Rice grasshopper

The rice grasshopper, scientifically known as Oxya velox, belongs to the order Orthoptera and the family Acrididae.

Adult insects typically measure between 20 and 30 mm in length, possessing a slender body and powerful hind legs adapted for jumping.

Their coloration ranges from greenish-yellow to brownish, providing excellent camouflage within the dense foliage of rice plants.

A key diagnostic feature of this species is the presence of a distinct tubercle (spine) on the ventral side of the thorax between the front legs.

Females are generally larger than males and possess a specialized ovipositor designed for laying eggs in soil or organic debris.

Rice is the primary host for this pest, as it provides the essential nutrients and favorable habitat for all developmental stages of the insect.

When rice crops are unavailable, the grasshopper may feed on various wild grasses growing near the paddies or in field margins.

Significant damage occurs during the tillering and elongation phases, when the loss of leaf area directly impacts the plant's photosynthetic capacity.

The insects also feed on young inflorescences, potentially leading to poor grain filling and substantial reductions in final crop yield.

Severe infestations can result in the destruction of 10–15% of the total leaf surface, weakening the plants and increasing susceptibility to diseases.

The lifecycle of Oxya velox is closely linked to the water management and temperature conditions of rice-growing areas.

Nymph hatching typically begins in late spring, once temperatures remain consistently high enough to support insect development.

Multiple generations occur throughout the summer months, with population peaks often observed during the rapid growth phase of the rice plants.

Grasshopper activity is highly dependent on daily temperatures; they are most active during the sunny hours of the day.

As autumn approaches, adults lay eggs in the soil, which enter a state of diapause and remain dormant throughout the winter season.

The primary symptom of a rice grasshopper infestation is the presence of irregular, notched edges along the leaves of the rice plants.

The leaves often appear ragged or "chewed" at the margins, which is a clear indicator of grasshopper feeding activity.

• Presence of frass (excrement) on the leaf surfaces.
• Specific feeding patterns on tender young shoots.
• Direct observation of grasshoppers jumping when entering the field.
• Development of bare patches within the dense rice canopy.

If the infestation coincides with the heading stage, damage to the panicles becomes visible, often resulting in empty or partially eaten grains.

High levels of activity are usually accompanied by audible chirping, which can be easily identified in quiet, warm conditions.

Effective management begins with rigorous field sanitation and deep plowing after harvest to destroy egg pods buried in the soil.

Maintaining clean field borders by removing weeds reduces alternative host plants and limits the migration of grasshoppers into the rice crop.

Water level management in the paddies can be used to disrupt the development of nymphs, preventing them from reaching the adult stage.

When pest populations exceed economic thresholds, the application of registered contact or systemic insecticides is recommended.

Integrated pest management strategies often utilize natural predators and parasitoids to keep grasshopper populations below damaging levels.