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Whitehead or dead panicles at reproductive stage (IRRI)
Yellow stem borer (YSB), White stem borer (WSB), Striped stem borer (SSB), Gold-fringed stem borer, Dark-headed stem borer, Pink stem borer
Scirpophaga incertulas (Walker), S. innotata (Walker), Chilo suppressalis (Walker), C. auricilius Dudgeon, C. polychrysus (Meyrick), Sesamia inferens (Walker)
The young rice crop can be visually inspected for deadhearts in the vegetative stages and whiteheads in reproductive stages. Stems can be pulled and dissected for larvae and pupae for confirmation of stem borer damage.
Deadhearts and whiteheads symptoms may sometimes be confused with damages caused by rats, neck blast, and black bug diseases.
The yellow stem borer is a pest of deepwater rice. It is found in aquatic environments where there is continuous flooding. Second instar larvae enclose themselves in body leaf wrappings to make tubes and detach themselves from the leaf and falls onto the water surface. They attach themselves to the tiller and bore into the stem.
Striped stem borer is most abundant in temperate countries and in non-flooded areas. Their final instars remain dormant in temperate areas during winter.
The pink stem borer is found in upland rice, which is grown near sugarcane or related grasses. The presence of alternate hosts encourages the pink stem borer to develop, multiply and survive during winter or dry season. Unlike other species of stemborers, the pink Stem borer have bare eggs laid between the leaf sheath and the stem.
High nitrogenous field favors population buildup of the stem borers. Fields planted later favors more damage by the insect pest that have built up in fields that have been planted earlier. Stubble that remains in the field can harbor stem borer larvae and or pupae.
The female YSB moth has a pair of black spots at the middle of each whitish, light brown to yellowish forewing. It has a wingspan of 24-36 mm. Its abdomen is wide with tufts of yellowish hairs all over. The male, gray or light brown in color, is smaller and has two rows of black spots at the tip of the forewings. It has a wingspan of about 20-30 mm. Its abdomen is slender toward its anal end and is covered with thin hairs dorsally. The YSB pupa is pale green and measures about 12 mm long. It is enclosed in a white silk cocoon. Fresh cocoon is pale brown and turns dark brown with age. The first instar YSB larva is about 1.5 mm long with yellowish green body. A full-grown larva has brown head and prothoracic shield and measures 20 mm. The egg mass of YSB is covered with brownish hairs from the anal tufts of the female. Individual eggs of are white, oval, and flattened.
The male and female WSB moths are immaculately white. The male moth is smaller than the female. Both adults have a tuft of long hairs on the thorax. Its fresh pupa is whitish and soft-bodied and turns brown with age. The larva is whitish to light yellow and without body markings. A mature larva is 25 mm long. The egg mass of WSB is disc-shaped and is covered with hair. It measures 3.5 mm to 6 mm long.
The SSB adults are brownish yellow with silvery scales. It has a row of 7 or 8 small black dots on the terminal margin of each forewing. The pupa is reddish brown and it measures about 11 to 13.5 mm long. It has two ribbed crests on the pronotal margins. The head has two short horns. The last segment of the pupa has visible spines. Neonate larvae have large shiny brown or orange head. Their prothoracic shields have the same color as their head. Their body is light brown or pink. Five rows of brown or pale purple longitudinal stripes run the entire length of the body. The stripes are found dorsally and laterally. Mature larvae measure 20 to 25 mm long. Newly laid eggs are glistening white. They are disc-shaped. Mature eggs turn yellow. They are black when about to hatch.
The adult moth of the gold-fringed stem borer is straw to light brown with silvery specks on the discal cell of the forewings or near the apical one-fifth. Several black dots are also found at the tip of the forewings. The male is generally smaller than the female moth. The pupa is yellow-brown. It has two distinct bumps at the front of the head. The larva has a black head. Five pinkish longitudinal stripes run along the entire length of the body. Newly laid eggs are white and are scale-like in appearance. They turn pale yellow to brown with age. Mature eggs that are about to hatch turn blackish.
Dark-headed stem borer adult is brownish yellow. It has dark markings of silvery scales or 6-7 tiny black dots on the center of the forewings. The hindwing has a lighter color. The female adult is larger than the male. The pupa is yellowish brown or light brown with remnants of abdominal stripes. It has sharp spines on the cremaster at the end of the abdomen. Neonate larvae are grayish white with a large head. The head and prothoracic shield are both black. It has a dirty white body with five longitudinal stripes of grayish violet or purplish brown passing through the entire larval body. The freshly deposited egg mass is glistening white. Individual egg is flat and scale-like. It measures 0.6 mm long and 0.4 mm wide. It turns yellowish and becomes black when about to hatch.
Pink stem borer adult is bright pale brown with some scattered dark brown markings. A purplish red band radiates from the central point in the forewing to the wing tip. Light stripes border the wing apex. The hindwings are whitish with light yellow scales along the major veins. The male moth is slightly smaller than the female and has a pectinate antenna. The female has a filiform type of antenna. The pupa is brown to dark brown with a tinge of bluish powdery substance. The male pupa is 12.0 mm long and the female measures 18.0 mm long. Neonate larva is white with a yellowish tinge and a black head capsule and prothoracic plate. With age, it turns pinkish purple with a brown or orange-red head capsule. Its body has no longitudinal stripes. The larva is 25.0 to 35.0 mm long. Freshly laid eggs are creamy white. They are nearly spherical or bead-like and measures 0.5 × 0.4 mm long. A one-day old egg is light yellow while a mature egg turns pink and black.
The yellow stem borer is monophagous to rice.
The white stem borer feeds primarily on rice. Its secondary host includes grasses like Cynodon dactylon (L.C. Rich) Pers., and Oryza australiensis Domin. and sedges Cyperus rotundus L., and Cyperus sp.
Rice is the main host of the striped stem borer. It also feeds on Brassica campestris L., Coix lachryma-jobi L., C. l. var. aquatica Roxb., Coix sp., L., Colocasia antiquorum Schott, Cyperus digitatus Roxb., Echinochloa colona (L.) Link, E. crus-galli (L.) P. Beauv. var. cruspavanis, E. crus-galli (L.) P. Beauv., Echinochloa sp., Eleusine indica (L.) Gaertn., Eriochloa procera (Retz.) C.E. Hubb., Ischaemum rugosum Salisb., I. timorense Kunth, Lycopersicon lycopersicum (L.) Karsten, Miscanthus sinensis Anderss., Oryza latifolia Desv., O. minuta J.C. Presl ex C.B. Presl, O. ridleyi Hook. f., Panicum auritum Presl ex Nees, P. miliaceum L., P. repens L., Paspalum punctatum Burm., P. scrobiculatum L., Pennisetum glaucum (L.) R. Br., Phragmites australis (Cav.) Trin., P. karka (Retz.) Trin., Pleiblastus simoni (Carr.) Nakai, Polygonum reynoutria Makino, Raphanus sativus L. var. acanthiformis, Saccharum arundinaceum Retz., S. fuscum Roxb., S. officinarum L., Sacciolepis myosuroides Ridl., Scirpus grossus L. f., Setaria gracilis H.B.K., S. pumila (Poir.) Roem. & Schult., Solanum melongena L., Sorghum bicolor (L.) Moench, Triticum vulgare Villars, Typha latifolia L, Vetiveria odorata Virey, Zea mays L., Zizania aquatica L., and Z. latifolia Turcz.
The rice plant is the primary host of the gold-fringed stem borer. It also feeds on Hemarthria compressa (L.f.) R. Br., Oryza latifolia Desv., Saccharum arundinaceum Retz., S. fuscum Roxb., S. officinarum L., S. spontaneum, Sacciolepis myosuroides (R. Br.) A. Camus, S. myurus (Lam.) A. Chase, Setaria pumila (Poir.), Sorghum bicolor (L.) Moench, S. halepense (L.) Pers., and Zea mays L.
The host plant range of the dark-headed stem borer in Malaysia are: Brachiaria distachya (L.) Stapf, Coelorachis glandulosa (Trin.), Cyperus ditatus Roxb., Echinochloa colona (L.) Link, Eleusine coracana (L.) Gaertn., E. indica (L.) Gaertn., Eriochloa procera (Retz.) C.E. Hubb., Hymenachne acutigluma (Steud.) Gilliland, Ischaemum timorense Kunth, Oryza sativa latifolia Desv., O. minuta J.C. Presl, Panicum auritum Presl ex Nees, P. repens L., Paspalum punctatum Burm., P. scrobiculatum L., Pennisetum purpureum K. Schum, Saccharum officinarum L., Saccharum sp., Sacciollepis myosuroides (R. Br.) A. Camus, S. myurus (Lam.) A. Chase, Sacciolepis sp., Setaria gracilis H.B.K., S. pumila (Poir.) Roem, and Schult., and Vetiveria odorata Virey. In India, Echinochloa crus-galli (L.) P. Beauv. is its alternate host. Oxya rufipogon Griff. and Saccharum officinarum L. are alternate hosts in Bangladesh. Setaria italica (L.) P. Beauv. is a recorded host in Bangladesh, India, and Malaysia.
Aside from the rice plant, other hosts of the pink stem borer include Andropogon schoenanthus L. (lemon grass), Avena sativa L. (oat), Beckmannia erucaeformis (L.) Hochst. (minogome), Calamagrotis epigejos Roth,Coelorachis glandulosa (Trin.) Stapf ex Ridl., Coelorachis sp., Coix lachryma-jobi L. (Job’s tears), Cymbopogon nardus (L.) Rendle, Cyperus digitatus Roxb., C. japonicus Makino (sedge), C. rotundus L. (coco grass, nutgrass), Cyperus sp., Echinochloa colona (L.) Link (jungle grass, jungle rice), E. crus-galli (L.) P. Beauv. (barnyard grass), E. frumentacea Link (sema), Echinochloa sp., E. stagnina (Retz.) P. Beauv., Eleusine stagnina (Retz.) P. Beauv., E. coracana (L.) Gaertn. (finger millet, ragi), E. indica (L.) Gaertn. (goose grass), Eleusine sp., Eragrostis cilianensis (All.), Eragrostis sp., Erianthus arundinaceus (Retz.) Jesw., Erianthus sp., Eriochloa procera (Retz.),E. villosa (Thum.) Kunth, Hemarthria compressa (L.f.) R.Br. (jove grass), Hordeum sativum Jess. (barley), Hymenachne myurus (Lam.) Beauv., Hymenachne sp.,Ischaemum rugosum Salisb., Ischaemum sp., I. timorense Kunth, Miscanthus sinensis Anderss., Miscanthus sp., O. latifolia Desv.,Oryza minuta J.C. Presl ex C.B. Presl, Panicum auritum Presl, P. maximum Jacq. (guinea grass), P. miliaceum L. (porso or brown corn millet), P. repens L. (torpedo grass, panic rampant), Panicum sp., Paspalum punctatum Burm., P. scrobiculatum L. (kodo millet, kodra millet), Paspalum sp., P. thunbergii Kunth ex Steud., Pennisetum glaucum (L.) R. Br. (pearl millet, bulrush millet), Pennisetum sp., Phragmites karka (Retz.) Trin. Ex Steud. (millet), Phragmites sp., Polypogon fugax monospeliensis (L.), Polypogon sp., Rumex crispus L., Rumex sp. (giant lobelias), Saccharum arundinaceum Retz. (kanra), Saccharum arundinaceum var. ciliaris (sar), S. fuscum Roxb. (ikri), S. officinarum L. (sugarcane), Saccharum sp., S. spontaneum L. (wild sugarcane),Sacciolepis myosuroides (R. Br.) A. Camus, S. myurus (Lam.) A. Chase, Sacciolepis sp., Scirpus grossus L.f., S. lacustris L., S. maritimus L., Scirpus sp., Setaria italica (L.) P. Beauv. (Italian millet, foxtail millet, Indian millet), S. pumila (Poir.) Roem. and Schult.,Setaria sp., Sorghum bicolor (L.) Moench (sorghum), S. halepense (L.) Pers. (Johnson grass),S. sudanense (Piper) Stapf, Teosinte sp., Triticum aestivum L. (wheat), Triticum sp. (wheat), Vetiveria odorata Virey, Zea mays L. (maize), Zea sp., and Zizania latifolia (Griseb.).
Stemborers feed on the crop during the vegetative and reproductive stages of the rice plant. Excessive boring through the sheath can destroy the crop. Its damage caused reduction in the number of reproductive tillers.
The stem borer larvae bore at the base of the plants during the vegetative stage. On older plants, they bore through the upper nodes and feed toward the base. Late infestation causes whiteheads.
The yellow stem borer is an important pest of irrigated rice in South and Southeast Asia. In the Philippines, it caused about 5% to 10% yield loss. About 1% to 19% yield loss in early planted rice crops and 38% to 80% yield in late-planted rice were reported in India.
The white stem borer (WSB) is an important pest in rainfed wetland rice. In West Java, Indonesia, this pest has been observed in irrigated rice fields. WSB causes occasional outbreaks, especially in the Indramayu and Cirebon areas. Along the northern portion of West Java, an outbreak occurred and destroyed 15,000 ha of rice fields during the wet season of 1989-90.
The striped stem borer is one of the most important insect pests in temperate Asia. During the vegetative stage, larval feeding causes deadheart. The rice plant can compensate by growing new tillers. At the reproductive stage, feeding causes whitehead. The damage could reach 100%.
The gold-fringed stem borer is a major pest of sugarcane in India and Taiwan. It is a pest of maize and upland rice. Yield losses of 30% and 20% due to this insect were reported in India and Bangladesh, respectively
Among the stem borers, the dark-headed and the pink stem borer are less important. The pink stem borer is polyphagous and prefers sugarcane to rice.
Stem borers can be managed using cultural control measures, biological control agents, the use of resistant varieties, and chemical control.
Cultural control measures include proper timing of planting and synchronous planting. The crops should be harvested at ground level to remove the larvae in stubble. Likewise, stubble and volunteer rice should be removed and destroyed. Plowing and flooding the field can kill larvae and pupae in the stubbles. At seedbed and transplanting, egg masses should be handpicked and destroyed. The level of irrigation water can be raised periodically to submerge the eggs deposited on the lower parts of the plant. Before transplanting, the leaf-top can be cut to reduce carry-over of eggs from the seedbed to the field. Application of nitrogen fertilizer should be split following the recommended rate and time of application.
Biological control agents include braconid, eulophid, mymarid, scelionid, chalcid, pteromalid and trichogrammatid wasps that parasitize the eggs of yellow stem borer. Ants, lady beetles, staphylinid beetles, gryllid, green meadow grasshopper, and mirid bug also eat eggs. The larvae are parasitized by phorid and platystomatid flies, bethylid, braconid, elasmid, eulophid, eurytomid and ichneumonid wasps. They are attacked by carabid and lady bird beetles, chloropid fly, gerrid and pentatomid bugs, ants, and mites. Bacteria and fungi also infect the larvae. A mermithid nematode also attacks the larvae. Chalcid, elasmid and eulophid wasps parasitize the pupae. Ants and earwigs also eat the pupa. Bird, asilid fly, vespid wasp, dragonflies, damselflies, and spiders prey upon the adults.
There are varieties from IRRI with resistance to the stem borers.
JLA Catindig and KL Heong