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Current Category » Introduction to Entomology

Lac-Culture, Its Hosts and Methods of its Inoculations

Lac is yet another useful product obtained from insects. Lac – culture is the cultivation of lac insects for the production of lac. The important lac producing countries are India and Thailand. The important centers in India are Bihar accounting 40 per cent of the country’s total production, Madhya Pradesh, West Bengal, Orissa, Assam and Uttar Pradesh.

Hosts for Lac – Cultivation:

The host plants of lac insects are Palas (Butea monosperma), Kusum (Schleichera oleosa) and Ber (Zizyphus mauritiana) are the three species commonly employed for lac cultivation throughout India. There are other species of trees which are used in particular regions like Crewia sp., Leea sp. and Cajanus cajan in Brahmaputra valley, Ficus sp. in parts of Assam, U.P. and Punjab and Shorea talura in Karnataka and Salem area of Tamil Nadu.

Strains of the Lac – Insect:

There are two strains of the Lac insect, the strain that thrives on Kusum is called Kusumi strain and the one that comes up on all other hosts is known as Rangeeni strain because of the deeper colour of the lac it produces. Both the strains have two generations a year. But the Rangeeni grown on Shorea talura in Salem area and Karnataka gives three crops in 13 months. About 90 per cent of lac produced in India comes from Rangeeni strain.

Seeds of Kusum tree are sown directly whereas those of other hosts like Palas and Ber are sown in nurseries and seedlings are transplanted. Though lac is cultivated under natural or jungle conditions, the lac insects prefer and yield better returns under orchards or plantation conditions.

Pruning and Cropping:

The lac hosts should have plenty of new growth with tender branches for feeding of the lac insect. Hence the trees can be pruned to get sufficient tender growth. As a separate process it is done before initial inoculation only but in subsequent years pruning is identical and one and the same as the cropping. Branches more than 2.5 cm in thickness are not cut, branches 1.25 cm or less in thickness are completely cut away at the places where they arise from the main shoots, while branches between 1.25 & 2.5 cm in thickness are cut leaving a stalk about 45 cm length. All the host trees should not be cultivated continuously with lac as this will have adverse effect on the vigour of the trees.

Introduction:

The time of inoculation and harvesting of different lac are:

Strain

Crop

Time of inoculation

With brood lac from

Time of harvesting

Rangeeni

Baisakhi

October
November

Katki crop

June – July

 

Katki

June – July

Baisakhi

October
November

Kusumi

Jathwi
Aghani

Jan – Feb
June - July

Aghani
Jathwi

June – July
Jan - Feb

Inoculation of various crops is done in the months as shown in the cropping calendar with the brood lac obtained from the previous crop of the particular strain. Brood lac should be cut from the parent tree when the lac cell is red in the anterior half and orange in the anal region. The brood lac should be thick and it should have continuous encrustation.

The selected brood lac branches are cut into sticks of 15 to 30 cm. They are tied by means of a banana or jute fiber either singly or in bundles of two or three sticks each and either longitudinally or interlaced between two host branches. Longitudinal inoculation allows maximum contact between the brood and the host. Inoculation has to be done on a non rain day. The alternate host trees like Acacia castechu Ougeinia oojeinensis and Moghania macrophylla are used to rear the brood for maintaining the vigor, similarly if two common hosts are available in a locality for a strain like Palas and Ber for Rangeeni, brood from one host can be used for inoculation the other.

One to 20 kg of brood lac sticks are necessary for inoculating a tree depending upon its size in the case of Kusumi strain and 0.4 to 5 kg in the case of Rangeeni strain. A heavier inoculation is not desirable as it may result in the death of the host tree.

The crawlers start moving out in one or two days after inoculation. The brood lac sticks need to be removed within three weeks of inoculation as otherwise the enemies of lac insect may spread from brood lac to fresh crop.

Cropping:

The crop is harvested earlier than the swarming is due but in the case of crop required for brood it is harvested later just before swarming is due to occur. The general symptoms of swarming are dried out appearance of encrustation two weeks before swarming and appearance of cracks on the encrustation at a later date. However, the appearance of an orange yellow area in the vicinity of the anal tubercle is the accurate indication for swarming. The crop for manufacture of shellac is spread out after harvest in a pucca floor without allowing them to stick together.

Yield:

Roughly 2.5 to 3 times the weight of brood lac can be expected as yield.

Natural Enemies:

Damage to lac crops may be due to both insects and causes other than insects, like monkeys, squirrels, rats, birds and lazards, adverse climatic conditions and bad pruning. The insect damage alone accounts for about 60 to 70 per cent loss.

Current Category » Introduction to Entomology