Brinjal (Solanum melongena)
1. Shoot and fruit borer (Leucinodes orbonalis Guen.) (Pyraustidae: Lepidoptera)
Distribution: This is the most serious pest of brinjal throughout the country. Its other host plants include potato, Solanum xanthocarpum, S. indicum, S. nigrum etc.
Nature of damage: The larva bores into tender shoots in the early stage and causes “dead hearts”. It also bores into flower buds and developing fruits causing shedding of buds and making the fruits unfit for consumption and marketing. The infestation may go as high as 70 per cent on brinjal.
Life history: The moth has brownish and red markings on the whitish fore wings. The female lays about 250 eggs singly on tender shoots and developing fruits of brinjal. The pinkish larva with sparsely distributed hairs on warts on the body and a brownish head measures 16 – 20 mm long. It pupates in a tough grayish cocoon on the plant itself. The egg, larval and pupal periods occupy respectively 3 – 5, 15 and 6 – 8 days.
Management strategies :
(i) The damaged portions of the plants and fruits should be removed and destroyed.
(ii) Need based spray application of phosalone 0.07 % or carbaryl 0.1% or profenofos 0.05 % or cypermethrin 0.025 % controls the pest.
2. Spotted leaf beetle (or Hadda Beetle) Henosepilachna vigintioctopunctata (Fabr.) (Coccinellidae: Coleoptera)
Distribution: It is found in different parts of South East Asia. The insect is considered to be one of the important pests of brinjal, sometimes becoming serious on it. It also breeds on brinjal, other solanaceous plants like Solanum tuberosum, S. nigrum, S. xanthocarpum. S. torvum, tomato, Datura sp., Physalis sp. and Withania somnifera.
Nature of damage: The grubs and adults scrape the leaves in a characteristic manner and feed. They feed on the epidermal layers of leaves which get skeletonized and gradually dry away. They affect the crop in all the stages.
Life history: The brownish hemispherical beetle has 12 – 28 black spots on the elytra. The female lays elongate, spindle-shaped yellowish eggs in groups of 10 – 20 on the under surface of leaves. About 120 – 180 eggs may be laid by a female. The egg period is 2 – 4 days. The yellowish spiny grubs become full grown in 10 -35 days and pupate on the leaf or stem. The pupa is hemispherical, yellowish with spines on the posterior part. The anterior portion being devoid of spines. Adults emerge in a week and live for a month feeding on leaves. The total life-history takes 17 – 50 days depending on weather conditions.
Management practices / strategy:
(i) In the initial stage, collection and destruction of affected leaves alongwith the eggs, grubs and adults.
(ii) Spray application of carbaryl 0.1% or cypermethrin 0.025% or profenofos 0.05%.
3. Grey weevil, (Myllocerus subfasciatus G. or M. maculosus) (Curculionidae: Coleoptera)
Distribution: It is a polyphagous pest occurring on a number of crops like cotton, sorghum, pearl millet and maize all over India.
Nature of damage: The adult beetles feed on leaves of brinjal and the grubs feed on roots and cause wilting and death of plants. Occasionally the insect assumes serious proportions on the crop.
Life history: The brownish weevil lays about 500 eggs in the soil about 80 – 100mm deep. The incubation period is 3 – 11 days. The grubs become full grown in 28 – 34 days and pupate in the soil-in earthen cocoons. The adults emerge in about 5 – 7 days. Total life cycle is completed in 6 – 8 weeks.
(i) Application of 5% carbaryl dust.
(ii) Drenching 0.1% chlorpyriphos emulsion into the soil before transplanting.
(iii) Inter-culture of the crop regularly to prevent population build up and carry over of these weevils.
4. Aphid Aphis (gossypii Glover and Myzus persicae) (Sulzer) (Aphididae: Homoptera)
Distribution: Both the species occur in all places in all seasons. The incidence is more in cool and humid seasons. Both are cosmopolitan in distribution and are absent only from colder parts of Asia and Canada. A. gossypii is also found attacking cotton, bhindi, chillies and guava.
Nature of damage: Both nymphs and adults are found in large number sucking the cell sap from leaves and tender apical shoots. The under surface of the leaves get crinkled and slightly curled backwards. The vitality of the plant is diminished and the plants turn yellow, get deformed and dry away. Besides this direct damage they also secrete copious quantity of honeydew on which sooty mould grows rapidly covering the affected parts with a thick black coating, which interferes with the photosynthetic activity of the plants. The infested plants become weak, pale and stunted in growth which consequently results in reduced fruit size.
Life History: Nymphs of A. gossypii are greenish-brown or yellowish in colour while adults are yellowish-green to dark green in colour, little over one mm in length and have a pair of siphunculi in the posterior side of abdomen. Wings when present are transparent with black veins. A. gossypii breeds during winter on a number of vegetables including brinjal from where it migrates in the month of April to melons and by June end return to cotton. Reproduction in case of A. gossypii is parthenogenetic viviparous and rate of multiplication is often phenomenal.
Adults of M. persicae are usually of green colour but may be pale brown to pinkish, 1.5 – 2.5 mm long with long clavate siphunculi. M. persicae reproduces by parthenogenetical viviparity during summer, monsoon and autumn seasons but sexually in cooler regions during winter. Adults normally perish due to severe cold and eggs overwinter in cracks and crevices on the bark of various temperate fruit trees. When the temperature rises, the eggs hatch and nymphs start feeding on blossoms.
They mature in 3 – 4 days and reproduce parthenogenetically producing young ones which develop into wingless adults. After 2 – 3 generations when the temperature rises further or when there is too much crowding of these aphids, the winged forms are produced and these migrate to other crops including brinjal; again with fall in temperature, they migrate back to temperate fruit trees.
(i) Two to three sprayings at 10 – 12 days interval with 0.05% dimethoate or monocrotophos or 0.01% imidacloprid.
(ii) Conservation of the coccinellids and syrphids that are found to feed on the aphids will reduce the numbers considerably without any insecticidal spray.
5. Leaf hopper (Amrasca biguttula biguttula) (= Empoasca devastans Dist.) (Cicadellidae: Homoptera)
Distribution: Distributed all over India; but particularly serious in Sind, Punjab and Tamil Nadu. It is a polyphagous pest attacking okra, brinjal, beans, castor, cucurbits, hollyhock, potato, sunflower and other malvaceous plants.
Nature of damage: The nymphs and adults remain on the under surface of the leaves and suck the cell sap and while feeding inject their toxic saliva. As a result the plant become stunted, the leaves crinkle, turn yellowish and become cup shaped. Brownish or reddish colour may develop along the edges of the leaves. This is called the ‘hopper burn’. This pest is very active from September to January.
Life history: The adult is a slender green insect. Elongate, yellowish eggs are laid singly inside the leaf vein on the under surface of the leaves. A female lays 15 – 30 eggs, leaves of 35 – 40 days old are preferred for egg laying. Egg hatch in 4 -10 days. Nymphs are green and wedge shaped. The first and second instar nymphs feed mostly near the base of the leaf vein. Then they distribute themselves throughout the leaf and feed from the under surface. The nymphs develop into adults in 7 – 21 days. They breed throughout the year.
(i) Spraying of 0.04 % phosphamidon or 0.05% monocrotophos or 0.01% imidacloprid.
(ii) Application of 5% dimethoate granules in seed furrows @ 20 kg/ha.