The crop is damaged by several pests in the field and in storage, potato tuber moth often assumes a serious form causing huge losses.

Potato tuber moth
Phthorimaea operculella Zedler
Family: - Gelechidae
Order: - Lepidoptera

• Economic importance

This insect is not native of India but was first introduced in Bombay from Italy about 75 years ago. In India, it is reported in Uttar Pradesh, Maharashtra State, Bihar, and Punjab. It is serious both in field and storage but particularly more serious in storage. In the plains it is active throughout the year and passes its life cycle on potato plants in the fields from November to March as a leaf miner or boring into petioles, terminal shoots and tubers underground, and from April to November in storage. It has been said that 30-70% tubers get infested under indigenous methods of storage, but in bad case 90% damage is also reported in storage, if not properly attended. The temperature 86 to 1000F is found most congenial for the pest activity.

• Marks of identification

Moths are small narrow winged greyish brown in colour measure about 12mm long. Full grown caterpillars are pinkish white or pale greenish in colour and 14-20 mm long.

• Nature of damage

In early stage of the crop growth, the pest is injurious to the plant as leaf miner. It also bores into petioles and terminal shoots. The main danger is to tubers both in the field and under storage. The caterpillars bore the tubers and feed on the pupal as a result of damage the potato tubers rot. The presence of black excreta near the eye buds helps to detect its presence in the tubers. On cutting such tubers one can find the larva in the pulp.

• Life history

Eggs are laid singly near the eyes of exposed tubers and on the underside of leaves as well. A single female can lay 150-250 eggs. They hatch in 3-6 days. The larva become full grown within 2 to 3 weeks. Pupal period lasts for 7-10 days. The total period of life cycle is about 4 weeks. There are about 8-9 generations in a year.

• Host plants

The caterpillars are reported to feed on leaves of brinjal, tobacco and tomato in the field but potato tubers under storage are most vulnerable to its attack.

• Control measures

In field : -

1. Timely earthing up of the crop to cover the exposed tubers helps in reducing the intensity of infestation.
2. Two sprays with 0.05% quinalphos, 0.05% endosulfan or 0.1% carbaryl at 15 days interval starting 60 days after planting controls the pest effectively.
3. Heaps of harvested potatoes should not be kept exposed in the field but covered with straw and infested tubers should be rejected before storage.
4. Experience with Copidosoma koehleri B. an egg-larval parasite of potato tuber worm found to reduce the pest infestation by 50-55% when released at the rate of 20,000 mummies/ha at 7 days interval starting 45 days after planting.

In storage

1. The potatoes should be stored in well-ventilated cool and dry places with temperature not exceeding 210C.
2. Fumigate the tubers with CS2 at the rate of 1kg/27 cu.m for 48 hours at 700F or ethyl bromide at the rate of 1 kg/27 cu.m for the least three hours before storage. Cs2 is reported to induce sprouting in storage.
3. Covering of tubers with 1" layer of dry sand is stated to be a cheap and highly effective remedy against the pest
4. Walls of godown should be sprayed with 1% Malathion at an interval of three months.
5. Treatment of seed potato tubers with 5% Malathion at the rate of 125 gm/100kg is also reported to offer good protection against the pest. Such treated potatoes, however, should not be used for consumption.
6. If cold storage facilities are available, the produce can be safely stored for a longer period.
7. Synthetic insect pheromones are also being tried in the state.
8. Experiments of release of Copidosoma koehileri B. in storage.

1. Epilachna beetle
Epilachna dodecastigam M. Epilachna vigintio otopunctat F.
Family: -Coccinellidae
Order: - Coleoptera

• Economic importance

The adult beetles are good fliers and therefore, infest wide areas during active period.

• Marks of identification

The beetles are speical in shape pale brown in colour and motted with blackspots. The grubs are yellow with hairs on their body.

• Nature of damage

Both grub and beetle eat the chlorophyll of the leaf in between the veins and cause characteristic skeletonised patches on leaves.

• Life history

A female lays yellow coloured 120-180 eggs in batches of 30-25 eggs. Incubation period is 2-4 days, grub and pupal period are 12-18 and 3-6 days respectively. Entire life cycle is completed in 18-25 days in summer and extend upto 50 days in winter. There are 7 generations in a year.

• Host plants

It is polyghagous and damages tomato, bringal, karli, cucurbits etc.

• Control measures

1. Hand packing of grubs and collection of beetles by hand nets during early stages of at tack, helps in reducing the intensity of infestation.
2. 0.05% DDVP or endosulfan or Malathion spraying are also reported to be quite promising but have less residual effect.
3. Soil application with chlordane 5% dust or heptachlor 5% dust @ 50kg/ha.

2. Aphids
Myzus persicae Sulzer
Family: -Aphididae
Order: - Hemiptera

• Marks of Identification

Aphids are tiny yellowish soft-bodied insects, the adult is along 1mm long and has two projections called cornicles on the dorsal side of abdomen.

• Nature of damage

Aphids are found in large colonies on underside o leaves and tender shoots. The nymphs and adults suck the sap. Therefore, the affected leaves turn yellow, get wrinkled and destorted. The insect also exude honeydew on which fungus develops, rapidly covers the plant with sooty mould that interferes with the photosynthetic activity of the plant. As a result, the growth of plant is stunted and yield is affected adversely. Besides, they act as a vector for transmitting by aphds. The loss caused on this account is far more severe than by their feeding and devitalising the plant.

• Life history

Adults and apterous forms reproduce parthenogenitically. Single female produces 8-22 nymphs/day. The nymphs are completed in 7 to 9 days and several generations are completed in a season.

• Host plants

It is a polyphagous species have been recorded on cabbage, brinjal, radish, chilly, tomato, tobacco, sanhemp, sweet potato etc.

• Control measures

Spraying with 0.05% endosulfan, 0.02% phosphamidon, 0.03% dimethoate, methyl demeton or thiometon control the pest effectively.

3. Thrips
Helicothrips indicus Bagnall
Family: -Thripidae
Order: - Thysanoptera

• Marks of Identification

The adults are minute, delicate insects, less than 1mm long and are light yellow in colour. Wings have fringe or hairs throughout and hence they are called fringed, winged insects. The nymphs are still smaller, minute and wingless.

• Nature of damage

The adults and nymphs feed on leaves. They scrape the epidermis and such the oozing sap. As a result, light brown patches appear on infested leaves. The affected leaves curl and become dry.

• Life history

A female lays about 30-50 eggs in leaf tissues, which hatch in 4-5 days. Nymphal stage lasts for about 10-15 days. A generation is completed in one month.

• Host plants

Cabbage, cauliflower, knolkhol, groundnut, ambadi, brinjal etc

• Control measures

Spraying with 0.05% endosulfan, 0.02% phosphamidon, 0.03% dimethoate, methyl demeton or thiometon control the pest effectively.

4. Thrips
Hemitarsonemus latus Banks

• Marks of Identification

Mites are not insects as they have four pair of legs and belong to the class – Arachnida. They are extremely minute with variable colour.

• Nature of damage

They suck the cell sap from leaves. Badly attacked leaves show a peculiar bronzy and shiny appearance, ultimately wither and dry up.

• Host plants

Chillies, cotton, cluster bean, brinjal, bhendi etc.

• Control measures

1. Spray 0.2% sulphur or 0.03% dicofol,
2. Sulphur dusting at the rate of 20-25 kg/ha also gives satisfactory control of the pest.