Photo 1. 'Whitehead' - a symptom caused by stem borers: the base of the panicle is damaged preventing it from emerging or, if already emerged, the grain is unfilled and white.
White rice borer; also known as the paddy stem borer.
Scirpophaga nivella; however, there are other Scirpophaga species and there has been confusion between them; e.g., Scirpophaga excerptalis is a pest of sugarcane, Scirpophoga incertulas, yellow stem borer, occurs on rice as does Scirpophaga innota, white rice stem borer. Some authors consider Scirpophaga nivella to be the sugarcane top borer, and a miner pest of rice. Additionally, in the introduction to Scirpophaga nivella, PaDIL states: "This species is the same moth as the Australian species, Scirpophaga chrysorrhoa..." These moths belong in the Crambidae.
Restricted. South and Southeast Asia, Oceania. It is recorded from Australia, Fiji, New Caledonia, and Papua New Guinea.
Rice, and species in the sedge family, Cyperaceae.
The larvae do the damage, similar to other rice borer species (see Fact Sheet nos. 409, 410, 411).
The young larvae bore into the leaf vein of a still folded leaf, making a series of holes across it - seen when the leaf is unfurled. They then tunnel through the internodes down to the growing point. The youngest, unrolled leaf, withers and dies as the larvae eat the young stem. The dead stems, known as 'deadhearts', can easily be pulled from the base of the plant. Later, damage to the panicles results: either they do not emerge or they emerge with white unfilled grain, a symptom known as 'whiteheads' (Photo 1). Frass and larvae may be seen inside the stems.
Eggs are laid in groups of 6-30, covered in scales and hairs, on the underside of the leaf near the main vein. The larvae are brownish-yellow, becoming whiter as they age (Photo 2). They have a reddish line (a blood vessel) along the back. Pupae are yellow in a silk cocoon. Adult females are pure white, whereas the forewings of males are yellowish-brown with four dark spots on each (Photos 3&4). Wingspans are about 30 mm. The anal tuft of the male is orange whereas that of the female is sometimes brownish. The moths are nocturnal and strong flyers.
Rice plants can compensate for any damage caused by stem borers up to the stage of maximum tillering; however, infestation during panicle initiation and flowering causes loss in yield. Nevertheless, the white stem borer is considered to be a minor pest of rice.
Look for deadhearts and whiteheads at the vegetative and flowering stages, respectively. Look for tiny holes in the stem, and dissect stems for frass, larvae and pupae.
Countries not yet infested by the pink stem borer should consider all likely pathways for entry, and apply quarantine measures accordingly. Many countries throughout Asia, Africa, the Americas and Oceania are at risk. Pathways of introduction are likely to be via produce contaminated by pieces of stem of the many hosts infested by larvae or pupae.
In general, there are many predators (e.g., grasshoppers, crickets, ladybird beetles) and parasitoids of stem borers. However, misidentifications of Scirpophaga species make it difficult to know which of several egg and larval parasitoids are associated with which host. The egg parasites, Trichogramma australicum and Trichogramma japonicum, are reported to have been released in Taiwan as part of a biological control program which included Scirpophaga nivella.
Scirpophaga nivella usually occurs with other rice stem borers, e.g., Chilo, (other) Scirpophaga and Sesamia species and is controlled by the same measures used to control them.
Modern rice varieties that are relatively thin-stemmed, short, high tillering, and early maturing, may result in less damage from this moth, and stem borers generally. This aspect is important as well-grown, vigorous crops can withstand 20% deadhearts and 10% whiteheads before yield is affected.
As the stem borer is thought to be a minor rice pest, chemical control is unlikely to be necessary. There is also the risk of destroying natueral enemies if it is used. If chemicals are needed:
AUTHOR Grahame Jackson
Information (and Photo 1) Rice Knowledge Bank. IRRI. (http://www.knowledgebank.irri.org/training/fact-sheets/pest-management/insects/item/stem-borer); and CABI Scirpopaga nivella (2019) Crop Protection Compendium. (www.cabi.org/cpc); and Khan ZR et al. (1991) World bibliography of rice stem borers 1794-1990. IRRI/ICIPE; and White rice borer (and Photos 2-4) Anderson S, Tran-Nguyen L (2012) White Rice Borer (Scirpophaga nivella). (Source: N. Sallam DAFF Biosecurity.) PaDIL - (http://www.padil.gov.au); and from Pathak MD, Khan ZR (1994) Insect Pests of Rice. IRRI/ICIPE. Photo 5 CBG Photography Group, Centre for Biodiversity Genomics. (http://v3.boldsystems.org/index.php/Taxbrowser_Taxonpage?taxid=271138). Photo 6 Anderson S, Tran-Nguyen L (2012) Gold-fringed Rice Borer (Chilo auricilius). PaDIL - (http://www.padil.gov.au)
Produced with support from the Australian Centre for International Agricultural Research under project HORT/2016/185: Responding to emerging pest and disease threats to horticulture in the Pacific islands, implemented by the University of Queensland and the Secretariat of the Pacific Community.
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