Insects pests of maize

INSECT PESTS OF MAIZE

R. Regmi Assistant Professor

Department of entomology

Major insect pests

• Maize stem borer, Chilo partellus (Lepidoptera: Pyralidae)

• White Grub, Phyllophaga rugosa/Holotrichia spp./Anomala dimidiate (Coleoptera: Scarabaeidae)

• Rice Ear- cutting caterpillar, Mythimna separata (Lepidoptera: Noctuidae)

• Flower Beetle, Chiloloba acuta (Coleoptera: Cetonidae)

• Wireworms, Agriotes spp (Coleoptera: Elateridae)

1. Maize stem borer 2, 3. White grub

4,5. Rice ear cutting caterpillar, Armyworm 6. Pollen beetle

Minor insect pests

• Rice Grasshoper, Hieroglyphus banian (Orthoptera: Acrididae)

• Grey Weevil, Myllocerus undecimpustulatus (Coleoptera: Curculionidae)

• Maize Cob worm, Helicoverpa armigera (Lepidoptera: Noctuidae)

• Cutworm, Agrotis segetum / A. ipsilon (Lepidoptera: Noctuidae)

• Leaf folder, Marasmia trapezalis (Lepidoptera: Pyralidae)

• Flea beetle, Monolepta signata (Coleoptera: Chrysomelidae)

• Maize shoot fly, Atherigonna spp. (Diptera: Muscidae)

• Banded blister beetle, Mylabris phalerata (Coleoptera: Meloidae)

Continue minor insects

• Pink borer, Sesamia inferens(Lepidoptera: Nocutidae)• Green Horned caterpillar, Melanitis leda

ismene(Lepidoptera: Satyridae)• Maize aphid, Rhopalosiphum maidis (Homoptera:

Aphididae)• Field cricket, Brchytrupes portentosus (Orthoptera:

Gryllidae)• Seed Bed Beetle, Heteronychus lioderes (Coleoptera:

Dynastidae)

Rice Grasshopper Helicoverpa

Cutworm Maize shoot fly

Maize aphid Armyworm

Banded blister beetle

Maize stem borer, Chilo partellus (Lepidoptera: Pyralidae)

• Most destructive pests of maize and sorghum.

• Its caterpillar damage maize and sorghum by boring into the stems, cobs or ear.

• The grown up caterpillar are about 20-25 mm long and dirty greyish white with black head and four brownish longitudinal stripes on the back.

• The adult are yellowish grey moths, about 25mm across the wing when spread.

Life cycle: • The insect breeds actively from March- April to October.

• The rest of the year it remains in hibernation as full grown larva in maize stubble, stalks or unshelled cobs.

• The larva pupate sometime in March and emerge as moths in the end of that moth or in early April.

• They are active at night, when they mate and lay eggs on the underside of the leaves of various hosts plants, particularly the early crop of maize.

• The eggs are flat oval, yellowish and are laid in overlapping clusters each containing up to 20 eggs.

• A female lays over 300 eggs during its life span of 2-12 days and the egg hatch in 4-5 days in summer.

Continue life cycle

• The young larva first feed on the leaves making a few shot holes and then bore their way downward through the central whorl as it opens.

• More shot holes becomes visible, indicating an earlier attack and the plant also shows dead heart.

• The larva becomes full fed in 14-28 days, passing through six stages and after making a hole in the stem pupate inside it.

• The life cycle is completed in about 4-7 weeks and there are probably 5 generation in a year.

• The full grown caterpillar of the last generation hibernates in stubble, stalks etc. and remain there till next spring.

Damage

• The damage is done by the caterpillars by eating inside of the stem.

• Production of dead hearts, weakening of the plants are the symptoms of attack of any stem borer.

Management• Destroying the stubble, weed and other alternate hosts of the stem

borer by ploughing field after harvest.

• Removal and destruction of dead hearts and destruction of infested plants showing early pin hole damage.

• Destruction of crop residues and chopping and stem harbouring diapauses larva could be effective.

• Clipping of lower leaves of maize (upto 4th )

• Release Trichogramma chilonis @one lakh per ha on 10-15 days old maize field crop.

• Spray crop 2-3 weeks after sowing as soon as borer injury to the leaves is noticed with either of Fenvalerate 20EC @100ml/ha, Cypermethrin 10EC@100ml/ha or deltamethrin 2.8EC@200ml using 150 liters of water.

• Use granular pesticide Furadan 3%G@12-15kg/ha

White grub, Phyllophaga rugosa (Coleoptera: Scarabaeidae)

White grubs are the larva of scarb “chafer” beetles.

They are creamy white in color, C- shaped with brown head with 3 pair of thoracic legs.

Some species of white grubs (Phyllogphaga spp.) feed on roots of maize plants.

Root damage is manifested by wilting seedling, poor plant stands, patches of tilted or lodged plants showing uneven growth.

Injured plants can easily be pulled out from ground.

The third instar is often the most damaging one and may be present in the soil for longest time.

The extent of damage and species composition varies from place to place.

The larva is the major damaging stage but adults also damage the leaf during night time.

Life Cycle Generally, most beetles takes 3 years to complete their life cycles in

temperate regions but only 2 years in optimum soil temperature.

Female white grubs lay the eggs in soil in pasture land or in fresh dung.

Hatching of egg takes place after 2-3 weeks.

First instar larva begin to feed on organic matter after hatching, later feed on plants roots.

With cooling soil temperature, larva descends into the soil profile, where they spend the winter.

In the spring, larvae begin their upward migration as soil temperatures increases.

The larval period ranges from 9-21 months and pupal period is 3-6 months.

Management• Different cultural practices such as ploughing, harrowing, hoeing, flooding

and fallowing of field.

• The use of well decomposed Farm yard manure (FYM).

• Light traps can be used for collecting adults beetles during night.

• Use of Metarrhizium and Beauveria based biopesticide (1- 1 kg of Metarrhizium & beauveria mixed with 25 kg of FYM and kept for 8 days in shade. Using this during land preparation).

• In Highly affected area, use Chloropyriophos 10 G @ 1kg per Ropani before sowing.

• Treat the seed before sowing with 12.5ml of Chorpyriphos 20EC per Kg of seed.

• Kills the beetles by spraying 500g of carbaryl 50WP in 250 liter of water per ha on preferred host like Zizyphus, Guava, Grapevine etc.

• Apply 30Kg of carbofuran 3G per ha in the soil at or before sowing.

Armyworm, Mythimna separate (Lepidoptera: Noctuidae)

• The armyworm is a pest of graminaceous crops all over the world mainly pests of maize, wheat, sugarcan, jowar, bajara.

• The larva feed voraciously and migrate from one field to another.

Life cycle: • The adult moths of armyworm are pale brown.

• They live for 1-9 days and lay eggs singly in row or in clusters on dry or fresh plants or on the soil.

• The eggs are round, light green when freshly laid and turns pale yellow and finally black.

• The egg hatch in 4-11 days from March to May and in 19 days in December- January.

• Freshly emerged larva are very active, dull white and later turn green.

• In the spring, the larval stage is completed in 13-14 days, but in winter it is prolonged to 88-100 days.

• In the pre-pupal stage, the insect spins a Cocoon.

Continue life cycle• The pre-pupal stage last 1-11 days during January to May.

• Pupation usually takes place in the soil at a depth of 0.5- 5 cm, but it may also occur under dry leaves among the stubble or fresh tillers.

• Generally, the larva before pupation seem to select sites near the water channels.

• The pupal stage is completed in 9-13 days in May and 36-48 days in the winter months.

• The survival of the pupae depends on soil moisture.

• The population build up starts in the beginning of March & increase with the rise of temperature in the spring.

Damage• In the early stages, they feed on tender leaves in the central

whorl of the plant.

• As they grow, they are able to feed on older leaves also and skeletonize them totally.

• The grown up caterpillar throw out faecal pellets, which are quite prominent.

• In case of a severe attacks by the armyworm, whole leaves including the mid rib, are consumend and field look as if grazed by cattle.

• The larva of all instars feed mainly on leaves.

• Fourth and older instars larvae cause the main harm, roughly gnaw out and eating around the leaf blade and damaging inflorescences, ears, growth points and grain in ears .

Management: • Collecting and destroying the caterpillar.

• Spray 500ml of dichlorovous 85 SL or 3 Kg of carbaryl 50WP or 1 Lit of Quinalphos 25EC in 250 Liters of water per ha.

Flower beetle, Chiloloba acuta (Coleoptera: Cetonidae)

• They are pollen feeders and are common on flowers and may occur under loose bark in debris.

• Flower beetle caused damage in rice, maize, sorghum, millets etc.

• They also feed on the leaves, bud and flower.

• The main injury consists in feeding and destroying blossom petals.

• If many beetles are present, their excrement often discolor the blossom.

• The adult beetles are shiny metallic green and appear sometimes red or deep blue.

• The are irregularly covered with hairs on the upper side but more densely on the sides and underside.

Life cycle: • Female lays hundreds of tiny, oval eggs, usually on a leaf

or in rotten wood, which usually takes 4-10 days to hatch.

• The larva pass through 3-5 instars, they vary in shape and size depending on where they live and what they feed on.

• They generally appears grub like with a well defined head capsule, which may be highly sclerotised.

• The larvae of Chiloloba species feeds on trunks, branches or twigs of dying plants.

• The pupal stage is usually found during the winter period and adult emergence occurs in spring.

Management

• Hand collection of adults beetle

• Collection with help of sweep nets

• Spray 500ml of dichlorovous 85 SL 1 Lit of Quinalphos 25EC in 250 Liters of water per ha.

Wireworms, Agriotes spp (Coleoptera: Elateridae)• Wireworm is the common name of the larva of click beetle.• The name ” click beetle” originates from the habit of clicking its body into

the air. • The adult beetle are harmless feeding on pollen, however, the larva

belongs to the most destructive soil insect pests. • They are important pests of potatoes and other crops including cereals &

also damage germinating seeds. • Most adult are light to dark brown and dull, between 6 to 10 mm long and

about 2 mm wide. • The body of the beetles is convex.• The egg are white, nearly globe shaped about 0.5 mm in diameter. • The larva are dark yellow up to 25mm long and 2 mm wide. The apex of the

last segment of the larval body is sharp pointed. • The larva are hard, nearly cylindrical and shining as those in all the species. • Pupae are white 9-12 mm long.

Life cycle• The females lay eggs in cluster or singly on roots or into

soil at a depth of 3-15 cm.

• The total female fecundity amounts to 50-350 eggs.

• The larva develops during 3-5 years, molting 8-11times.

• Overwintering takes place at a soil depth of 20-50cm.

• The larvae prefer moist soils, As soils dry out, they migrate in deeper soil layer.

• Larger larvae are able to starve several months.

• A generation lasts 3-6 years depending on food availability and environmental conditions.

Continue Life cycle

• Plants in unploughed soil and grassland represents the primary food source for wireworm.

• Therefore, problems arise when infested pastures are ploughed and planted with crops.

• Because of their extended life cycle, wireworm damage may persists for 2-3 years after.

• The most significant damage is caused to germinating seeds and seedling during cold, wet springs.

• Wireworm injury is often associated with a small feeding hole at the base of the plant, which may kill the growing point and stunt plant growth.

Damage• The wireworm feed on seeds, seedling and

underground parts of crops & weed.

• The wireworm are more harmful for the grain cereals, especially for maize, sunflower, potato, Solanaceous and Cruciferous vegetables, carrot, beet, turnip etc.

• Wireworm cause shoot thining, stunting of damaged plants and quality loss of tuber crops like potato.

Management• Crop rotation that include alfa-alfa and high

glucosinolate Brassica spp may help in management of wireworm.

• Field drying and summer ploughing

• Flooding field with water at least for 2 weeks

• Use of wheat as trap crop while growing maize and other cash crops

• Use of Metarrhizium and Beauveria based biopesticide (1- 1 kg of Metarrhizium & beauveria mixed with 25 kg of FYM and kept for 8 days in shade. Using this during land preparation).

Thank you