Domain: Eukaryota

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Lepidoptera

Family: Crambidae

Genus: Chilo

Species: C. polychrysus

Binomial Name: Chilo polychrysus (Meyrick, 1932)

It is found in India, Malaysia, Thailand, Laos, Vietnam and Indonesia. It is an insect of Tropical Asia. Manila, Philippines. Stem borer is a native insect of Asia and is found in Bangladesh, Brunei, Cambodia, China, India, Indonesia, Laos, Malaysia, Myanmar, Pakistan, Papua New Guinea, the Philippines, Thailand and Vietnam.

Host Range
The main host plant of the stem borer is rice (Oryza sativa). Other hosts include maize (Zea mays), sugarcane (Saccharum officinarum), wheat (Triticum aestivum) and grasses (Poaceae spp.); the larvae mainly feed on Cyperaceae and Poaceae species by boring into the stem.

• Eggs:  White, round laid singly on the paddy leaves.
• Larva:  Green with roughened skin flattened dorsally and has a dark brown head with a pair of red horn like processed and two yellow processes in the anal end. It feeds on the leaves.
• Pupa: The pupa of M. leda ismene is dark green, smooth, and hangs from rice leaves by its anal extremity. Dark green chrysalis hangs from the leaf and is attached to the leaf blade by its anal extremity.
• Adults: The butterfly is dark brown with large wings having a few black and yellow eye-like markings one on each of the forewings and six ocellar spots on hind wings.
• Wet-season form: Forewing: apex subacute; termen slightly angulated just below apex, or straight. Upperside brown. Forewing with two large subapical black spots, each with a smaller spot outwardly of pure white inwardly bordered by a ferruginous interrupted lunule; costal margin narrowly pale. Hindwing with a dark, white-centred, fulvous-ringed ocellus subterminally in interspace two, and the apical ocellus, sometimes also others of the ocelli, on the underside, showing through.
  Underside paler, densely covered with transverse dark brown striae; a discal curved dark brown narrow band on forewing; a post-discal similar oblique band, followed by a series of ocelli: four on the forewing, that in interspace 8 the largest; six on the hindwing, the apical and subtornal the largest.
• Dry-season form: Forewing: apex obtuse and more or less falcate; termen posterior to falcation straight or sinuous. Upperside: ground colour similar to that in the wet-season form, the markings, especially the ferruginous lunules inwardly bordering the black sub-apical spots on forewing, larger, more extended below and above the black costa. Hindwing: the ocellus in interspace 2 absent, posteriorly replaced by three or four minute white subterminal spots.[3]
  Undersides vary in colour greatly. Antennae, head, thorax and abdomen in both seasonal forms brown or greyish brown: the antennae annulated with white, ochraceous at apex.[3]

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Resident butterflies are known to fight off visitors to the area during dusk hours.[5] This chase behaviour is elicited even by pebbles thrown nearby. Larvae of green horned caterpillars feed on leaf margins and leaf blades. The feeding damage causes removal of leaf tissues and veins. Melanitis leda flies at moderate speed, usually active at dawn and before dusk, rarely seen during the day except when feeling disturbed. Often seen flying to visit flowers and puddles.

The caterpillars feed on leaves of the host plant, and tend to rest lengthwise on the underside of a grass blade during pauses between feeds. The caterpillars are gregarious and often feed and rest together (in a neat row) on the leaf underside.

The eggs are laid in small clusters (clusters of 2, 3 and 6 have been observed) on the underside of a grass blade of the host plant. Each spherical egg (about 1mm in diameter) is pale translucent with a light yellowish green tinge. The surface appears to be smooth to the naked eyes.

The egg takes about 3 days to hatch. The young caterpillar nibbles away a portion of the eggshell to exit and then proceeds to devour the rest of the egg shell almost entirely. It has a cylindrical body in whitish colour, and an initial body length of about 3-3.1mm. The body is covered with dorso-lateral and lateral rows of black setae. At the posterior end, there is a pair of backward-pointing processes. Its dark colored head features a number of setae and has a pair of short and rounded horns and a few lateral protuberances. As a result of its leaf diet, the 1st instar caterpillar soon takes on a strong greenish undertone. The first instar lasts about 3 days with the body length increasing to about 6-6. 8mm. In the 2nd instar, the cephalic horns become proportionately longer, and the two anal processes longer and thus pronounced. The few lateral conical protuberances are no longer present. The body is yellowish green, and the head is mostly black except for a central green patch. The body is also adorned with numerous minute whitish tubercles, each with a single seta emanating from it. Thin, lateral white bands are also present. The 2nd instar lasts about 2-2.5 days with the body length reaching about 10-11mm.

The 3rd instar caterpillar resembles the previous instar closely. The head capsule is mostly black except for the basal areas around the mouth parts which are pale lime green. The cephalic horns are again proportionately longer. This stage takes about 2-2.5 days to complete with body length reaching about 18-19mm.

The 4th instar caterpillar again has proportionately longer cephalic horns which now take on a hinge of reddish brown in its coloration. Small, lateral, white patches could be seen in the head capsule of some specimens. Otherwise, the caterpillar bears strong resemblance to those in the early two instars. The 4th instar lasts about 3.5-4 days with body length reaching about 31-32mm.The next moult brings the caterpillar to its 5th and final instar. The body is yellowish to lime green with the head exhibiting remarkable variations in coloration and markings. The cephalic horns are usually red to reddish brown, with some being whitish on the backward side. The head proper could be black with greenish patches and white lateral patches, or entirely green with lateral whitish bands. In a period of about 4.5-5.5 days, the body grows to a maximum length of about 45-51mm.Toward the end of the 5th instar, the body gradually shrinks in length and turns mostly yellowish green. Typically, the caterpillar will seek out a spot on the underside of a leaf blade to spin a silk pad. It then anchors itself there via its anal end, and assumes its upside-down pre-pupatory pose.Toward the end of the 5th instar, the body gradually shrinks in length and turn mostly yellowish green. Typically, the caterpillar will seek out a spot on the underside of a leaf blade to spin a silk pad. It then anchors itself there via its anal end, and assumes its upside-down pre-pupatory pose. After about one day as a pre-pupa, pupation takes place. The smooth pupa is yellowish green throughout. It is slightly angular in appearance, with a dorsal keel on the thorax and ridges defining the dorsal wing margins. There are a few dark stripes in the wing pads, otherwise the pupa bears no other markings. Length of pupae: 21-22mm.After 6 days of development, the pupa becomes darkened in color, and the ringed-spot on the forewings can now be seen through the pupal skin in the wing pads. The next day the eclosion event takes place with the adult butterfly emerging to start the next phase of its life cycle. In a nutshell: Melanitis leda reproduces by laying eggs (oviparous), female butterflies lay their eggs in small groups of 2, 3 or 6 eggs under the leaves of the host plant. The eggs are round, about 1 mm in diameter, pale translucent with a yellowish green tinge, the surface looks smooth. When the larvae hatch, they eat the egg shells to get out, after which they are consumed before consuming the first leaves. The butterfly lays round white eggs singly on the leaves. The caterpillar is green, slightly flattened with two red horn processes on the head and two yellow processes in the anal end. It pupates in a greenish chrysalis, which suspends from the leaf. The butterfly is dark brown with large wings having a black and yellow eye like spot one on each of the fore wings.

Manwan (1977) reported that C. polychrysus was a major pest of rice in Malaysia and parts of India and that its importance was increasingly recognized in some other countries. Khoo (1986) reported that C. polychrysus had ceased to be a major pest of rice in Peninsular Malaysia since the introduction of double-cropping with short-maturing varieties. Waterhouse (1993), in a review of the major arthropod pests of agriculture in South-East Asia, ranks C. polychrysus as widespread and important in Cambodia and the Philippines (but see under Notes on Taxonomy and Nomenclature) and important locally in Thailand, Laos, Vietnam, Malaysia and Indonesia. C. polychrysus is certainly less widespread and less important than C. suppressalis (Walker).

1. As with other stem borers of rice, the main symptoms caused by C. polychrysus are the appearance of ‘dead hearts’ and ‘white heads’ in growing crops, confirmed by dissection of samples of stems to retrieve larvae and pupae and rear adults for identification by specialist taxonomists. Stem borer caterpillars damage plant growing points and cause “dead hearts” (the youngest still unfolded leaves wilt and die), “white heads” (empty or partially filled heads of discoloured grain) and broken stalks in infested rice crops.
2. Tunnels inside the plant stems allow other pests and diseases into the infested stalks which can increase crop losses. Infested rice stalks are easily broken by the wind.
3. Rice stem borers, including stem borers, are the main insect pests of rice in Asia. These pests damage 5-10% of the annual Asian rice crop, causing 80% yield losses in heavily infested crops.

1. Plants/Growing point/dead heart
2. Plants/Growing point/dwarfing; stunting
3. Plants/Growing point/internal feeding; boring
4. Plants/Leaves/abnormal forms
5. Plants/Leaves/external feeding
6. Plants/Leaves/internal feeding
7. Plants/Stems/dead heart
8. Plants/Stems/internal feeding
9. Plants/Stems/stunting or rosetting
10. Plants/Whole plant/dead heart

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• Practice “Come clean, Go clean”
• Ensure all staff and visitors are instructed in and adhere to your business management hygiene requirements
• Source propagation material of a known high health status from reputable suppliers
• Monitor your crop regularly
• Keep records
• Control measures used against this species on rice are similar to those used against Chilo suppressalis, which is usually more important, and against other borer species.

• If direct seeding: sowing rate of 15-20 kg/rai.
• Plant early harvest rice varieties e.g. RD43.
• Pre-planting: plough soil and stubble, flooding the filed for 1 month to damage pupae.
• Fertilizer rates: Nitrogen (46-0-0) not over 10 kg/rai. (16-20-0) not over 30 kg/rai.
• Control Baryard grass (Echinochloa crus-galli), an alternative host.
• In Peninsular Malaysia, where C. polychrysus was a major pest before 1960, the introduction of double-cropping with short-maturing rice varieties has reduced its importance (Khoo, 1986).

The ability of antioxidants by FRAP showed that substances are capable of reducing Fe3+ and most of C3, the ability to inhibit the growth of bacteria with the lowest MIC and MBC values and the ability to Chilo polychrysus (Meyrick) found that C1 and C2 showed LT50 at 24 h and 48 h (19.00 and 19.33). These particles should be developed as biological agents to reduce the use of chemicals that are harmful to humans and the environment [5].

• Fipronil is the most toxic and most effective insecticide to control C. polychrysus in glasshouses [4].
• Cabosulfan [2], IRAC 1A. WHO II; Indoxacarb, IRAC 22A. WHO II; Chlorantraniliprole, IRAC 28. WHO U.

Spray at larva stage if dead hearts present on more than 10-15% of the crop. Rotate chemicals to prevent resistance. Don’t apply granular insecticide, don’t mix insecticides, don’t use 36 chemicals in the RD list (will kill natural enemy and cause resistance)

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1. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/chaetocnema#:~:text=Chaetocnema%20basalis%20Baly%201877%3A%20310.&text=It%20is%20found%20in%20Asia,this%20genus%20reported%20as%20pests.
2. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/chaetocnema#:~:text=Chaetocnema%20basalis%20Baly%201877%3A%20310.&text=It%20is%20found%20in%20Asia,this%20genus%20reported%20as%20pests.

1. https://en.m.wikipedia.org/wiki/Chilo_polychrysus
2. https://plantwiseplusknowledgebank.org/doi/full/10.1079/pwkb.species.44561#tabular-1
3. https://www.dpi.nsw.gov.au/biosecurity/plant/insect-pests-and-plant-diseases/stem-borer
4. http://journalarticle.ukm.my/18864/
5. https://www.scirp.org/journal/paperinformation?paperid=126779
6. https://www.cabdirect.org/cabdirect/mobile/abstract/20097401946