Orseolia oryzivora
(African rice gall midge)

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Identity

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Preferred Scientific Name

• Orseolia oryzivora Harris & Gagné, 1982

Preferred Common Name

• African rice gall midge

Local Common Names

• West Africa: cécidomyie du riz

EPPO code

• ORSEOV (Orseolia oryzivora)

Taxonomic Tree

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• Domain: Eukaryota
•     Kingdom: Metazoa
•         Phylum: Arthropoda
•             Subphylum: Uniramia
•                 Class: Insecta
•                     Order: Diptera
•                         Family: Cecidomyiidae
•                             Genus: Orseolia
•                                 Species: Orseolia oryzivora

Notes on Taxonomy and Nomenclature

Top of page This species was described by Harris and Gagné (1982) who recognized that it is morphologically distinct from the Asian rice gall midge, Orseolia oryzae. Before that date it had been incorrectly assumed that O. oryzae occurred in Africa as well as Asia. Earlier records of that species in Africa are now known to relate to O. oryzivora. All known species of Orseolia induce galls in Poaceae (Gramineae). Most species have been described from Asia, and Gagné (1985) published a taxonomic revision of the 21 species known in south-east Asia.

Description

Top of page Illustrated technical descriptions of adults, larvae and pupae of this species are given in Harris and Gagné (1982), which should be consulted for diagnostic details. A brief data sheet published by IRAT-CIRAD (Betbeder-Matibet, 1990) contains colour photographs of an adult female, a pupa and a pupal case.

Eggs

Eggs are elongate cylindrical, about 0.5 mm long, initially white but orange-yellow just before hatching.

Larvae

All larval stages lack jointed legs or other obvious appendages and are relatively featureless with small heads which partially retract into the anterior segments of the thorax. As far as is known, there are three larval instars. Body colour varies from white to pink. Full-grown final instar larvae are up to 5 mm long and have a median ventral sternal spatula on the first thoracic segment.

Pupae

Pupae are 5-7 mm long and female pupae are generally larger than males. The antennal horns taper to a single point and the abdominal tergites bear series of spines. See Harris and Gagné (1982) for further details, including SEMs of diagnostic characters.

Adults

Adults are small reddish-brown midges with a wing length of about 3.0-3.5 mm in males and about 3.5-4.0 mm in females. Both sexes have long antennae composed of 12 flagellomeres which, in males, have three sets of linked filiform sensoria (circumfila). The male terminalia form a bilaterally symmetrical clasper and the female ovipositor is non-retractile with a pair of distal cerci. Diagnostic characters are described and illustrated in Harris and Gagné (1982).

Distribution

Top of page Published records of this species were mapped by the Commonwealth Institute of Entomology (CIE, 1984) and some new country records have been added since that date. It seems probable that this species occurs in suitable habitats throughout sub-Saharan tropical Africa but may often be at low population levels that are difficult to detect.

O. orzivora has also been reported in Guinea, Sierra Leone and Tanzania (K Harris, c/o CABI Biosciences Division, Silwood Park, Ascot, UK, unpublished data).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 10 Jan 2020

Risk of Introduction

Top of page Transfer of live eggs, larvae and pupae on infested plants is possible, especially on seedlings for transplanting. There is therefore some risk that this pest could be accidentally moved into uninfested areas.

Habitat

Top of page Most records of this species are from relatively low-lying river flood plains and areas of irrigated rice in tropical sub-Saharan Africa.

Hosts/Species Affected

Top of page Field surveys and host-transfer experiments in West Africa have shown that this species can only develop on cultivated and wild species of Oryza ( C Williams, c/o CABI Biosciences Division, Silwood Park, Ascot, UK, unpublished data). In many areas the cultivated crop is the main host throughout the year but in the savannah zone the presence of the wild perennial grass, O. longistaminata, is probably essential for dry season survival. A distinct species of Orseolia occurs on Paspalum (K Harris, c/o CABI Biosciences Division, Silwood Park, Ascot, UK, unpublished data).

Host Plants and Other Plants Affected

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Growth Stages

Top of page Flowering stage, Vegetative growing stage

Symptoms

Top of page The most obvious field symptom is the presence in cultivated rice of long cylindrical galls, about 3 mm in diameter and from a few cm up to 1-1.5 m long. They are often silvery white and are generally known as 'silver shoots' or 'onion leaf galls'. At low levels of infestation, galls may be difficult to detect but severe infestations cause marked reductions in the numbers of inflorescences and consequently in grain yields. Careful examination of the fully formed galls may reveal the presence of gall midge larvae and pupae inside, or (if adults have already emerged), the pupal cases attached to emergence holes near the tips of the galls. Galled plants may tiller profusely to compensate for loss of growing points.

List of Symptoms/Signs

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Biology and Ecology

Top of page The main published accounts of the biology and ecology of this species are those of Bouchard et al. (1992) for Burkina Faso and Umeh and Joshi (1993) for Nigeria. Additional information is available from recent work in West Africa undertaken during a WARDA/CAB International funded research project, results of which will be published soon.

Female rice gall midges lay eggs on the inner or outer surfaces of a leaf sheath, just below the ligules, or on the upper or undersides of leaf blades of young rice plants, either singly or in groups of 3-5 eggs. Each mated female lays up to 400 eggs during a 3-day life span. Eggs hatch about 3 days after laying and first instar larvae move to the growing points where they feed for 2-3 weeks. Larval feeding induces development of the gall which is short and inconspicuous until larvae are ready to pupate. The gall then elongates and the pupa works its way up the gall and abrades an emergence hole through which it protrudes when the adult emerges. Each gall contains a single larva and galls generally appear about 20-40 days after the crop has been transplanted.

Observations on this species reared in cages in Burkina Faso (Bouchard et al., 1992) indicated that development from egg to adult took 23-36 days at 27°C and that adult emergence continued for 10 days, with maximum emergence at 3-6 days. Males and females emerged at about the same time and the sex ratio of reared male to female adults was 1:2.

In south east Nigeria, Umeh and Joshi (1993) recorded that adults appeared in light traps during the third week of June in 1991 and peak emergence occurred 8 weeks later.

In Malawi, Feijen and Schulten (1983) recorded that the life cycle from egg to adult was not more than a month and that under favourable conditions it might be much shorter. They also suggested that up to nine successive adult generations developed during the 1973-1974 rainy season.

Natural enemies

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Notes on Natural Enemies

Top of page Two hymenopterous parasitoids, Aprostocetus procerae [= Tetrastichus pachydiplosisae] and Platygaster diplosisae are widespread and relatively common and are the best known natural enemies of this pest. Feijen and Schulten (1983) studied an outbreak in Malawi in 1973-1975 in which A. procerae parasitized 80% of larvae and pupae once the main midge attack had developed and, to a large extent, controlled the pest. They observed that the larva of A. procerae was an ectoparasite, feeding on larvae and pupae within galls, and that there was usually only one parasitoid per host. They also provided a detailed description of the parasitoid.

In Burkina Faso, Dakouo et al. (1988) observed both parasitoid species and noted that they provided an important check to pest populations with up to 77% of larvae parasitized late in the season.

In south east Nigeria, Umeh and Joshi (1993) monitored seasonal development of these two species during the 1991 growing season and recorded that P. diplosisae appeared first, followed 3 weeks later by A. procerae. Subsequently, parasitism by the two parasitoids increased steadily and reached 98% by the 28th week. Galls parasitized by P. diplosisae were shorter and thicker than unparasitized galls but no differences were apparent in galls parasitized by A. procerae, which generally attacked pupae by ovipositing through the gall.

The widespread occurrence of both parasitoids in West Africa and their effects on midge populations have since been confirmed by Williams (c/o CABI Biosciences Division, Silwood Park, Ascot, UK, unpublished data).

Seedborne Aspects

Top of page This pest is not seedborne.

Plant Trade

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Plant parts not known to carry the pest in trade/transport
Bark
Bulbs/Tubers/Corms/Rhizomes
Flowers/Inflorescences/Cones/Calyx
Fruits (inc. pods)
Growing medium accompanying plants
Leaves
Roots
Stems (above ground)/Shoots/Trunks/Branches
True seeds (inc. grain)
Wood

Impact

Top of page Up to the mid 1970s the African rice gall midge was not a major pest, although there had been occasional local outbreaks, as in Cameroon in the mid-1950s (Descamp, 1956). Between 1971 and 1975, Feijen and Schulten (1983) studied an outbreak in Malawi and reported that it was only a minor pest, abundant in a prolonged season of heavy rain but with up to 100% parasitization of larvae by Aprostocetus procerae. In the late 1970s high losses were observed in Burkina Faso, but were not widely reported, which persisted into the 1980s (Dakouo et al., 1988). In 1984 this pest was also reported from all lowland irrigated rice areas in Zambia, with very high incidence at two sites (Alam et al., 1985).

In 1988 the situation changed dramatically when a major outbreak caused serious losses in the savanna zone of Nigeria, with 45 to 80% of all tillers infested in the most severely affected areas and consequent serious reduction of yields in some fields (Ukwungwu et al., 1989). By 1997 severe outbreaks, with tiller infestation of 20% or more, occurred regularly in several important rice growing areas of Nigeria, Burkina Faso and Mali and the midge was considered a key pest of lowland rice in those countries. Its pest status elsewhere in Africa was much less certain but conspicuous localized outbreaks had been reported from Mali, western Sierra Leone, Guinea, Guinea Bissau, northern Ghana, southern Chad and at rice irrigation schemes in Tanzania and Uganda (C Williams, c/o CABI Biosciences Division, Silwood Park, Ascot, UK, unpublished data).

In Burkina Faso, cage experiments on yield losses resulting from artificial infestations indicated that, although infestation induced some compensatory production of tillers, there was a significant negative correlation between yield and infestation with a 2% grain yield loss for each 1% tillers damaged (Nacro et al., 1996).

In eastern Nigeria, trials at 47 rain-fed lowland farm sites in 1995 provided detailed and consistent yield loss data for natural infestations. Regression analysis indicated incremental yield losses of 2.3 to 3.1% for each increase of 1% tillers with galls at 7 to 9 weeks after transplanting, over the range 0-30% infestation. Similar research station trials on irrigated rice, using artificial infestation, indicated lower levels of yield loss, probably because midge attack was less prolonged and agronomic conditions were more favourable than on farmers' fields (C Williams, c/o CABI Biosciences Division, Silwood Park, Ascot, UK, unpublished data).

Diagnosis

Top of page Positive diagnosis requires examination of slide-mounted adults, larvae and pupae by high-power microscopy and reference to diagnostic descriptions published by Harris and Gagné (1982).

The genus Orseolia can be separated from other genera of Cecidomyiidae likely to be found in association with cultivated plants, as follows:

Female ovipositor non-retractile and with relatively large terminal cerci; male terminalia with undivided hypoproct, densely clothed in microtrichia; antennal formula 2+12 in both sexes; males flagellomeres trifiliar, with long necks and internodes and relatively short circumfiliar loops; female flagellomeres elongate cylindrical, with long necks and simple, linked circumfiliar.

Detection and Inspection

Top of page Examination of growing crops for typical symptoms is the main method of detection although visual inspection will not always give accurate assessments of infestation levels. Those are best obtained by random sampling and laboratory examination. In Nigeria, Ukwungwu and Joshi (1992) developed methods for extensive field surveys involving removal and dissection of samples of 30-50 galls taken from fields selected at random at intervals of about 5-30 km. More rigorous sampling techniques have since been developed based on quadrat sampling of crops and wild host grasses (C Williams, c/o CABI Biosciences Division, Silwood Park, Ascot, UK, unpublished).

Light-trapping is used to detect adult activity of the Asian rice gall midge and has been used by Umeh and Joshi (1993) to monitor seasonal fluctuations in adult activity in south east Nigeria.

Similarities to Other Species/Conditions

Top of page O. oryzivora is morphologically very similar to an undescribed species reared from Paspalum but the two species can be separated based on the morphological characters of the pupae.

Similar symptoms are caused by lepidopterous stem borers and by some diseases but these do not involve the production of galls.

Prevention and Control

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Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Introduction

The published literature on control methods is limited as little conclusive research has been completed since this species first became a major pest.

Integrated Pest Management

Plant breeding for resistance or tolerance to midge attack shows greatest promise at present. One Oryza sativa improved variety, 'Cisadane' has reasonably high yield potential and has shown tolerance to natural midge infestations in on-farm trials in Nigeria. In addition, an intensive screening programme in Nigeria has identified sources of resistance to heavy midge infestations in the indigenous African rice, Oryza glaberrima, and in several traditional African varieties of the exotic Oryza sativa. Screening, selection and breeding is co-ordinated by the West Africa Rice Development Association (WARDA) in conjunction with national programmes, especially at the National Cereals Research Institute (NCRI), Nigeria and the Institut National d'Études et de Recherches Agricola (INERA), Bobo-Dioulasso, Burkina Faso.

Other elements of integrated pest management are under investigation with the aim of providing a selection of mutually compatible management options from which farmers and local support services can select appropriate cost-effective measures for their particular circumstances. The main objectives are:

To find methods to reduce the abundance of alternative hosts outside the cropping season and so limit midge colonization of early planted rice crops.

To reduce the period during which rice crops are susceptible to midge infestation by synchronizing wet season planting of rice, so far as agronomic and socio-economic restraints permit.

To retard the rate of midge population increase within rice crops by the use of varietal resistance/tolerance, the enhancement of natural biological control or the use of appropriate chemical control.

Biological Control

A preliminary assessment of the potential for classical biological control has been made but no obvious candidate agents have been identified (Harris, Cock and Williams, c/o CABI Biosciences Division, Silwood Park, Ascot, UK, unpublished data). It may however be possible to enhance natural indigenous biological control by conservation and management of Aprostocetus procerae and Platygaster diplosisae (C Williams, c/o CABI Biosciences Division, Silwood Park, Ascot, UK, unpublished data).

Chemical Control

Trials in Nigeria reported that isazofos was as effective as diazinon in controlling midge infestation (Ukwungwu, 1990).

An alternative to field application of insecticides is treatment of young plants by immersion in insecticide to kill eggs and young larvae before transplanting (Betbeder-Matibet, 1990).

The potential danger of widespread and inappropriate use of insecticides against this pest is an important incentive for the speedy development of non-insecticidal methods of control.
 

References

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Alam MS, Zan K, Alluri K, 1985. Gall midge (GM) Orseolia oryzivora H & G in Zambia. International Rice Research Newsletter, 10(2):15-16

Betbeder-Matibet M, 1990. Insect pests of food crops in Africa and the Indian Ocean region. Montpellier, France; Centre de Cooperation Internationale en Recherche Agronomique pour le Developpement, Institut de Recherches Agronomiques Tropicales, 122 pp.

Bouchard D, Ouedraogo A, Boivin G, Amadou K, 1992. Mass rearing and life cycle of the African rice gall midge, Orseolia oryzivora H & G., in Burkina Faso. Tropical Pest Management, 38(4):450-452

CABI, 1984. Distribution Maps of Pests. Series A (Agricultural), Map no. 464 Orseolia oryzivora Harris & Gagné. Wallingford, UK: CAB International.

Dakouo D, Nacro S, 1987. Chemical control of rice gall midge (GM) Orseolia oryzivora. International Rice Research Newsletter, 12(3):38

Dakouo D, Nacro S, Sie M, 1988. Seasonal incidence of the rice gall midge, Orseolia oryzivora H. and G. (Diptera, Cecidomyiidae) in the south-west of Burkina Faso. Insect Science and its Application, 9(4):469-473

Descamps M, 1956. Deux dipteres nuisibles au riz dans le Nord Cameroun Pachydiplosis oryzae Wood Mason Pachylophus sp. aff. lugens Loew. Phytiatrie-Phytopharmicie, 5:109-116.

Feijen HR, Schulten GGM, 1983. Note on the African rice gall midge Orseolia oryzivora Harris & Gagne (Diptera, Cecidomyiidae), with a redescription of its parasitoid Tetrastichus pachydiplosisp Risbec (Hymenoptera, Eulophidae). Zeitschrift für Angewandte Entomologie, 96(5):509-520

Gagne RJ, 1985. A taxonomic revision of the Asian rice gall midge, Orseolia oryzae (Wood-Mason), and its relatives (Diptera: Cecidomyiidae). Entomography, 3:127-162

Harris KM, Gagne RJ, 1982. Description of the African rice gall midge, Orseolia oryzivora sp. n., with comparative notes on the Asian rice gall midge, O. oryzae (Wood-Mason) (Diptera: Cecidomyiidae). Bulletin of Entomological Research, 72(3):467-472

Nacro S, Heinrichs EA, Dakouo D, 1996. Estimation of rice yield losses due to the African rice gall midge, Orseolia oryzivora Harris and Gagne. International Journal of Pest Management, 42(4):331-334; 14 ref.

Taylor DR, Fomba SN, Fannah SJ, Bernard HM, 1995. African rice gall midge pest in Sierra Leone. International Rice Research Newsletter, 20, 27

Ukwungwu MN, 1990. Efficacy of granular isazofos against rice gall midge in Nigeria. Crop Protection, 9(4):252-254

Ukwungwu MN, Joshi RC, 1992. Distribution of the African rice gall midge, Orseolia oryzivora Harris and Gagne and its parasitoids in Nigeria. Tropical Pest Management, 38(3):241-244

Ukwungwu MN, Winslow MD, John VT, 1989. Severe outbreak of rice gall midge (GM) in the savannah zone, Nigeria. International Rice Research Newsletter, 14(4):36-37

Umeh EDN, Joshi RC, 1993. Aspects of the biology, ecology and natural biological control of the African rice gall midge, Orseolia oryzivora Harris and Gagne (Dipt., Cecidomyiidae) in south east Nigeria. Journal of Applied Entomology, 116(4):391-398

Distribution References

CABI, Undated. Compendium record. Wallingford, UK: CABI

CABI, Undated a. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI

Harris K M, Gagne R J, 1982. Description of the African rice gall midge, Orseolia oryzivora sp. n., with comparative notes on the Asian rice gall midge, O. oryzae (Wood-Mason) (Diptera: Cecidomyiidae). Bulletin of Entomological Research. 72 (3), 467-472. DOI:10.1017/S000748530001364X

Taylor DR, Fomba SN, Fannah SJ, Bernard HM, 1995. African rice gall midge pest in Sierra Leone. In: International Rice Research Newsletter, 20 27.

UK, CAB International, 1984. Orseolia oryzivora. [Distribution map]. In: Distribution Maps of Plant Pests, Wallingford, UK: CAB International. Map 464.

Distribution Maps

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