Sorghum (Sorghum vulgare)
1. Sorghum shoot fly Atherigona soccata Rond. (Muscidae: Diptera)
Distribution: Occurs throughout the country.
Nature of damage: The maggots bore into the shoot of young plants, a week after germination to about one month and as a result the central shoot dries up resulting in ‘dead hearts’. If it is a little later the mother plant may produce side tillers. But the tillers also may be attacked. The infestation often goes as high as 60%.
Life history: The adult is a small dark fly. It deposits whitish eggs singly on the central surface of the leaves. The eggs hatch in 1 – 3 days and the maggots which are yellow in colour migrate to the dorsal surface of the leaf, enter the space between the leaf sheath and the axis and make a clean cut at the base of the leaf. The growing point of the plant dies and decays on which the maggots feed. The larval period lasts for 6 – 10 days. Pupation takes place inside the stem itself and the adults emerge in about a week. Each female fly is capable of laying 30 eggs during its life time. Life cycle occupies 17 – 20 days.
Alternate hosts: The fly infests wheat, maize, small millets and grasses, besides sorghum.
(i) *A higher seed rate is adopted and the affected seedlings are pulled out and destroyed.
(ii) Application of 10% phorate (Thimet) or carbofuran 3% granules at the time of sowing at the rate of 2.5 kg a.i./ha.
(iii) Spraying of endosulfan @ 0.07% or cypermethrin @ 0.005% or cartap hydrochloride 0.5 kg a.i. /ha or triazophos @ 0.5 kg a.i. /ha twice a week after sowing or during second week.
* Seed rate of @ 12 kg/ha may be followed and the infected plants are removed.
2. Sorghum stem borer Chilo partellus (Swinhoe) (Crambidae: Lepidoptera)
Distribution: It is found in all places of India where sorghum is grown. It is also found to attack finger-millet, maize, pearl-millet, sugarcane and wild grasses.
Nature of damage: Presence of ‘dead heart’ in the early stages is the main symptom. The bore holes may be visible in contrast to the dead-heart caused by the stem fly. Later it acts as an internode borer and is found till the time of harvest. Yield is affected much and the quality of the fodder is also reduced. The damage caused to the crop by this pest is estimated to range between 70 – 80 %.
Life history: The moth is medium sized and straw coloured. The female lays flat oval eggs, about 200 on the underside of the leaves, near the midrib. The eggs hatch in 2 – 6 days. The larva is pale white with black dots and brown head. It bores into the stem near the node and feeds upwards. The larvae remain dormant in winter and hibernate. The average number of caterpillars per plant is four. The larval period lasts from 28 – 50 days in summer to 193 days in winter. Pupation take place inside the stem and the adults emerge in 7 – 15 days depending upon the climatic conditions. Total life cycle is completed in 30 – 40 days.
(i) Collection and destruction of the stubbles which are left in the field or heaped in one corner of the field since they act as a source of infestation, as the larvae hibernate in them.
(ii) Spraying of carbaryl 0.1 % or endosulfan 0.07% thrice at an interval of 15 days from a month after sowing.
(iii) Two whorl applications of 4 % endosulfan or 10 % carbaryl or 4% cartap hydrochloride granules, first at 5 kg /ha at 25 – 30 days after crop emergence and second at 10 kg/ha 10 – 15 days later. If infestation is severe, three applications at 5.0, 7.5 and 10.0 kg/ha are recommended.
3.Sorghum midge Contarinia sorghicola (Coq.) (Cecidomyiidae: Diptera)
Distribution: It has a world wide distribution and is considered to be one of the important pests of sorghum.
Nature of damage: The maggots feed on the developing grains and cause the developing grains to shrivel and severe infestation has a significant effect on the overall production of grains. The loss varies from 20 – 50 %.
Life history: The adult fly is very small, fragile and has a bright orange abdomen and a pair of transparent wings. The maggot feeds inside the developing grain and pupates there itself. It emerges between the tip of the glumes leaving the white pupal case attached to the tip in a characteristic manner. The life-cycle from egg to adult varies from 14 – 90 days.
(i) Spraying of endosulfan 35 EC* 1 litre, or phosalone 35 EC 1 litre, or Malathion 50 EC 1 litre, or carbaryl 50WP 2 kg per hectare at nearly 90% ear-head emergence and repeated after 4 or 5 days.
(ii) Phosalone 4% or endosulfan 4% or Malathion 5% or carbaryl 10% or quinalphos 1.5% dust at 12 kg/ha is also effective.
* EC = Emulsifiable Concentrate