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Plantwise Technical Factsheet

African rice gall midge (Orseolia oryzivora)

Host plants / species affected
Oryza longistaminata (perennial wild rice)
Oryza sativa (rice)
List of symptoms/signs
Growing point  -  internal feeding; boring
Inflorescence  -  galls
Leaves  -  abnormal forms
Stems  -  witches broom
Symptoms
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.


Prevention and control

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

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:


Impact
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).

Related treatment support
Plantwise Factsheets for Farmers
Kamara, S. I.; Taylor, D. R.; Norman, J. E.; Gbonamou, M.; CABI, 2006, English language
 
Pest Management Decision Guides
CABI; CABI, 2016, English language
CABI; CABI, 2016, French language
Shamie, I. M. O.; Luseni, M. M.; Ngegba, P. M.; Koroma, M.; CABI, 2012, English language
Ekobu, M.; Otim, M.; Luswata, K.; CABI, 2014, English language
 
External factsheets
Integrated Pest Management Extension Guide, Ministry of Food and Agriculture, 2004, English language
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