NAFIS

Pests

Amaranth is susceptible to damage by foliar insects such as leafminers, leafrollers, cutworms, aphids, flea beetles, and mites.

Weevils

The most common is the pigweed weevil(Hypolixus haerens). Adult weevils feed on leaves, but the larval stage is more damaging because they bore into roots and stems.

Symptoms

• The adult weevil lays its eggs in branch crotches, and the larvae bore through stems to the root collar, causing hollowing of stems making them more susceptible to wind breakage.
• Plants wither and lodge.
• Rotting of bored stems and roots predisposing the plant to diseases.
• Extensive tissue discoloration, decay and cankers in branches, stems, and root collars

Weevil larvae feeding in amaranth stem

Adult weevil in amaranth stem

Amaranth plant with stem canker due to weevil attack

Canker and hollowed amaranth stem due to feeding by weevil larvae

Control

• Uproot and destroy attacked plants to reduce number of weevils

Stink Bugs
Bugs can cause severe damage to flowering head and seeds especial during the critical seed fill stage.

Bugs feeding on amaranth flowering head

Control

• Spray with permethrin, cypermethrin

Diseases

Damping-off

The disease is favoured by high soil water content and low soil temperatures. Also dense planting without sufficient aeration enhances disease development.

Causal agent - Pythium aphanidermatum, Rhizoctonia solani and Aphanomyces sp.

Symptoms

• Seeds may rot in the soil before emergence (pre-emergence damping-off)
• Seedlings may exhibit stem canker above the soil line and/or root necrosis.
• Affected seedlings eventually wilt (post-emergence damping-off).

Control

• Use disease-free seeds
• Avoid over watering
• Avoid dense planting

Choanephora blight

Infection is predisposed by injuries
The disease is spread by air currents and infected seeds. Warm, moist conditions favour disease development.

Causal agent - Choanephora cucurbitarium(a fungus).

Symptoms

• Wet rot of stems and leaves.
• Affected plant parts have hairy appearance (silk-like threads) consisting of fungal spores.
• Heavy defoliation during rainy season.

Control

• Use resistant varieties where available
• Plant certified disease-free seeds
• Avoid dense planting to allow sufficient aeration
• Practice good field sanitation