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Rice stem borers are key group of insect pests damaging the rice crop. These are pale yellow coloured caterpillars that live in rice stems. There are five species of stem borers distributed throughout India. Among these, yellow stem borer, S. incertulas is the most widespread, dominant, monophagous and destructive. The other borers are pink stem borer, Sesamia inferens (Walker), white borer, Scirpophaga innotata (Walker), dark headed stem borer, Chilo polychrysus (Meyrick) and striped stem borer, Chilo suppressalis (Meyrick).

 

Yellow stem borer : Scirpophaga incertulas  (Walker)(Lepidoptera : Pyralidae)

Kannada name: Haladi Kanda Koraka

Vernacular name:              

Rice stem borers are key group of insect pests damaging the rice crop. These are pale yellow coloured caterpillars that live in rice stems.

Adult:

Female: Bright yellowish forewings with a distinct black spot at the centre and with brownish yellow tuft of hair at the tip of abdomen.

Male :   Pale whitish yellow and spots on the forewings are not conspicuous.

Larva:  Pale yellow with orange yellow head.

Pupa: Pale to dark brown enclosed in a silken cacoon.

Eggs: White, oval, flat laid in groups (60-100 eggs) covered with brownish hairs from the anal tuft of females.

Adult stem borer		Larva of yellow stem borer	Egg mass of yellow stem borer

Period of occurrence: 

• Seedling to Panicle Initiation stage.
• In Northern regions of India, this pest is active from April to October and hibernates from November to March as a full grown larva in rice stubble.
• The pupation starts sometimes in March and the emergence of moths begin in April.

Extent of yield loss: 30-95 %  

Damaging stage of the insect: Caterpillar

Factors favoring development:

• Late planting
• Stubbles remaining in the field

Nature of Damage:

• Caterpillars bore into the central shoot of seedlings and tillers leading to death of central shoot
•  Caterpillars bore at the base of earhead and cause chaffy earheads

Life cycle: 31 - 46 days

Symptoms of damage:

• At vegetative stage, the central leaf whorl does not unfold, turns brownish and dries out although the lower leaves remain green and healthy. The dried leaf can be easily pulled out. This characteristic damage is known as "Dead Heart"
• At reproductive stage, panicle turn whitish, erect with chaffy spikelets and can be easily pulled out, is known as "white ears" (Photo).

Dead heart symptom at vegetative stage	White ear symptom at reproductive stage	Yellow stem borer infested field

A. Preventive measures: Use of resistant cultivars : Ratna, Sasyasree, Vikas (DRR), IR 36, IR 32, IR 66 and  IR 77 (IRRI) Clean cultivation and destruction of stubbles Clipping of leaf tips of the seedlings at the time of transplanting Installation of  pheromone traps with 5 mg lure @ 8 traps per ha for pest or 20 traps per ha for direct control by mass trapping Setting up of light trap as these moths are highly phototrophic. B. Biological control: Egg parasitoid: Inundative release of egg parasitoid, Trichogramma japonicum Ashmead five to six times @ 1,00,000 adults per ha starting from 15 days after transplanting.    Two important egg predators are:   Meadow grasshoppers - Conocephalus longipennis (de Haan) (Orthoptera: Tettigoniidae); and Crickets, Metioche vittataicollis (Stal) (Orthoptera: Gryllidae) Larval and pupal parasitoids: Cotesia flavipes Cameron (Hymenoptera: Braconidae) Temelucha philippinensis (Ashmead) (Hymenoptera: Ichneumonidae) Stenobracon nicevillei (Bingham) (Hymenoptera: Braconidae) Bracon chinensis Szepligeti (Hymenoptera: Braconidae) Tropobracon schoenobii (Viereck) (Hymenoptera: Braconidae) Xanthopimpla stemmator (Thunberg) (Hymenoptera: Ichneumonidae) Tetrastichus ayyari Rohwer (Hymenoptera: Eulophidae) Important larval predators are: Lady beetles, Micraspis spp. (Coleoptera: Coccinellidae) Carabid beetles, Ophionea spp. (Coleoptera: Carabidae) Rove beetle, Paederus fuscipes Curtis (Coleoptera: Staphylinidae) Water bug, Microvelia douglasi atrolineata Bergroth (Hemiptera: Veliidae) Water bug, Mesovelia vittigera (Horvath) (Hemiptera: Mesoveliidae) Water bug, Limnogonus fossarum (F.) (Hemiptera: Gerridae) Ants (Hymenoptera: Formicidae) Adults: The important predators feed on adult stem borer Anthocorid bug - Euspudaeus sp., (Hemiptera: Anthocoridae), Wolf spider - Lycosa pseudoannulata (Boesenberg and Strand) (Araneae: Lycosidae) feed on nymphs of GLH , BPH and adults of stemborer Black drongo - Dicrurus adsimilis (Bechstein)(Dicruridae) Diseases: Beauveria, Cordyceps and Nomuraea are white fungi that infect stem borers. Important pathogens are: Beauveria bassiana (Balsamo) Vuillemin (Moniliales: Moniliaceae) Nomuraea rileyi (Farlow) Samson (Moniliales: Moniliaceae) Cordyceps sp. (Entomophthoraceae) Bacillus thuringiensis Berliner (Bacteria) An unidentified nuclear polyhedrosis virus C. Control measures : Chemical control: ETL : 5 - 10 % dead hearts or 1 egg mass / m2 or 1 adult moth / m2

Wolf spider:  Pardosa pseudoannulata

Recommended Insecticides

Sl. No.	Chemical Name	Trade Name	Dosage per l of water	Dosage for spray tank
				10 l	12 l	16 l
Liquid /Spray formulations (EC, SL, WP, WG, WDG, SC)
1.	Monocrotophos 36 WSC	Nuvacron, Monocil	1.5 ml	15 ml	18 ml	24 ml
2.	Chlorpyrifos 20 EC	Dursban, Chlorban	2.5 ml	25 ml	30 ml	40 ml
3.	Cartap 50 WP		1.0   g	10 g	12 g	16 g
	Quinalphos 25 EC		2.0 ml	20 ml	24 ml	32 ml
5.	Endosulfan 35 EC		2.0 ml	20 ml	24 ml	32 ml
8.	Acephate 50 WP	Starthane, Asataf	1.0 g	10 g	12 g	16 g
11.	Fipronil 5SC		1.0 ml	10 ml	12 g	16 g
Solid formulations (Granules)
1.	Chlorpyrifos 10 G
2.	Carbofuran 3 G	Furadon	Nursery : 33 kg/ha Main field : 25 kg/ha
3.	Cartap 4G
4.	Fipronil 0.3 G		Nursery : 33 kg/ha Main field : 25 kg/ha

Note : Chemical control of stem borers is often not economic. The caterpillars are only vulnerable stage to many of the foliar sprays in a short time between hatching from the egg and entering a stem. Systemic insecticides, which go inside the plant, are the only reliable form of chemical control for stem borers after the borers have entered the stem, but by then it is generally too late to save the rice stem anyway.