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Orseolia oryzae (Wood-Mason, 1889) · formerly or also: Pachydiplosis oryzae
The rice gall midge is a tiny fly whose maggot crawls into the growing point of a rice tiller and turns it into a hollow, silvery tube, like an onion leaf, instead of a panicle. Each 'silver shoot' is a lost panicle. It is a pest of wet-season rice in South and Southeast Asia, and because it exists as several biotypes, resistant varieties must be matched to the local population. In Africa a related species, Orseolia oryzivora, causes the same damage.
The scientific name of Asian rice gall midge is Orseolia oryzae (Wood-Mason, 1889), in the order Diptera, family Cecidomyiidae.
Older or alternative scientific names: Pachydiplosis oryzae.
South and Southeast Asia (India, Bangladesh, Sri Lanka, Nepal, Myanmar, Thailand, Laos, Cambodia, Vietnam, Indonesia) and southern China. The African rice gall midge, Orseolia oryzivora, occurs in West, Central and East Africa.
| Region | Status |
|---|---|
| South Asia | Widespread; key wet-season pest in endemic districts |
| Southeast Asia | Present in several countries |
| East Asia | Southern China |
| Africa | Related species O. oryzivora |
Adults are fragile, mosquito-like midges about 3-4 mm long; females have a bright orange-red abdomen. Larvae are tiny pale maggots that live at the base of the growing point. Biotypes are distinguished by their reaction on differential rice varieties.
| Crop stage | What you see |
|---|---|
| Nursery | Silver shoots in seedlings: the central leaf replaced by a pale, hollow tube. |
| Tillering | Tubular galls ('silver shoots' or 'onion leaves') replacing the central leaf of affected tillers; plants produce extra tillers that may also be attacked. |
| Panicle initiation onward | No new galls form after panicle initiation; galled tillers bear no panicles, reducing yield. |
Females lay eggs on leaves near the ligule; the larva moves down to the growing point and induces the gall, feeding inside it until it pupates near the top of the gall. The adult emerges through the tip of the silver shoot. The pest survives the dry season on wild rice, grasses and volunteers and builds up with the rains.
| Stage | Duration | Notes |
|---|---|---|
| Egg | About 3-4 days | Laid singly or in small groups on leaves. |
| Larva (inside the gall) | About 15-20 days | Feeds at the growing point. |
| Pupa | About 2-8 days | Wriggles to the gall tip before the adult emerges. |
| Adult | About 2-3 days | Nocturnal; attracted to light. |
Activity peaks in the humid, cloudy conditions of the monsoon (about 25-30 °C and high humidity); dry weather suppresses it.
Several generations during the wet season, often 6-8 in endemic areas.
Cloudy, humid, rainy weather; late transplanting in the wet season; high nitrogen; grassy weeds and volunteers carrying the pest between crops; and susceptible varieties.
Thresholds are based on silver shoots per square metre in the nursery and early crop, and on the percentage of tillers with galls later; they are lower in endemic areas. Values differ by region.
| Crop | Threshold | Unit | Crop stage | Region | Source |
|---|---|---|---|---|---|
| Rice | 1 silver shoot per m² (nursery and, in endemic areas, the early crop); 5% affected tillers in non-endemic areas | silver shoots per m²; % of tillers | Nursery to pre-tillering | South Asia | Kerala Agricultural University rice pest management guidance (celkau) |
| Rice | 10% silver shoots | % of tillers with galls | Mid-tillering | South Asia | Kerala Agricultural University rice pest management guidance (celkau) |
Thresholds are local. They depend on crop price, control cost, variety and natural-enemy activity, so use the figure your local extension service publishes where one exists.
Each gall is a lost productive tiller; yield losses in endemic areas typically range from about 10% to 30%, and higher in epidemic years when late-planted crops are heavily attacked.
Control works best as a sequence: prevent, monitor, then act only when a threshold or a risk forecast says so, using the least disruptive option that works.
Nursery and early-crop treatments are used in endemic areas where registered; once galls have formed, treatment does not restore the tiller. What is registered differs by country and changes over time; follow the label and your local plant-protection authority.
| Scheme | Group | Mode of action | Notes |
|---|---|---|---|
| IRAC | 4A | Nicotinic acetylcholine receptor competitive modulators (neonicotinoids) | Nursery and early uses. |
| IRAC | 28 | Ryanodine receptor modulators (diamides) | Used in some programmes. |
Rice and wild rice; some grasses (for example Paspalum and Leersia species) host it or related gall midges between crops.
How to grow the crop well is the first line of defence. Laisha's free grow guides cover each crop from sowing to harvest:
Written by Laisha from the sources above, in its own words. This page is general reference, not a prescription: confirm identification locally and follow the label and your plant-protection authority.