops, but can be distinguished using the diagnostic character states listed by Keifer (1940), Bailey and Keifer (1943), Lamb (1953a) and Perring and Farrar (1986).

In field situations, airborne adults of A. lycopersici begin to infest tomatoes perennial alternate hosts shortly after transplanting (Bailey, 1942; Michelbacher, 1943; Sloan, 1945; Keifer, 1952; Ramalho, 1978). Females begin to oviposit soon after becoming established on the host, giving rise to a succession of generations (up to seven per growing season) that can develop from egg to adult in as little as 6 or 7 days each under optimum conditions of 26.5°C and 30% RH (Bailey and Keifer, 1943; Anderson, 1954; Wilcox and Howland, 1954; Rice and Strong, 1962; Gerdzhikov, 1968; Jeppson et al., 1975; Osman, 1975; Flechtmann, 1977; Abou-Awad, 1979). Consequently, populations increase rapidly to very high densities with catastrophic impact on the vitality of the host, especially under dry weather conditions (Holdaway, 1941). When the primary host dies, some of the mites are dispersed by wind to nearby alternative hosts where they form overwintering aggregations. In greenhouses, the sources of infestation of young plants are surviving populations of mites on remnants of previous crops of infected plants or mites newly introduced on young plants. Perring (1996) summarized information on the biology of A. lycopersici.A. lycopersici has been implicated as a vector of the fungal pathogen Hirsutella thompsonii (Cabrera and McCoy, 1984).

Hessein and Perring (1988) reported predation of A. lycopersici by a tydeid mite Homeopronematus anconai. Osman and Zaki (1986) investigated the predation efficiency of the stigmaeid mite Agistemus exsertus against A. lycopersici. Sabelis (1996) summarized information on reported phytoseiid mite predators of A. lycopersici.

A. lycopersici may cause serious reductions in yield in tomato crops, especially when young plants are exposed to attack. Losses of up to 65% have been reported in situations where young plants have become heavily infested shortly after transplantation (Eschiapati et al., 1975; Oliveira et al., 1982).

Field infestations of A. lycopersici are detected by inspecting the foliage of symptomatic plants.

Chemical Control

Approaches have changed from repeated application of broad spectrum insecticides to focused treatment of young plants to prevent establishment of A. lycopersici early in the growing season (Anon., 1934, 1942, 1951, 1972; Morgan, 1935; Cottier and Taylor, 1937; Sloan, 1938, 1941, 1945; Veitch, 1938; Keifer, 1940; Lockwood, 1940, 1942; Pescott, 1940; Planes, 1941; Bailey, 1942; Campbell, 1942a, b; Watson and Tissot, 1942; Bailey and Keifer, 1943; Wilcox and Elmore, 1943; Michelbacher, 1944; Michelbacher et al., 1948, 1950; Wilcox and Howland, 1950, 1954, 1956; Lamb and Jacks, 1952; Tuft and Anderson, 1953; Anderson, 1954; Blanck et al., 1954, 1956; Smith, 1955; Smith and Saunders, 1956, 1960; Rice and Strong, 1962; Tsalev, 1967; Gerdzhikov, 1968; Egashira, 1973; de Sales et al., 1973; Siqueira and Dunham, 1974; Jeppson et al., 1975; Osman, 1975; Hamilton, 1976; Kamau, 1977; Taylor, 1978; Ramalho and Leao-Veiga, 1980; Collingwood et al., 1981; Bourdouxhe and Collingwood, 1982; Vacante, 1982; Maeso and Nunez, 1983; Nunez and Maeso, 1983; Oliveira and Sponchiado, 1983; Perring and Trumble, 1984; Abou-Awad and El-Banhawy, 1985; Daiber, 1985; Perring and Farrar, 1986; Royalty and Perring, 1987; Kay and Shepherd, 1988; da Silva et al., 1988; Haji et al., 1988; Undurraga and Dybas, 1988; Costilla and Barberis, 1990; Baradaran-Anaraki and Daneshvar, 1992).

Of several acaricides tested against A. lycopersici in the field in Australia, dicofol, SLJ0312 (an experimental compound), cyhexatin, azocyclotin and sulprofos were found to be effective (Kay and Shepherd, 1988). Dicofol was recommended to control or prevent infestation of the mite. Royalty and Perring (1987) found avermectin B1 to be more toxic to A. lycopersici than dicofol, and selective doses of avermectin B1 gave good control of the pest without reducing numbers of the beneficial tydeid mite Homeopronematus anconai. Perring (1996) provides a short overview of the control of A. lycopersici.

Biological Control

Chemical methods have progressively been supplemented, especially in greenhouse situations, by increasingly well understood biological control strategies involving predatory phytoseid, stigmaeid and tydeid mites (Bailey and Keifer, 1943; Anderson, 1954; Bravenboer, 1975; Anon., 1977; Abou-Awad, 1979, 1980; de Morales and Lima, 1983; Hessein and Perring, 1986, 1988; Osman and Zaki, 1986; James, 1989; Manzaroli and Benuzzi, 1995; Brodeur et al., 1997). Integrated pest management of A. lycopersici in greenhouses has been reported in a number of recent studies (Berlinger et al., 1988; Arno et al., 1994; Atanasov et al., 1995).