Introduction
- Pest is an organism that causes considerable damage to plant and draws the attention of man.
- Over 130 insect pests have been reported to infest maize but only very few are serious and require management. Amongst these, the most serious pests are the stem borers.
- The spotted stem borer, Chilo partellus is the key pest throughout India and the pink borer, Sesamia inferens is serious pest in Peninsular India.
- Shoot fly species Atherigona soccata and A. naqvii found to be serious in spring maize in Northern India.
- The losses ranging 26.7 to 80.4 percent have been reported due to C. partellus. Losses due to S. inferens found varied from 25.7 to 78.9 percent.
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Important Pests At Different Stages Of Maize
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Pest species
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Pest status
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Pest Stage
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Damage
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Spotted stem borer :Chilo partellus
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Major
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Larva
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Produces pin holes on leaves initially and
dead hearts later
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Pink borer : Sesamia inferens (Noctuidae,
Lepidoptera)
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Major
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Larva
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Produces pin holes on leaves initially and
dead hearts later
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Shoot fly Atherigona naqvii A.
soccata (Anthomyiidae, Diptera)
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Major
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Maggot
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Death of central shoot resulting in dead
heart
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Gram caterpillar Helicoverpa armigera
(Noctvidae, Lepidoptera)
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Occasional
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Larva
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Leaves and green cobs
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Red hairy caterpillar Amsecta moori
A.albistriga (Arctiidae,Lepidoptera)
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Occasional
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Larva
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Defoliation
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Corn aphid Rhopalosiphum maidis
(Aphididae,Homoptera)
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Minor
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Adults & nymphs
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Suck sap from all parts of the plant
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Corn Leaf Aphid : Rhopalosiphum maidis
Family : Aphididae
Order : Homoptera
Occurrence
- The aphid is widely distributed and appears in serious form occationally during drought years.
Nature of damage
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- Maize plants at the end of mid whorl stage are usually attacked.
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- Aphids suck sap from plants and cause yellowing and mottling. Diseased plants may become stunted and turn reddish as they mature.
- If young plants infected they seldom produce ears. The aphid colony may some time cover completely the emerging tassels and the surrounding leaves preventing the emergence.
- Ears and shoots are also infested and seed set may be affected. Honey dew excreted by aphids favours the development of sooty molds.
Control
- One spray of systemic insecticides like dimethioate or monocrotophos at 0.1% will controls the aphids.
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Pink Borer: Sesamia inferens
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Family : Noctuidae
Order : Lepidoptera |
Occurrence
- A serious pest in peninsular India more severe in rabi.
- Other hosts include Ragi, Sorghum, Bajra, Wheat, Paddy and Sugarcane.
- Moth is medium sized stoutly built having straw coloured forewings with a mid longitudinal dark brown broad triangular streak. Hind wings are white.
Life cycle
- Round pearl like yellowish eggs ranging 80-300 are layed in 2-3 longitudinal rows usually with in the sheaths of bottom leaves of young maize plant of two to three weeks old. As the time for hatching approaches, eggs become brown or shy grey.
- Full grown larvae are stout smooth about 25 to 30 mm in length purplish pink on the dorsal side and white on ventral side. Life cycle is completed in 6-7 weeks with 4-5 generations in a year.
Nature of damage
Oblong holes |
Larval feeding |
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- Newly hatched larvae remain in group behind the leaf sheath and begin chewing on the stem and epidermal layer of the sheath. Some migrate to neighbouring leaf sheaths, while others penetrate the stem.
- Whorl feeding of larvae results in rows of oblong holes in unfolding leaves unlike round shot holes produced by Chilo partellus.
Cob and Tassel at oneplace |
- Later they bore in to central shoot resulting in the drying up of the growing point and formation of dead heart in young maize plant as a result of larval feeding some times the bottom internodes show circular ring like cuts.
- Severe damage causes the stem to break. Severely infected plants due to stunting may appear to have some times the cob and tassel at one place.
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Management Of Stem Borers
- Pest management strategies viz., cultural, biological, host plant resistance, chemical and integrated pest management for maize stem borers can be practiced to effectively control both stem borers Chilo Partellus and Sesamia inferens.
Cultural Control
Farm sanitation
- Collection and burrying stubble and stalks or ploughing and destroying crop residue, removal of infested plant parts or infested plants at hoeing are recommended.
Inter cropping
- Growing maize in association with various legumes significantly reduced C. partellus damage in maize. Also intercropping maize with soyabean gave a considerable reduction in C. partellus and S. inferens and 9.2% increase in grain weight per plant.
- Therefore intercropping has a great potential in reducing the pest incidence.
Exploitation of ovipositional behavior
- The ovipositional behavior of C. partellus could be exploited for its management.
- Clipping of lower leaves of maize (up to fourth) on which most of eggs of C. partellus are laid, reduced damage to some extent.
- As this practice may not be practicable in a large scale, they recommended earthing-up of the crop to burry the lower leaves as a possibility for reducing initial infestation.
Plant Resistance
- Intensive screening to identify resistance sources against (C.partellus) yielded an important germplasm source. Antigua Gr. 1 and few breeding lines.
- Sources of tolerance to S. inferens have been identified. These materials are currently being used in Directorate of maize Research and also in other centres breeding programs.
- At this time, however, stem borer resistant cultivars / hybrids have yet to be released in the semi arid tropics.
- Further more, the work on the screening for resistance is being done extensively and continuously and there is every possibility of identifying sources of resistance to borers and development of resistant hybrids/varieties.
Biological Control
- Many natural enemies have been reported to attack C. partelllus.
- Among the parasitoids reported, Trichogramma spp. as egg parasitoids and Aphanteles favipes and T. Chilonis and larval parasitoids are important.
- T. cllilonis has been found parasitising egg masses of C. partelllus upto 70% . A. flavipes is the most dominant and most widely distributed larval parasitoid of C. partellus in India with a parasitisation ranging from 5.3 - 42.8%.
- Even though a number of natural enemies have been reported on maize borers, but in general, the efficiency of natural enemies in particular farming environments is not known.
- The scope for successfully controlling maize stem borers with natural enemies is limited by the short cropping period and the lack of continuous habitat for natural enemies.
Chemical Control
Seed treatment |
- Seed treatment with Carbofuran 35 ST having 1/3 a.i.
- Seed treatment with Carbofuran (40F) 5% W/W @ 2.5g/kg of seed was also found effective against S. inferens.
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Effective control schedule
- 1st Foli al 15 kg/ha a fortnight later against C. partellus.
- 2nd application of 4% granules al 15 kg/ha a fortnight later against C. partellus.
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Stem Borer: Chilo partellus
Occurrence
- It is the most destructive pest of maize and Sorghum in Srilanka, India, Pakistan, Afghanistan, Uganda, Central and East Africa.Pest is found throughout India.
Nature of damage
- The young larvae first feed on the leaves, making a few shot holes and then bore their way downwards through the central whorl as it opens.
- More shot holes become visible, indicating an earlier attack and the plant also shows dead-hearts. Caterpillars damage maize by boring into the stems, cobs or ears.
- Stem borer infestation results in pinhole damage in the leaves initially and "dead hearts" subsequently.
Life-cycle
- The insect breeds actively from March-April to October and for the rest of the year it remains in hibernation as a full-grown larva in maize and sorghum stubble, stalks or unshelled cobs.
- The larvae pupate sometime in March and emerge as moths in the end of that month or in early April.
- They are active at night, when they mate and lay eggs on the underside of the leaves of various host plants, particularly the early crops of maize and sorghum grown as fodder.
- The eggs are flat, oval, and 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 eggs hatch in 4-5 days in summer.
- The larva become full-fed in 14-28 days passing through six stages and after making a hole in the stem pupates inside it.
- The life cycle is completed in about 3 weeks and there are probably 5 generations in a year. The full-grown caterpillars of the last generation hibernate in stubble, stalks, etc, and remain there till the next spring.
Management Of Stem Borers
- Pest management strategies viz., cultural, biological, host plant resistance, chemical and integrated pest management for maize stem borers can be practiced to effectively control both stem borers Chilo Partellus and Sesamia inferens.
Cultural Control
Farm sanitation
- Collection and burrying stubble and stalks or ploughing and destroying crop residue, removal of infested plant parts or infested plants through hoeing are recommended.
Inter cropping
- Growing maize in association with various legumes significantly reduced C. partellus damage in maize.
- Also intercropping maize with soybean gave a considerable reduction in C. partellus and S. inferens and 9.2% increase in grain weight per plant.
- Therefore intercropping has a great potential in reducing the pest incidence.
Exploitation of ovipositional behavior
- The ovipositional behavior of C. partellus could be exploited for its management.
- Clipping of lower leaves of maize (up to fourth) on which most of eggs of C. partellus are laid, reduced damage to some extent.
- As this practice may not be practicable in a large scale, they recommended earthling-up of the crop to bury the lower leaves as a possibility for reducing initial infestation.
Plant Resistance
- Intensive screening to identify resistance sources against (C. partellus yielded an important germplasm source. Antigua Gr. 1 and few breeding lines.
- Sources of tolerance to S. inferens have been identified. These materials are currently being used in Directorate of maize Research and also in other centres breeding programs.
- At this time, however, stem borer resistant cultivars / hybrids have yet to be released in the semi arid tropics. Further more, the work on the screening for resistance is being done extensively and continuously and there is every possibility of identifying sources of resistance to borers and development of resistant hybrids/varieties.
Biological Control
- Many natural enemies have been reported to attack C. partelllus.
- Among the parasitoids reported, Trichogramma spp. as egg parasitoids and Aphanteles favipes and T. Chilonis and larval parasitoids are important.
- T. Cllilonis has been found parasitising egg masses of C. partelllus upto 70% . A. flavipes is the most dominant and most widely distributed larval parasitoid of C. partellus in India with a parasitisation ranging from 5.3 - 42.8%.
- Even though a number of natural enemies have been reported on maize borers, but in general, the efficiency of natural enemies in particular farming environments is not known.
- The scope for successfully controlling maize stem borers with natural enemies is limited by the short cropping period and the lack of continuous habitat for natural enemies.
Chemical Control
Seed treatment |
- Seed treatment with carbofuran 35 ST having 1/3 a.i.
- Seed treatment with carbofuran (40F) 5% W/W @ 2.5g/kg of seed was also found effective against S. inferens.
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Effective control schedule
- 1st Foliar application of Endosulfan 0.1% 15 days after sowing
- 2nd application of 4% granules @15 kg/ha a fortnight later against C. partellus.
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Shoot Fly: Atherigona soccata, A.naqui
Occurrence
- Very serious pests of maize in South India. In North India maize crop is not effected much except spring season in tarai area.
Nature of damage
- The attack is maximum when the crop is in seedling stage.
- The tiny maggots creep down under the leaf sheaths till they reach the base of the seedlings.
- After this they cut the growing point or central shoot which results in the formation of characteristic dead hearts.
Control measures
- Water logging condition should be avoided.
- Application of 10% Phorate granules in furrows before sowing @15kg/ha should be done and the insecticide should be covered with thin layer of soil after which seed should be sown.
- Spraying with 0.01% Metasystox after one week of germination.
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Shoot Bug : Peregrinus maidis
Family:Delphacidae
Order :Homoptera
Occurrence
- Occasionally serious pest on maize.
- Found attacking maize and sorghum in South India and Madhya Pradesh with peak activity during August-October.
- Adult is yellowish-brown to dark brown with translucent wings in macropterous forms while brachypterous forms have underdeveloped wings, nymphs are yellowish and soft bodied.
Nature of damage
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- Adults and nymphs suck sap, resulting in unhealthy, stunted and yellow plants.
- Leaves wither from top down words and plants die if attack is severe.
- Honey dew excreted by the insects causes growth of sooty mold on leaves.
- Mid ribs of leaves turn red due to egg laying and may dry subsequently.
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Control
- Predators of coccinellid predators, Coccinella septumpunctata and Menochilus sexmaculata if available will control the pest
- If Sufficient population of predators is not available spraying any systemic chemical like monocrotophos or dimethioate at 0.1% will control the disease.
- 15days after sowing spray 0.1% Endosulphan.
- After 15 days of this spraying, 15kg 4% endosulphan granules per hectare are to be applied.
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Integrated Pest Management And Its Difficulties
- The individual control measures may not be sufficient to adequately control maize stem borers and it is necessary to integrate the available methods.,
- In the integrated management of maize borers host plant resistance and cultural practices should be major components. The IPM recommendations are that they are too complicated to be adopted by farmers.
Difficulties encountered in IPM
- Recommendations for stem borer management although appear promising have not carried for beyond the research stations.
- Farm sanitation can either not be improved or only be improved at high cost.
- Sowing dates are confined by several constraints and likely to be well timed in traditional farming systems that have evolved over long periods.
- Rotations are often obstructed by the vagaries of weather.
- Stem borer control through consistent intercropping is to be standardized.
- Biological control is insufficient.
- Chemical control even though efficient but limited by economical constraint.
- Integrated stem borer management finally is likely to be severely constrained by the limited management capability of farmers.
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