Scientific name: Hydrellia philippina Ferino

Common name: Rice whorl maggot

Translucent larva of rice whorl maggot, Hydrellia philippina Ferino Feeding damage of rice whorl maggot with yellow spots, streaks, and deformations Stunted plants caused by feeding of whorl maggot Whorl maggot adult Single, banana-shaped, white eggs of whorl maggot Pupa of whorl maggot Elongated egg of whorl maggot

Taxonomy:

Economic importance

Reports about the economic importance of the whorl maggot are conflicting. Some suggest that infestation could lead to losses of 30%, whereas others claim that even when crops are severely damaged there is no reduction in yield. Recent investigations showed that the yield loss recorded artifacts or loopholes. Whorl maggot damage can be compensated by plant growth. Insecticide control is not recommended.

Geographical distribution

Bangladesh, Cambodia, India, Indonesia, Lao PDR, Malaysia, Philippines, Thailand, Vietnam.

Morphology

Egg
The eggs are whitish and elongate. They are banana-shaped with a hard shell as covering. A single egg measures 0.65-0.85 mm long and 0.15-0.20 mm wide.

Larva
Larvae of the rice whorl maggot are legless. Newly hatched larvae are transparent to light cream. Mature larvae are yellowish. A mature larva is cylindrical with a pair of pointed spiracles found posteriorly. It is 4.4-6.4 mm long and 0.5-0.7 mm wide.

Pupa
The pupa is dark brown and subcylindrical. Its posterior end is tapering and has two terminal respiratory spines. The pupa is 4.8 mm long.

Adult
The gray adults have transparent wings. They have a silvery white frons and cheeks. Their antennae are dark gray with a silvery tinge in the inner portion of the second segment and 7-10 aristal hairs. They have a grayish mesonotum with silvery white and brown tinges, whereas their scutellum is silvery white to gray. Their abdomen is silvery white to gray with blackish brown in the middle of the three basal segments. They have yellow legs except for the femora.

The females are usually bigger than the males and are 1.5-3.0 mm long.

Symptoms

Heavily damaged plants are stunted with few tillers. The leaves have white or transparent patches. They easily break from the wind. Slightly damaged leaves have pinholes.

Biology and ecology

H. philippina is a semi-aquatic whorl maggot. It is common in irrigated fields and feeds on the central whorl leaf of the vegetative stage of the rice plant. Direct-seeded fields and seedbeds are not preferred by H. philippina. The adults are active during the day and rest on rice leaves near the water. They prefer thick vegetation and are attracted to open standing water around seedbeds.

The female adult lays 20 individual eggs. Eggs are laid until 8 days. Individual eggs are laid on the leaf surface. They stick to the leaves because of a gluey substance secreted by the female. Egg incubation is 2-6 days. Neonate maggots feed on the unopened central leaves where larval development is completed in 10-12 days. Before pupation, the mature maggots leave the feeding site and pupate inside older tillers. Pupation is 5-10 days.

Host range

The rice whorl maggot’s primary host is rice. It also feeds on grasses such as Brachiaria sp., Cynodon sp., Echinochloa sp., Leersia sp., Leptochloa sp., Panicum sp., and wild rice.

Detection and inspection

The damage symptoms of the whorl maggot are visible as white or transparent patches and pinholes. At the maximum tillering stage, these symptoms usually disappear.

Management

Cultural control
Since research has shown that the whorl maggot does not cause economic losses, no control is needed.

Biological control
The eggs are parasitized by Opius sp., Tetrastichus sp., and Trichogramma sp., and preyed upon by Dolichopus sp., Medetera sp., and Syntormon sp. The adults are hosts to Lycosa pseudoannulata (Boesenberg & Strand), Neoscona theisi (Walckenaer), Ochthera brevitibialis de Meijere, and Oxyopes javanus (Thorell).

Chemical control
Insecticide control for whorl maggot damage is not recommended. Damage symptoms often disappear in the crop’s maximum tillering stage and are compensated by crops.

Selected references

Bandong JP, Litsinger JA. 1986. Oviposition of rice whorl maggot (RWM) in wet seedbeds. Int. Rice Res. Newsl. 11(1):16-17.

Barrion AT, Litsinger JA. 1986. Ephydrid flies (Diptera: Ephydridae) of rice in the Philippines. Int. Rice Res. Newsl. 11(4):29-30.

Barrion AT, Litsinger JA. 1994. Taxonomy of rice insect pests and their arthropod parasites and predators. In: Biology and management of rice insects. Manila (Philippines): International Rice Research Institute. p 13-362.

Pathak MD, Khan ZR. 1994. Insect pests of rice. Manila (Philippines): International Rice Research Institute. 89 p.

Reissig WH, Heinrichs EA, Litsinger JA, Moody K, Fiedler L, Mew TW, Barrion AT. 1986. Illustrated guide to integrated pest management in rice in tropical Asia. Manila (Philippines): International Rice Research Institute. 411 p.

Shepard BM, Barrion AT, Litsinger JA. 1995. Rice-feeding insects of tropical Asia. Manila (Philippines): International Rice Research Institute. 228 p.

Shepard BM, Justo HD Jr., Rubia EG, Estaño DB. 1990. Response of the rice plant to damage by the rice whorl maggot Hydrellia philippina Ferino (Diptera: Ephydridae). J. Plant Protect. Trop. 17(3):173-177.

Viajante VD, Heinrichs EA. 1986. Rice growth and yield as affected by the whorl maggot Hydrellia philippina Ferino (Diptera: Ephydridae). Crop Protect. 5(3):176-181.