Kotinsky, 1915
Diagnosis
In life, scale cover of adult female 1.5-2.5 mm long, ovoid, flat, chalky white with yellow or brown terminal exuviae, and with a thick ventral scale, forming a bivalved cover (Ben-Dov, 1988; Gill, 1997) ODRUTHL2.jpg and ODRUTHL1.jpg . The scale projects from the host's surface, so resembling a dead, whitened leaf sheath of the host (Gill, 1997). Males unknown in California, but the illustration of a male scale cover by Ferris, 1938, suggests there may be a biparental race (Gill, 1997). According to Dekle, 1976, the male scale cover is similar to that of the female but is only about half the size.
Body of slide-mounted female elongate oval, membranous to lightly sclerotized, with intersegmental folds on abdomen obviously thickened and sclerotized and ducts on dorsum and venter all of similar size, in no fixed arrangement; submarginal duct tubercles absent from venter of thorax ODORUS.jpg . Pygidium with a single marginal sclerosis present on each side; perivulvar pores numbering 60-110, present in three groups (one anterior to, and two lateral to, vulva); gland spines absent. Feeds on several other plant families (including some Dicotyledonae) as well as Gramineae ODRUP.jpg .
Host range
Odonaspis ruthae is a fairly polyphagous species that has been recorded from hosts belonging to five plant families (Borchsenius, 1966; Ben-Dov, 1988). Bermuda grass (Cynodon dactylon) is the favoured host; infestation is usually on the rhizomes (Williams and Williams, 1988). Hosts include species of: Andropogon, Axonopus, Bambusa, Brachiaria, Brachypodium, Cattleya, Cenchrus, Chloris, Cortaderia, Cymbopogon, Cynodon spp., Digitaria spp., Distichlis, Echeveria, Eleusine, Eremochloa, Euphorbia, Gramineae, Hibiscus, Juncus, Lepturus, Melinis, Neyraudia, Nypa, Oplismenus, Orchidaceae, Panicum, Panicum maximum, Paspalum, Pennisetum, Setaria, Sorghum halepense, Spartina, Sporolobus and Stenotaphrum.
Affected plant stages: vegetative growing, flowering and fruiting stages
Affected plant parts: on stems under leaf sheaths or bud scales, usually around the nodes close to the ground ODRUTHL2.jpg and ODRUTHL1.jpg , sometimes also on underground stems (rhizomes), but not on roots
Biology and ecology
In California, O. ruthae is parthenogenetic and there are multiple generations each year. In USA (Georgia) there are two generations per year (Tippins and Martin, 1982). The illustration of a male scale cover by Ferris, 1938, implies that bisexual populations exist (Gill, 1997).
Crawlers are the primary dispersal stage and move to new areas of the plant or are dispersed by wind or animal contact. Mortality due to abiotic factors is high in this stage. Dispersal of sessile adults and eggs occurs through human transport of infested plant material.
Symptoms
This species causes browning and dieback of Bermuda grass, especially in the southern USA (Gill, 1997).
Economic impact
This species is a pest of pasture grasses in Chile (Claps et al., 2001a) and damages Bermuda grass and other pasture grasses in the southern USA (Gill, 1997; Costa et al., 2000); infestations are so easily overlooked that it is likely that more injury is caused than is recognized. In Israel and Egypt, O. ruthae sometimes attacks grass on lawns (Berlinger and Barak, 1981; Abou-Elkhair et al., 1994).
Detection and inspection methods
Closely examine the stems near the base of the plant beneath leaf sheaths, for ovoid, flat, chalky white scale covers, each with yellow or brown terminal exuviae and a thick ventral scale, forming a bivalved cover. The scale covers resemble the dead, whitened leaf sheaths of the host (Gill, 1997) ODRUTHL2.jpg and ODRUTHL1.jpg .
Natural enemies
Parasitoids:
- Adelencyrtus odonaspidis, in USA (Hawaii)
Predators:
- Podothrips semiflavus, in Israel
Distribution
See Odonaspis ruthae distribution.
Microscopic examination of slide-mounted adult females is required for authoritative identification to species.
Odonaspis secreta (Cockerell) ODSECS.jpg could be misidentified as O. ruthae, but differs in lacking spiracular pores beside each posterior spiracle, and in lacking any rows of ventral ducts on the metathorax that run across the mid-line. In contrast, O. ruthae ODORUS.jpg possesses spiracular pores beside each posterior spiracle, and has a row of ventral ducts on the metathorax that runs across the mid-line. Odonaspis secreta has been recorded from China (Jiangsu, Zhejiang, Hunan, Yunnan, Guangdong, Xizang), Japan (Honshu, Kyushu), Bonin Is, Korea, West Malaysia, Indonesia, Myanmar, India, Iran, Pakistan, Sri Lanka, Taiwan, Algeria, Côte d'Ivoire, Egypt, Uganda, France, former Czechoslovakia (under glass), former USSR (South European Territory, Transcaucasus), USA (Louisiana, New Jersey, New York under glass), Cuba, and possibly Samoa and Fiji on the leaf sheaths and stems of Arundinaria, Bambusa, Miscanthus, Phyllostachys, Sasa and other bamboos (Foldi, 2001; Tao, 1999; Wong et al., 1999; Danzig and Pellizzari, 1998; Ben-Dov, 1988; Williams and Watson, 1988; Nakahara, 1982; Kawai, 1980; Beardsley, 1966; The Natural History Museum collection, London, UK). Scale cover of adult female circular to elongate oval, 1.5-4.0 mm long, white with brown terminal exuviae; scale cover of male elongate oval, narrow, about 1.0 mm long (Ben-Dov, 1988). The first instar nymph was described and illustrated by Howell and Tippins, 1977. Pygidium of adult female ODSECRP.jpg ; colony ODOSECL1.jpg
Comments
The area of origin of Odonaspis ruthae is uncertain. It was described from Hawaii and has since been recorded from many tropical and temperate areas (Williams and Watson, 1988). It has not been recorded from most of Europe, or from much of Asia. The species is probably more widespread than indicated, and may be under-collected due to its cryptic lifestyle.
Europe: present, no further details (Gill, 1997)
Greece: present, no further details (Danzig and Pellizzari, 1998)
Portugal: present, no further details (Moreira, 1976)
Asia
Chagos Archipelago: present, no further details (Nakahara, 1982)
Israel: present, no further details (Berlinger and Barak, 1981; Danzig and Pellizzari, 1998)
Pakistan: present, no further details (Ben-Dov, 1988)
Southern Asia: present, no further details (Danzig and Pellizzari, 1998)
Sri Lanka: present, no further details (Nakahara, 1982)
Africa
Central Africa: present, no further details (Danzig and Pellizzari, 1998)
Egypt: present (Abou-Elkhair et al., 1994)
Ethiopia: present, no further details (Nakahara, 1982)
Kenya: present, no further details (Nakahara, 1982)
Madagascar: present, no further details (Nakahara, 1982)
Mauritius: present, no further details (Williams and Williams, 1988)
Réunion: present, no further details (Williams and Williams, 1988)
South Africa: present, no further details (Nakahara, 1982; Danzig and Pellizzari, 1998)
Tanzania: present, no further details (Ben-Dov, 1988)
Zimbabwe: present, no further details (Nakahara, 1982)
Western Hemisphere
Argentina: present, no further details (Nakahara, 1982)
Misiones: present, no further details (Claps et al., 2001a)
Tucumán: present, no further details (Claps et al., 2001a)
Bermuda: present (Nakahara, 1982; Hodgson and Hilburn, 1991)
Bolivia: present, no further details (Ben-Dov, 1988)
Brazil: present, no further details (Nakahara, 1982)
Bahia: present, no further details (Ben-Dov, 1988)
Guanabara: present, no further details (Silva et al., 1968)
Paraná: present, no further details (Ben-Dov, 1988)
Rio de Janeiro: present, no further details (Claps et al., 2001a)
Sao Paulo: present, no further details (Claps et al., 2001a)
Central America: present, no further details (Danzig and Pellizzari, 1998)
Chile: present, no further details (Nakahara, 1982)
Easter Island: present, no further details (Charlín, 1973; Claps et al., 2001a)
Tarapacá: present, no further details (Claps et al., 2001a)
Cuba: present, no further details (Nakahara, 1982)
Guadeloupe: present, no further details (Ben-Dov, 1988)
Mexico: present, no further details (Nakahara, 1982; Miller, 1996)
Panama: present, no further details (Ben-Dov, 1988)
Peru: present, no further details (Ben-Dov, 1988)
Puerto Rico: present, no further details (Nakahara, 1982)
St Croix: present, no further details (Nakahara, 1982)
USA
Alabama: present, no further details (Nakahara, 1982)
Arkansas: present, no further details (Nakahara, 1982)
Arizona: present, no further details (Nakahara, 1982)
California: very common in southern parts (Gill, 1997)
Florida: present, no further details (Nakahara, 1982)
Georgia: present, no further details (Nakahara, 1982)
Hawaii: present, no further details (Nakahara, 1981; Danzig and Pellizzari, 1998)
Kansas: present, no further details (Ben-Dov, 1988)
Louisiana: present, no further details (Nakahara, 1982)
Mississippi: present, no further details (Nakahara, 1982)
North Carolina: present, no further details (Ben-Dov, 1988)
South Carolina: present, no further details (Nakahara, 1982)
Texas: present, no further details (Nakahara, 1982)
Oceania
Australia: present, no further details (CSIRO, 2001)
New South Wales: present, no further details (Ben-Dov, 1988)
Queensland: present, no further details (Ben-Dov, 1988)
South Australia: present, no further details (Ben-Dov, 1988)
Western Australia: present, no further details (Ben-Dov, 1988)
Christmas I.: present, no further details (Nakahara, 1982)
Cook Is: present (Williams and Watson, 1988)
Kiribati: present (Williams and Watson, 1988)
New Caledonia: present, no further details (Nakahara, 1982)
Papua New Guinea: present (Williams and Watson, 1988)
Tahiti: present, no further details (Williams and Watson, 1988)
Tuvalu: present (Williams and Watson, 1988)
Vanuatu: present (Williams and Watson, 1988)