Measures to control Stem borer in Maize

In this blog, we will explore the critical steps for controlling stem borer in maize, from recognizing damage symptoms and identifying the pest to understanding favorable conditions and implementing effective management techniques.

What is Maize Stem Borer ?

Maize stem borer is a destructive pest that can cause significant damage to maize crops. The pest is identified by its yellowish-brown larva with a brown head, and as it matures, it turns into straw-colored moths. The damage begins with the young larva feeding on tender, folded leaves, leading to a "shot hole" appearance. As the larvae grow older, they bore into the stem, feeding on internal tissues, resulting in bore holes, tunneling, and eventually causing the central shoot to dry up, leading to a condition known as the "dead heart."

Overview of Maize Stem Borer:

Common Name	Stem Borer
Scientific Name	Chilo partellus
Attacking stage of pest	Larvae feeds on the maize's vascular system
Affected parts of the plant	Stem

Damage Causing stage of Stem Borer in Maize:

The most damaging stage of the stem borer in maize is undoubtedly the larval stage, when these hungry caterpillars wreak havoc on the plant's internal tissues.

Internal Destruction: Larvae tunnel within the stem, gnawing on vital vascular systems. This disrupts the flow of nutrients and water throughout the plant, hindering its ability to thrive.

Weakened Stalk: Tunneling weakens the stem's integrity, making it susceptible to snapping or lodging (falling over).

Favorable factors for stem borer in Maize:

• Warm temperatures: Stem borers are most active and breed rapidly in warm weather, with optimal temperatures for their development and reproduction ranging from 25°C to 30°C.
• High humidity: Similar to rust disease, humid environments, including periods of dew or extended overcast weather, favor egg hatching and larval survival.

Initial Symptoms of damage :

• Dead heart (central shoot withering): Primarily caused by Chilo partellus larvae feeding on the growing point, young leaves lose their green color and wilt, appearing like a withered bunch in the center of the plant.
• Small bore holes and frass: Look for tiny holes, often accompanied by sawdust-like frass around them, indicating larval entry points into the stem. These might be harder to spot initially.
• Stunted growth and wilting: Compared to healthy plants, infested maize may show slower growth and wilting due to disrupted nutrient and water flow within the stem.
• Slight leaf yellowing around bore holes: The area surrounding the entry point might exhibit subtle yellowing due to localized damage and tissue disruption.

Severe Symptoms of damage:

• Large bore holes and extensive tunneling: As larvae grow and tunnel deeper, the entry points become larger and frass accumulation increases. Visible tunnels may even run along the stem.
• Severe wilting and drooping: The plant wilts significantly due to extensive internal damage, eventually leading to drooping or lodging (falling over) if the stalk weakens.
• Presence of pupae or moths: In advanced infestations, you might see brownish pupae within the stem or even adult moths emerging from them, indicating a well-established population.

Control measures for Stem Borer in Maize:

Cultural Method of control for Maize stem borer

• Inter-crop maize with cowpea in 2:1 ratio.
• Release egg parasitoid, Trichogramma chilonis @ 2,50,000 /ha thrice at weekly intervals.

Chemical control measures for Maize Stem Borer

When infestation crosses 10% mark, spray the following insecticides:-

Products	Technical names	Dosage
FINISH -IT	All In One Larvicide	100 ml of this product per acre
Beauveria Bassiana		750 ml - 1 liter/acre
ema-5	emamectin benzoate 5 sg	76-88 gm/acre

FAQs related to Maize stem borer

Q. What are stem borers of Maize?

A. Maize stem borer is a harmful pest that poses a serious threat to maize crops. It is recognized by its yellowish-brown larvae with brown heads, which eventually develop into straw-colored moths.

Q. Which insecticide is best for stem borer?

A. Emamectin benzoate 5 sg (EMA 5) is one of the best insecticide recommended for the management of stem borer in Maize.

Q.What is another name of Stem Borer?

A. Yellow stem borer is another name for stem borer.

Q. What are the symptoms of stem borer infestation in Maize ?

A. Following are the symptoms of Maize stem borer

• Central shoot dries leading to dead heart
• Young larva feeds tender folded leaves causing "shot hole" symptom.
• Old larvae bores stem and feeds on internal tissues.
• Bore holes and tunneling noticed on stem.