SHOOT FLY OF SORGHUM : Identification, Damage symptoms & Control

Introduction

The sorghum shoot fly (Atherigona soccata) is a significant pest causing serious damage to young sorghum plants, especially in key growing regions such as Maharashtra, Karnataka, Andhra Pradesh, and Tamil Nadu. This pest mainly attacks seedlings within the first 30 days after emergence and is responsible for substantial yield losses. It thrives in conditions of moderate temperatures and high humidity, with late-sown crops being more vulnerable.

Identification

• Adult Fly: Small, greyish fly approximately 3–5 mm long, resembling a housefly but with a yellowish abdomen and brown patches. Adults rest on the undersides of sorghum leaves.
• Larva: The larva is a creamy-white maggot about 8–10 mm long that bores into the central shoot of the plant, feeding on the growing point.
• Pupa: The pupa is reddish-brown, about 8–10 mm long, found either inside the dead shoot or in the soil near the base of the plant.

Damage Symptoms

• The maggots bore into the central shoot, killing the growing point and the youngest leaf, causing a characteristic symptom called the "dead heart." This symptom manifests as the central leaf withering and dying.
• Damaged plants tend to produce side tillers, which results in uneven growth and reduced overall crop productivity.
• Severe infestation can lead to withered panicles and complete crop failure in extreme cases.

Biology and Seasonal Incidence

• Female flies lay elongated, cigar-shaped eggs singly on the lower side of leaves, parallel to the midrib, usually during the first to fourth week after seedling emergence.
• Eggs hatch within 1-2 days, and the larvae then crawl down to bore into the central shoot.
• Under favorable conditions—mainly rainy seasons with moderate temperature and high humidity—the shoot fly population surges, causing peak damage typically between July and September.
• Multiple generations can build up rapidly due to the pest’s high fecundity and short life cycle.

Integrated Pest Management (IPM)

Cultural Control

• Sow sorghum immediately after the onset of the monsoon to avoid peak fly activity.
• Use resistant or tolerant sorghum varieties such as CSH 15R, Co-1, Maldandi, Hagari, Swati, and ICSV 705.
• Increase seed rate to about 12.5 kg per hectare for a denser, healthier crop stand.
• Remove and destroy crop stubbles and residues immediately after harvest to disrupt the shoot fly’s life cycle.
• Practice crop rotation with non-host crops such as legumes and maize to reduce pest buildup.
• Avoid applying farmyard manure after plant emergence as it provides suitable oviposition sites for the fly.

Mechanical Control

• During thinning, pull out and destroy plants exhibiting the dead heart symptom to prevent further breeding.
• Deploy fish-meal traps or plastic traps baited with fishmeal at 12 traps per hectare to catch adult flies until the crop reaches 30 days of age.
• Sticky traps may also be used to monitor adult fly populations.

Biological Control

• Promote and release natural enemies such as egg parasitoids (Trichogramma chilonis, Neotrichoporoides nyemitawus) and predators including spiders, coccinellids, and lacewings.
• Use neem-based biopesticides (containing azadirachtin) such as neem oil and Neem Seed Kernel Extract (NSKE) to suppress fly populations without harming beneficial insects.

Chemical Control

• Treat seeds with systemic insecticides like thiamethoxam or imidacloprid before sowing to protect seedlings from early infestation.
• Soil application of granular insecticides such as carbofuran or phorate at planting can reduce larvae in the soil.
• Foliar sprays with insecticides such as cypermethrin or chlorantraniliprole may be applied at the 3 to 4 leaf stage if infestation levels exceed economic thresholds.
• Chemical interventions should be integrated carefully with cultural and biological methods to minimize environmental impact.

Agri-Input Sector Relevance

In the agri-input sector, promoting integrated pest management practices is crucial for sustainable sorghum production. Input packages that combine resistant seed varieties, biocontrol agents, eco-friendly insecticides, and effective mechanical methods can significantly reduce shoot fly damage. Such packages agree with sustainability goals and can enhance farmer productivity by minimizing input costs and environmental risks.

Summary

The sorghum shoot fly poses a major threat primarily at the seedling stage but can be effectively managed through a well-coordinated IPM approach comprising timely sowing, resistant varieties, mechanical and biological control methods, and judicious chemical use. Field vigilance, farmer awareness, and agri-input facilitation are key to minimizing losses from this pest.