Parapoynx stagnalis (rice case bearer)

The young P. stagnalis larva causes linear grazing of leaves. Later in development, portions of leaf are cut off and used to make a portable case for the larva; the cut near the tip of a leaf is symptomatic.

IPM to control P. stagnalis and other pests of rice was discussed by Wickramasinghe (1978).

Chemical control is most often used: synthetic pyrethroids (see Suresh et al., 1985) have been found to be effective. A comparison between different chemicals applied to eggs and larvae was given by Bandong and Litsinger (1981a, b).

Nuclear polyhedrosis virus was tested as a potential control agent (Devanesan and Jacob, 1980), but lost its virulence after a few days.

Different strains of rice show different degrees of resistance, but these have not generally been shown to be significant, although Rao and Padhi (1984) found that C62-10 was resistant. Increase of resistance in rice plants was induced by the application of chelated metal complexes. Although incidence of pests was considerably lower in treated plants, changes in plant composition were also noted (Premila and Dale, 1984).

P. stagnalis is one of the major pests of rice in suitable habitats in South-East Asia and parts of Africa and South America. In the Philippines, a grain yield loss of about 10% was recorded when 30% of rice leaves were cut by larvae, or 25% of their area was scraped, during the first month after transplanting (Heinrichs and Viajante, 1987). In Argentina, rice yield losses of up to 52% have been recorded (Trujillo, 1991). In Madhya Pradesh, India, P. stagnalis damaged 38 to 94% of leaves in rice fields and the combined infestation of this pest with the rice leaf folder (Cnaphalocrocis medinalis) caused an overall yield loss of 80% (Patel and Khatri, 2001).