Learn about the pests that damage vegetables and its control.
1. Potato Tuber Moth, Phthorimaea Operculella (Zeller) (Lepidoptera: Gelechiidae):
This pest occurs especially in hot and dry climates. It is destructive to potato and also attacks tobacco, tomato, brinjal and solanaceous weeds. It is particularly serious on potato in Himachal Pradesh. The larvae cause the damage and are recognized as pinkish-white or greenish caterpillars, with dark-brown heads.
They are about 20 mm in length. The adult is very small narrow-winged nocturnal moth, about 13 mm across the wings when spread. It is greyish brown with mottling of dark brown. Another species of tuber moth attacking potato is P. heliopa (Lower).
Life-Cycle:
If food is available and the climatic conditions are favourable, this pest may breed throughout the year. In cold weather, the life-cycle is much prolonged. Early in the spring, the moths escape from store-houses and start breeding in fields. A female, on an average, lays 150-200 eggs singly on the underside of leaves or on exposed tubers.
The larvae first produce blotch mines on leaves but subsequently, they work their way into the stems. The larval stage in summer lasts 2-3 weeks and the mature larva pupates in a greyish silken dirt-covered cocoon, which is about 13 mm in length. The moths emerge in 7-10 days. They complete their life-cycle in about one month and there are usually 5-6 generations in a year.
Damage:
In warm dry climates extensive damage may be done to the crop; but the potato tubers kept in cold stores escape damage. Later generations in the field infest the tubers also. At the time of digging, the moths may lay eggs on tubers. The larvae, on hatching, may work their way just under the skin and, later, may make tunnels through the flesh, causing damage to the tubers.
Control:
(i) All the infested tubers should be removed and destroyed.
(ii) Cold storage of tubers also helps in suppressing the pest.
(iii) The pest can be checked by spraying 2.5 kg of carbaryl 50 WP in 625 litres of water per ha or by dusting seed potato with 150 g of malathion 2 per cent per 100 kg. Repeat spraying 2-3 times at fortnightly intervals and do not dust the edible potatoes.
(iv) If potato tubers in the stores get infested, fumigation with carbon disulphide @ 2-3 litres per 100 m3 should be done.
2. Aphid, Aphis Gossypii Glover and Myzus Persicae (Sulzer) (Hemiptera: Aphididae):
The leaves curl, turn pale bronze and dry up as a result of jassid and aphid attack. The crop is stunted and has blighted appearance. M. persicae appears late in the season. Besides sucking the cell sap, it transmits viruses and lowers the quality of the seed crop.
Control:
(i) Spray the crop with 750 ml of dimethoate 30EC or oxydemeton methyl 25EC or 200-250 ml of phosphamidon 85SL in 250 litres of water/ha on the appearance of pest. Give another spray after 10 days,
(ii) In case of the crop meant for seed, apply 12.5 kg of phorate 10G to the soil at the time of first earthing up.
3. Cutworms, Agrotis Ipsilon (Hufnage) and Ocbropleura Flammatra (Denis & Schiffermuller) (Lepidoptera: Noctuidae):
The cutworms cause considerable damage from February to March by cutting the young plants at the ground level and later on by making holes into the tubers.
Control:
Drench the soil around the plant and the ridges with chlorpyriphos 20EC. @ 2.5 litres/ha in 1000 litres of water at the appearance of the pest in January to February.
4. Tomato Fruit Borer, Helicoverpa Armigera (Hubner) (Lepidoptera: Noctuidae):
Tomato fruit borer is one of the most destructive pests of tomato. The adults lay majority of the eggs on the upper and lower leaf surfaces of the first four leaves in the top canopy. The larvae scrape the tomato foliage until early or late second instar stage. Thereafter, the larva bores into the fruit making it unfit for marketing. In severe cases of infestation, more than 80 per cent fruits get damaged.
Control:
(i) Deep ploughing after harvesting the crop to expose the pupae for natural killing affords good protection.
(ii) Hand picking of larvae in small area is also recommended.
(iii) Use of African marigold (Tagitus erecta) as a trap crop is useful for control of fruit borer.
(iv) Give three sprays at 2 week intervals starting from the initiation of flowers with any of the following insecticides using 250 litres of water/ha: 2.0 litres of malathion 50EC, 2.0 kg of carbaryl 50WP, 250 ml of fenvalerate 20EC, 500 ml of cypermethrin 10EC, 400 ml of deltamethrin 2.8EC, 1.5 litres of profenophos 50EC, 75 ml of flubedamide 480 SL.
5. Golden Cyst Nematode, Globodera Rostochiensis Wollenweber (Tylenchida: Heteroderidae):
This nematode is wide-spread in Europe, the Americas, Algeria, Israel and Japan. It has recently been recorded in India in the Nilgiri Hills and near Simla. It is a notorious pest of the potato crop but is also found infesting tomato, brinjal, chillies and some solanaceous weeds. The infested plants, when pulled out, show clusters of white and golden spherical bodies attached to the roots and tubers, about the size of a sand grain.
These are the cysts of mature female bodies and generally appear when the potato crop is 2-3 months old. If these cysts are crushed and examined under a microscope, 200-600 eggs will be released. The other eelworms attacking potatoes include Meloidogyne incognita and M. javanica.
Life-Cycle:
When host plants are not available, the eggs remain dormant in the cyst. In the presence of the crop, the plant roots secrete some sort of exudate which is believed to stimulate the hatching of eggs within cysts. The young larvae remain within the cysts and moult once before they are set free.
They wriggle through the soil and reach the roots of the host plant and bore into them near the tips, the head being directed towards the conducting tissue. There, they feed and undergo three more moults. When full-fed, the males measure about 1 mm in length. At that stage, they leave the roots and move around in search of females.
The female larvae, which become enlarged and swollen after each moulting, remain sedentary with the neck and head embedded in root tissue and the main portion of the body protruding. The males approach the females for mating and after the latter have been fertilized, they swell up further becoming almost spherical. It is at this stage that the pest is visible to the unaided eye as white or golden specks attached to the roots.
At first, the colour is white but gradually turns golden and finally dark brown. The body wall then becomes thickened and forms a cyst. When the plants are harvested, these cysts get dislodged, drop into the soil and remain dormant till the next potato season. The life-cycle is completed in about 5-7 weeks. Only one generation is normally completed in a year.
Damage:
Larvae of the golden cyst nematode feed on the juice sucked from the roots. The attacked plants remain stunted and give a dull and unhealthy appearance. The lower leaves turn yellow, wither and drop off. With young leaves at the top remaining intact, the plants give a ‘tufted head’ appearance. The root system is poorly developed and the size of tubers is reduced considerably. Badly infested plants may give little or no harvest. The repeated cultivation of potatoes leads to a rapid buildup of the nematode population.
Control:
(i) The preventive measures useful in checking its spread include avoiding the cultivation of potato, brinjal, tomato and chillis in infested fields; adjusting the crop rotation so that potato and related crops in the same field are sown after 4 years and using uninfested potatoes as seed.
(ii) The nematode can be controlled by using 450 litres of DD mixture or 225 litres of EDB or 25 kg of Nemagon per ha.
6. Onion Thrips, Thrips Tabaci Lindeman (Thysanoptera: Thripidae):
Onion thrips is world-wide and is found throughout India as a major pest of onion and garlic {Allium fistulosam L.). It also feeds on many other plants, including cotton (Gossypium spp.), cabbage, cauliflower, potato, tobacco, tomato, cucumber (Cucumis sativus L.), etc.
Damage is done by adults as well as by nymphs. The adults are slender, yellowish brown and measure about 1 mm in length. The males are wingless whereas the females have long, narrow strap-like wings, which are furnished with long hair along the hind margins. In shape and colour, the nymphs resemble the adults but are wingless and slightly smaller. The insects are just visible to the unaided eye and are seen moving briskly on the flowers and leaves of onion and garlic plants.
Life-Cycle:
This pest is active throughout the year and breeds on onion and garlic from November to May when it migrates to cotton and other summer host plants and breeds there till September. In October, it is found on cabbage and cauliflower. The adult female lives for 2-4 weeks and lays 50-60 kidney-shaped eggs singly in slits which are made in leaf tissue with its sharp ovipositors. The eggs hatch in 4-9 days and the nymphs start feeding on plant juices by lacerating the leaf tissues.
On onion and garlic, they are usually congregated at the base of a leaf or in the flower. On cotton, cabbage and cauliflower, they generally feed on the lower surface of leaves. The nymphs pass through four stages and are full-fed in 4-6 days, after which they descend to the ground and pupate at a depth of about 25 mm. The pre-pupal and pupal stages last 1-2 and 2-4 days, respectively. Several generations are completed in a year.
Damage:
In onion and garlic, the leaves of attacked plants become curled, wrinkled and gradually dry up. The plants do not form bulbs nor do the flowers set seed. In cotton, the leaves become wrinkled and fall off and the plants bear very few bolls. In Hawaii, T. tabaci is known to act as a vector of the streak-virus disease of peas and yellow-spot of pineapple.
Control:
Spray 625 ml of malathion 50 EC in 200 litres of water per ha as soon as the pest appears. A waiting period of 7 days should be observed before harvest.
7. Onion Fly, Delia Antiqua (Meigen) (Diptera: Anthomyiidae):
The onion fly is widely distributed in France, Germany, Canada, USA, Japan, erstwhile USSR and England. This pest also attacks onions-in northern India. The flies are slender, greyish, large- winged, rather bristly and about 6 mm in body length. The maggots are small, white and about 8 mm in length.
Life-Cycle:
The female lays elongate, white eggs near the base of the plant, in cracks in the soil. The eggs hatch in 2-7 days. The maggots crawl up to the plant, and enter the inside of the leaf sheath and reach the bulb. They feed there and become full-grown in 2-3 weeks. The maggots then crawl out of the bulb and pupate in the soil. After 2-3 weeks, the adults emerge and start the new generation. In the third generation, the pest often attacks the onions shortly before the harvest. It initiates the process of rotting of the onions in storage.
Damage:
The maggots bore into the bulbs, causing the plants to become flabby and yellowish. They mine through the small bulbs completely, leaving only the outer sheath and thus causing a thin stand of the crop. At times, it destroys 8-9 per cent of the plants. The larger bulbs are attacked by several maggots at a time, making cavities. The attack is not completely destructive to the bulbs but it causes subsequent rotting in storage. It has been indicated that this insect causes the initial damage which leads to the development of soft rot of onion, caused by Bacillus carotovorus.
Control:
Apply 10 kg of carbaryl 4G or phorate 10G to the soil followed by light irrigation.
8. Pea Leafminer, Chromatomyiahordeola (Goureau) (Diptera: Agromyzidae):
This pest is widely distributed in northern India and feeds on a large number of cruciferous plants, antirrhinum, nasturtinum, pea, linseed (Linum usitatissimum L.) and potato (Solatium tuberosum L.). Only the larvae are destructive and they make prominent whitish tunnels in the leaves. If the attacked leaves are held against bright light, the minute slender larvae can be seen feeding within the tunnels. The adults are two-winged flies having greyish black mesonotum and yellowish frons.
Life-Cycle:
The pest is active from December to April or May and is believed to pass the rest of the year in soil, in the pupal stage. The adults emerge at the beginning of December and after mating, start laying eggs singly, in leaf tissues. The eggs hatch in 2-3 days and the larvae feed between the lower and upper epidermis by making zig-zag tunnels. They are full-grown in about 5 days and pupate within the galleries. The adults emerge from the pupae in 6 days and the life-cycle is completed in 13-14 days. The pest passes through several broods from December to April-May.
Damage:
The large number of tunnels made by the larvae interferes with photosynthesis and proper growth of the plants, making them look unattractive.
Control:
Spray one litre of dimethoate 30EC in 250 litres of water per ha and repeat spray at 15-day interval. A waiting period of 20 days should be observed for picking of pods.
9. Pea Stem Fly, Ophiomyia Pliaseoli (Tryon) (Diptera: Agromyzidae):
The pest causes damage in the larval stage. It is sporadic and is widely distributed in India, Sri Lanka, the Philippines, and China. It attacks peas, Phaseolus mungo L., Phaseolus aconitifolius Jacq., soybean, Glycine max Mer., cowpeas, Vigna catjans Walp and Lablab niger L. The larvae are leaf-and stem-miners. The adult flies are metallic black.
Life-Cycle:
The flies are active in summer and mate 2-6 days after emergence. The female lays 14-64 elongate, oval and white eggs into the leaf tissue with the help of its elongated ovipositor. The eggs hatch in 2-4 days and the maggots on emergence feed on leaf tissue at first but later on move to the terminal stems. They pass through three instars and the larval development is completed in 6-7 days in March-April and 9-12 days in November and December.
The larva pupates within its gallery and the pupal period lasts 5-9 days in March and April, and 18-19 days in November and December. The female flies live for 8-22 days and the males for 11 days. The pest completes 8-9 generations from July to April and shifts from one host plant to the other in various seasons. It passes winter as larva or as pupa.
Damage:
The maggots bore into the stem thereby causing withering and ultimate drying of the affected shoots, thus reducing the bearing capacity of the host plants. The adults also cause damage by puncturing the leaves, and the injured parts turn yellow. The damage is more severe on seedlings than on the grown up plants.
Control:
(i) Avoid sowing of the crop earlier than mid-October to check the attack of the pest.
(ii) Remove and destroy all the affected branches during the initial stages of attack.
(iii) Sow the crop in the second fortnight of October to escape the damage of the pest.
(iv) Apply 7.5 kg of phorate 10G or 25 kg of carbofuran 3G per ha in furrows at the time of sowing.
(iv) On the crop, spray three times 750 ml of oxydemeton methyl 25EC in 250 litres of water per ha. The first application should be just after germination and the other two at an interval of 2 weeks each.
10. Pea Aphid, Acyrthosiphon Pisum (Harris) (Hemiptera: Aphididae):
Pea aphid is cosmopolitan in distribution in both Palaearctic and Nearctic regions and has been recorded from practically all the areas where the peas are grown. Adult aphids are soft- bodied, long legged, pear-shaped, green yellow or pink in colour with long conspicuous cornicles.
Life-Cycle:
Both alate as well as apterous forms are present and these are generally females; males are rare. Winged and wingless males have been reported from Europe and USA but not from India. Reproduction is parthenogenetic and viviparous. It takes about a week to complete one generation and there are several overlapping generations in a year.
Damage:
Both nymphs and adults suck the sap from young shoots, ventral surface of tender leaves, inflorescence and even on stems. There is curling of leaves, which become irregularly distorted, while the shoots become stunted and malformed. The leaves turn pale and dry.
Honeydew secreted by the aphids encourages growth of sooty mould and this superficial black coating on leaves and stems hinders the photosynthetic activity of the plants, which become weak, thus affecting adversely the pod formation. Aphids are carriers of pea mosaic.
Control:
Spray 1 litre of dimethoate 30EC in 250 litres of water per ha when the attack starts and repeat after 15 days if necessary.
11. Pea Pod Borer, Eriella Zinckenella (Treitschke) (Lepidoptera: Pyralidae):
The larvae damage the crop by feeding on flowers and pods.
Control:
Spray 750 ml of endosulfan 35KG or 2.25 kg of carbaryl 50WP in 250 litres of water per ha when the attack starts. Repeat after 15 days if necessary.
12. American Bollworm, Helicoverpa Armigera (Hubner) (Lepidoptera: Noctuidae):
The damage is caused by the caterpillar by feeding on flowers and pods.
Control:
Spray 5 litres of chlorpyriphos 20EC or 2.0 kg of acephate 75SP in 250 litres of water per ha.
13. Red Vegetable Mite, Tetranychus Telarius Linnaeus (Acari: Tetranychidae):
The red vegetable mite, also called the two-spotted spider mite, is world-wide. In India, it is found in all the States and is very common in Bihar, Mysore, Rajasthan, Uttar Pradesh and Punjab. The large scale use of chlorinated hydrocarbon insecticides for the control of various other pests leads to the multiplication of mites, since they are less toxic to mites and especially since they kill large number of the natural enemies of mites.
The mite is a polyphagous pest and is known to feed on 183 species of plants including cucurbits, brinjal and okra on which it is occasionally very serious. The damage is caused both by the nymphs and adults. A large number of webs are formed on the leaves giving an unhealthy appearance. A fully developed nymph is microscopic and measures about 0.33 mm in length.
It is light brown and has two eye-spots, four pairs of legs and is quite active. The adult male measures about 0.52 mm in length and 0.30 mm in breadth. The body of the female is oval, pyriform and variable in colour. It may be ferruginous red, greenish amber or rusty green. Two large pigmented spots are present on the body.
Life-Cycle:
The mite is active from March to October and passes the winter as a gravid female. As the season warms up in March, it spins webs on the undersurface of leaves of various host plants and lays 60-80 eggs. The eggs are spherical and hatch in 2-6 days. The emerging larvae are light brown and have three pairs of legs.
They feed underneath the webs and, within 3-4 days; change into nymphs which have four pairs of legs. The nymphs grow to maturity in two stages within 4- 9 days and the adults live for 9-11 days. The life-cycle during the active period is completed in 9- 19 days. In Punjab, this mite is believed to complete 32 generations in a year.
Damage:
All the active stages usually feed on the underside of the leaves by sucking cell-sap. Gradually, the infested leaves dry up and the webbing interferes with plant growth. There is a poor setting of the fruits and the yield is considerably reduced.
Control:
Spray 625 ml of dimethoate 30EC or oxydemeton methyl 25EC in 250 litres of water per ha and repeat spray at 10-day interval.
14. Root-Knot Nematode, Meloidogyne Incognita Chitwood (Tylenchida: Heteroderidae):
This root-knot nematode is world-wide and is distributed throughout India. It is found with other allied species namely, M. javanica, M. arenaria, M. hapla and M. brevicauuda. It has been recorded on at least 45 host plants, including a number of economic crops and ornamental plants. It is a serious pest of vegetables such as brinjal, and tomato.
The root-knot nematode feeds on the roots of its host plants and forms galls on them. The attacked plants remain stunted and show symptoms of yellowing and shortening of the leaves. The appearance of flowers is also delayed.
Life-Cycle:
The gravid females of this nematode are always found in tissue inside the galls and they die there after laying eggs, which are oval and are found in yellowish clusters. A single female may lay as many as 768 eggs. The optimum temperature for hatching of the eggs ranges from 20 to 30°C.
There is no hatching during winter. In February-March, the larvae are liberated into the soil after the root-knots disintegrate. They live in the soil temporarily and ultimately reach the roots of host plants. They feed by making repeated thrusts into the cortex into which they enter eventually.
The larval stage is completed in 3 weeks and the females reach maturity in 33 days. It has been determined experimentally that pH of 7.1-7.25 is very congenial to the development and multiplication of this nematode. During the active period, many overlapping generations are completed on one crop or another.
Damage:
At the site of feeding, the internal tissues of the roots become modified to form galls. Sometimes, the galls also appear on other parts of the plant, which are above the ground. The typical symptoms of the disease caused by this nematode include the discoloration and shortening of the leaves, stunting of plants and, occasionally, their death. The diseased plants in a field can be spotted quite easily. The brinjal crop suffers more than other vegetables.
Control:
(i) The intercropping of okra with sesame reduces the attack of this nematode on the former crop.
(ii) Dip the roots of nursery plants in 0.03 per cent dimethoate for six hours before transplanting.
15. Cotton Jassid, Amrasca Biguttula Biguttula (Ishida) (Hemiptera: Cicadellidae):
The plants attacked by jassid show yellowing and curling along the margins, turn pale to bronze colour and finally premature defoliation occurs.
Control:
(i) Spray once or twice at fortnightly interval with 1.4 litres of malathion 50EC in 300 litres of water/ha.
(ii) As soon as flowering starts, give three sprays at fortnightly interval with 1.25 kg of carbaryl 50WP or 250 ml of fenvalerate 20EC or 200 ml of cypermethrin 25EC in 250-300 litres of water/ha.
(iii) For seed crop, apply 20 kg of phorate 10G at sowing in furrows or spray twice at fortnightly interval starting 15 days after sowing with 625 ml of dimethoate 30EC or 50 g of acetamiprid 20SP in 250-300 litres of water/ha.
16. Spotted Bollworms, Earias Insulana (Boisduval) and E. Vittella (Fabridus) (Lepidoptera: Noctuidae):
The shoots infested with borer droop downwards and dry up. The infested fruits have a varying number of holes.
Control:
(i) Plant resistant varieties, viz. Vaishali Madhu and Sel-6-1.
(ii) Remove regularly the attacked fruits and bury deep in the soil.
(iii) Uproot hollyhock and the ratooned cotton, which are host plants for bollworms.
(iv) Spray the crop when 20-30 per cent shoots show borer damage with 1.0 litre of monocrotophos 36SL or 250 ml of fenvalerate 20EC or 400 ml of deltamethrin 2.8EC or 200 ml of cypermethrin 25EC in 250-300 litres of water/ha.
17. Singhara Beetle, Galerucella Bimianica (Jacoby) (Coleoptera: Chrysomelidae):
The singhara beetle is widely distributed in Pakistan, Sri Lanka, Myanmar and India, and is a serious pest of water-nuts. So far it has not been recorded feeding on any other food plant.
Damage is caused by the grubs as well as by the beetles. The full-grown grubs are about 6 mm in length, the upper surface of the body being black and the lower surface being yellow. They are seen feeding on the upper epidermis of floating leaves. The beetles are about 6 mm long and 3 mm broad and are yellowish brown to dark brown, with black eyes and a large hump in the middle of the body.
Life-Cycle:
This pest is active throughout the year, although the speed of development is considerably retarded during winter. The beetles lay reddish-brown rounded eggs on the upper surface of leaves, in clusters of 6-10. The eggs are securely glued to the leaves. A beetle may lay, on an average, 254 eggs which hatch in 7-8 days and the grubs start feeding on the upper epidermis of the leaves.
They grow through 3 stages and become mature in 7- 22 days. Pupation takes place on the leaf surface and, like the eggs; the pupae are also firmly glued to the leaves. The pupal stage lasts 3-7 days and the adult beetles live for about a month; although some of them live up to three months. The life-cycle is completed in 17-37 days and there may be as many as 12-17 overlapping generations in a year.
Damage:
Both the grubs and adult beetles feed on leaves. Hence, there is an untimely drying up of the plants. The integument of the singhara fruits at the surface of the water may also be damaged and this results in rotting of the fruits.
Control:
The pest can be controlled by dusting the crop with carbaryl 5 per cent or malathion 2 per cent @ 25 kg per ha.
18. Sweet Potato Weevil, Cylas Formicarius (Fabricius) (Coleoptera: Apionidae):
This weevil is a serious pest of sweet potato in India and it also infests the allied species I. litoralis Choisy, I. learii (L.), I. purpurea (L.), I. prescaprae (L.),. I. trifida (L), I. trichocarpa (L.), I. paundurata (L.), I.palmata (L.), I. sepiaria, Calonyction aculeatum (L.) and Jacquemontia tamnifolia Gray. Both the grubs and the weevils bore into the tubers and make them unfit for consumption.
The adult weevils are small, 5.0-6.5 mm in length, bluish black in colour, with reddish brown prothorax and a long snout. The apodous grub is whitish with a brown head and is 8.22 mm long.
Life-Cycle:
The pest is particularly active during the rainy season, coinciding with the growth of sweet potatoes. The female weevil lays 97- 216 eggs in cavities made on the vines or the tubers. The oviposition period of the adults may range from 51 to 102 days. The eggs hatch in 3-7 days.
The grubs feed both on vines and the tubers, and the larval development is completed in 21-26 days. The pupation also takes place either in the vine or in the tuber. The pupal stage lasts 7-11 days and the life-cycle is completed in 36-43 days. More than one generation are completed in a year.
Damage:
It is a pest both in the field and in the storage. The weevils feed on leaves, vines and tubers, whereas the grubs bore into tender vines and tubers, making the latter unfit for marketing and consumption. Up to 60 per cent damage may be caused by the pest.
Control:
(i) Plant deep-rooted varieties.
(ii) Vines used for planting should be free from weevil infestation and infested portion should be destroyed.
(iii) No infested or rotting tuber should be left in the field after harvest of the crop.
(iv) Infestation may be minimised to some extent if the cracks in the field are closed by periodical hoeing.
(v) Spray 2.5 kg of carbaryl 50 WP followed by 2.0 litres of malathion 50 EC in 625 litres of water per ha.