Question

List the major pests and diseases of rice and discuss shoot borer's damage and management.

Hint:

Remember: Rice shoot borer causes deadhearts in vegetative stage and whiteheads in reproductive stage. Integrated management combining resistant varieties, cultural practices, biological control, and need-based chemical application is most effective.

Answer 1

Step 1: Major pests of rice.
The major insect pests that attack rice crops include:

• Stem borers: Yellow stem borer, Striped stem borer, Pink stem borer
• Leaf feeders: Rice leaf folder, Rice hispa, Rice horned caterpillar
• Sucking pests: Brown planthopper, Green leafhopper, Rice earhead bug
• Root feeders: Rice root weevil, Rice root aphid
• Grain feeders: Rice weevil (in storage), Rice bug
• Others: Gall midge, Rice caseworm, Whorl maggot

Step 2: Major diseases of rice.
The common diseases affecting rice cultivation are:

• Fungal diseases: Blast, Sheath blight, Brown spot, False smut, Sheath rot
• Bacterial diseases: Bacterial leaf blight, Bacterial leaf streak
• Viral diseases: Rice tungro virus, Rice grassy stunt virus
• Nematode diseases: Root knot nematode, White tip nematode

Step 3: Introduction to rice shoot borer (Stem borer).
Rice shoot borer, commonly known as rice stem borer, is one of the most destructive pests of rice. The major species include Yellow stem borer (Scirpophaga incertulas) and Striped stem borer (Chilo suppressalis). It is widely distributed across all rice-growing regions and causes significant yield losses.
Step 4: Nature of damage caused by shoot borer.
The damage caused by rice shoot borer occurs at different growth stages:

• Vegetative stage damage:
  • Larvae bore into the stem and feed internally
  • Damage to the central shoot causes deadheart - the central leaf whorl dries up and does not unfold
  • Deadhearts are easily pulled out from the stem
  • Tillering is reduced, affecting plant growth
• Reproductive stage damage:
  • Larvae feed inside the stem near the panicle base
  • This results in whiteheads - panicles become empty, chaffy, and white in color
  • Affected panicles stand upright and do not produce grain
  • Severe infestation can cause 20-60% yield loss
• Other damage symptoms:
  • Presence of egg masses covered with buff-colored hairs on leaf tips
  • Exit holes on stems where larvae have emerged
  • Frass (insect excrement) visible inside the stem
  • Reduced tillering and stunted plant growth

Step 5: Integrated management of rice shoot borer.
Effective management combines cultural, mechanical, biological, and chemical methods:

• Cultural methods:
  • Use resistant varieties like IR-36, IR-64, TN-1
  • Early planting to escape peak pest incidence
  • Synchronized planting in a community to reduce pest buildup
  • Avoid close planting; maintain optimum spacing
  • Balanced fertilization - avoid excess nitrogen
  • Field sanitation - destroy stubbles and crop residues after harvest
  • Summer plowing to expose pupae to sunlight and predators
• Mechanical methods:
  • Collection and destruction of egg masses
  • Removal and destruction of deadhearts and whiteheads
  • Use of light traps to attract and kill adult moths
  • Installation of pheromone traps (4-5 traps per acre) for monitoring and mass trapping
• Biological methods:
  • Conservation of natural enemies like egg parasitoids (Trichogramma spp.), larval parasitoids, predators like spiders, ladybird beetles
  • Release of Trichogramma japonicum @ 50,000 per acre at 10-day intervals
  • Use of microbial pesticides like Bacillus thuringiensis
• Chemical methods:
  • Apply insecticides only when economic threshold level is reached (2 egg masses/m² or 5% deadhearts)
  • Recommended insecticides: Carbofuran 3G, Cartap hydrochloride, Chlorantraniliprole, Fipronil
  • Apply granules in standing water or spray during evening hours
  • Rotate insecticides to avoid resistance development