Sorghum

Insect Management

Introduction

  • More than 150 species of insects have been reported to cause damage in sorghum. Among these shoot fly, stemborer, midge, headbug and panicle feeding caterpillars are the major pests.
  • The sucking pests viz., aphids and shoot bug are sporadic pests and occasionally cause economic damage. They are of minor importance.
  • The insect pests are major limiting factor in sorghum cultivation. The shoot fly is the key pest in India which cause heavy yield loss.

Crop Loss

  • Nearly 32% of sorghum crop is lost due to insect pest infestation in India. Panicle feeding pests cause an yield loss of 4 to 84%. In monitory terms, the losses due to insects have been estimated to be over US$ 1000 million annually in semi-arid tropics.

Stage of the crop
 Insect / Non insect pests
Common Name Scientific Name
Seedling stage (10-30 days) Shoot fly Atherigona soccata
Seedling -Maturity (25 -100 days) Stem borer Chilo partellus
Vegetative and flowering stage (30-80 days) Aphid Mite Rhopalosiphum maidis Melanaphis sacchari Oligonychus indicus
Vegetative stage (30-60 days) Shoot bug Peregrinus maidis
Flowering stage (60-80 days) Midge Stenodiplosis sorghicola
Flowering to grain maturity (60-90 days) Headbug Gram caterpillar Semi- looper Webworm Hairy caterpillar Calocoris angustatus Helicoverpa armigera Eublemma silicula Cryptoblabes gnidiella Euproctis subnotata

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Shoot fly (Atherigona soccata)

Damage symptoms

  • It is a seedling pest and damage occurs 1-4 weeks after the germination of the crop. The larvae (maggots) after hatching enters the leaf whorl and cut the growing point resulting in wilting and drying of central shoot known as "deadheart". When pulled, deadheart comes out easily and produce bad smell.
  • Damaged plants produce side tillers that may also be attacked.

Biology

  • Adult is a small grey coloured fly which lays cigar shaped white coloured eggs singly on the lower surface of the leaf.
  • The eggs hatch in 1-2 days and the larva (maggot) moves to the growing point between the folds of leaf. It cuts the growing point and feed on decaying tissue.
  • Pupation takes place in about 8-10 days in the base of the plant or soil. The pupal period lasts for 8 days.

Economic Threshold Level (Etl)

  • One egg per plant in 10% of the plant population in first two weeks of sowing or 10% deadhearts.

Management Practices

  • Take up early sowing immediately after the receipt of South West (June-July) or North East (September-October) monsoon to minimise the shoot fly incidence.
  • Pellet sorghum seeds with chlorpyriphos 20 EC or phosalone 35 EC or monocrotophos 36 WSC @ 4 ml/kg of seed. Mix 4 ml of insecticide in 20 ml of water containing 0.5 gm of gum. To this add 1.0 kg of seeds, pellet and shade dry.
  • Use increased seed rate upto 12.5 kg/ha and remove shoot fly damaged seedlings at the time of thinning.
  • Setup the TNAU low cost fishmeal trap @ 12 Nos/ha till the crop is 30 days old to attract and kill adult flies. Use moistened fishmeal @ 50 gm/trap. Change the fishmeal once in 10 days.
  • Apply any one of the following insecticides @ 500 ml/ha when the incidence exceeds ETL. Use 250 litre of spray fluid /ha.
  • Endosulfan 35 EC
  • Methyl demeton 25 EC
  • Dimethoate 30 EC

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Shoot bug (Peregrinus maidis)

Damage symptoms

  • Being a sporadic pest, under favourable condition, it produces several generations and cause heavy damage.
  • Nymphs and adults suck the sap from the leaf whorl and between leaf sheath and stem resulting reduced plant vigour and yellowing. In severe infestation the younger leaves start drying first. which extends gradually to lower leaves. Infestation at later stages of plant growth may twist the top leaves and inhibit panicle emergence. They also secrete honey dew which favour sooty mold development.
  • Adults are either brachypterous or macropterous. Female are yellowish brown and males are dark brown.

Management Practices

  • Apply entosulfan 4G or carbaryl 3G @ 8kg/ha in the whorls.

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Sorghum midge (Stenodiplosis sorghicola)

Damage symptoms

  • The larvae (maggots) feed on developing ovary resulting in chaffy florets. Under severe infestation panicles have blasted appearance. Pupal cases can be seen attached to the glumes of damaged spikelet.
  • A minute exit hole of midge parasitoid may also be seen on the upper glume.

Biology

  • Tiny, fragile and orange coloured female lays 75-100 eggs in the florets at anthesis. Eggs hatch in 2-3 days and the orange red coloured larvae feed on the developing grains inside the glumes.
  • Larval period is completed in 9-12 days and pupation takes place inside the glume. The pupal period lasts for 3-8 days.

Economic Threshold Level (Etl)

  • Five midges/ earhead.

Management Practices

  • Avoid staggered sowing in an area which favours multiplication of midge.
  • Setup light trap till midnight to attract and kill adults.
  • Apply any one of the following insecticides (dust) @ 25 kg/ha 3 and 18 days after panicles emergence.
  • Carbaryl 10 D
  • Phosalone 4 D
  • Malathion 5D

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Spotted stemborer (Chilo partellus)

Damage symptoms

 

  • The infestation starts 20 days after seedling emergence and continued till maturity.
  • The larvae after hatching feed on the surface of leaf and leaf whorls causing shot holes or windows. As severity of leaf damage increases, blend of feeding punctures and scratches on the leaf appears.
  • Larvae also bore into midrib. Older larvae migrate to the base of plant and bore in the stem where they feed on growing point leading to deadheart formation.
  • After the internode elongation and growing point moved upwards, larvae tunnel into the stem. Later infestation also occur in peduncle. Both stem and peduncle damage some times leads to production of complete or partial chaffy panicle. Infested peduncles may also break.

Biology

  • The straw coloured moth lays 400-500 flattened, over lapping, yellowish eggs in mass of 10-80 near the midrib on the under surface of leaves.
  • Eggs hatch in 4-5 days. Larval period is completed in 19 to 27 days. Larvae pupate inside the stem and adults emerge in 7-10 days.
  • During off-season, the larvae undergo diapause in stubbles and stalk. Diapause is broken after the on set of monsoon and larvae pupate.

Economic Threshold Level (Etl)

  • 10 % deadheart

Management Practices

  • Plough soon after harvest, remove and destroy stubbles to kill diapausing larvae.
  • Intercrop sorghum with lablab or cowpea @ 4:1 ratio to minimize infestation.
  • Setup light traps till midnight to monitor, attract and kill adult moths.
  • Apply insecticide when infestation crosses ETL.
  • Mix any one of the following insecticides with sand to make up a total quantity of 50 kg/ha and apply in leaf whorls
  • Quinalphos 5 G 15 kg
  • Phorate 10 G 8 kg
  • Carbofuran 3 G 17 kg
  • Carbaryl 4 G 20 kg
  • Endosulfan 4 D 10 kg
  • Phosalone 4 D 10 kg
  • Or spray endosulfan 35 EC 700 ml/ha or carbaryl 50WP 1.00 kg/ha. Use 500 litres of spray fluid /ha.

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Aphids (Rhopalosiphum maidis and Melanaphis sacchari)

Damage symptoms


Corn leaf aphid
Aphid damage
Sugarcane aphid

  • R. maidis is bluish green in colour with dark green legs. Lives inside the leaf whorl and suck the sap. It also feeds on the panicles and produce honey dew on which sooty mold grows. However, its infestation rarely reach damaging proportion. The infestation may result in the yellowing, tanning and drying up of leaves.
  • Yellow coloured. M. sacchari colonize on the under surface of the leaves and suck the plant sap. If damage is heavy the leaves dry up. Aphids also secrete honey dew on which sooty mold grow. They do not cause significant damage and yield loss.

Management Practices

  • Spray methyldemeton @ 1 litre/ha.

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Earhead caterpillars

Damage symptoms


Heliothis
Red hairy caterpillar

  • More than one species of caterpillars occasionally infest the earhead and cause economic damage. The panicle feeding caterpillars are
  • Gram caterpillar - Helicoverpa armigera
  • Semilooper - Eublemma silicula
  • Webworm - Cryptoblabes gnidiella
  • Hairy caterpillar - Euproctis subnotata

Biology

  • They feed on developing grains and destroy the grains mostly inside the panicles. Some species produce webs of silken threads inside the panicle or make small holes in the grains.
  • Compact panicles are prone to heavy damage. Affected panicles will be filled with frass.

Economic Threshold Level (Etl)

  • Two caterpillars /head

Management Practices

  • Setup light trap till midnight to monitor, attract and kill the adult moths.
  • Setup sex pheromone traps @ 12 /ha to attract male moths of H. armigera from flowering to grain hardening.
  • Apply two rounds of nuclear polyhedrosis viruses at 10 days interval @ 250 LE/ha along with crude sugar 2.5 kg + cotton seed kernel powder 250 g on the earheads to control H. armigera.
  • Apply any one of the following dusts @ 25 kg/ha
  • Carbaryl 10 D
  • Malathion 5 D
  • Phosalone 4 D

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Head bug (Calocoris angustatus)

Damage symptoms

  • Nymphs and adults such the sap from the developing grains. Damaged grains have distinct reddish brown feeding punctures and become shrivelled.
  • The infestation results in loss of grain quality and damaged grains becomes unfit for human consumption. Under severe infestation panicle becomes chaffy.
  • Damage also reduces the germination and predisposes the grains to mold attack.

Biology

  • Yellowish green coloured females lay about 150-200 eggs inside the spikelet from panicle emergence to post-anthesis.
  • The eggs hatch in 5-7 days. Nymphal period is completed in 15-17 days.

Economic Threshold Level (Etl)

  • 10 bugs/head.

Management Practices

  • Avoid staggered sowing in an area which favours multiplication of midge.
  • Setup light trap till midnight to attract and kill adults.
  • Apply any one of the following insecticides (dust) @ 25 kg/ha 3 and 18 days after panicles emergence.
  • Carbaryl 10 D
  • Phosalone 4 D
  • Malathion 5D

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Mite

Damage symptoms

  • They suck the plant sap from under surface of the leaves. The infested areas become pale yellow but later turn to reddish or brownish tan.
  • Depending on the severity of infestation the entire leaf change into reddish tan.
  • The plant growth and grain development is affected. Webbing can be seen on the under surface of the leaf.

Economic Threshold Level (Etl)

  • 5 mites/ cm2 of leaf area.

Management Practices

  • Spray 3.75 kg of wettable sulphur or 1500 ml dicofol per hectare. Spray fluid should be directed towards the under surface of the leaves.

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Tamilnadu

Sorghum

Sorghum Management