Mastering six major measures can improve cocoon quality.

The poor quality of cocoon is directly related to the silk yield. The average silk yield of fresh cocoons in China has been maintained at about 11% for many years, while that in Japan is 19%. To investigate the reason, in addition to the cocoon collection and drying technology and silk reeling process have a certain influence, the key lies in the quality of the cocoon. The following aspects must be grasped in order to improve the quality of cocoons.

The selection of excellent silkworm varieties has a large amount of silk, high dry shell, high relaxation rate and stable characters. the selection of excellent silkworm varieties is the basic condition to improve cocoon quality. Attention should be paid to the climatic conditions of different silkworm periods in seed selection. Generally, multi-silk varieties with good cocoon quality are selected in spring, and only special varieties with medium or less silk weight and strong physique can be selected in summer and autumn or multi-silk and high-quality silkworm varieties both in spring and autumn. In a few mountainous areas the temperature is not too high in summer and autumn and spring varieties can also be properly reared in order to significantly improve the quality of cocoons. Spring silkworm Chunlei × Zhenzhu, 871 × 872, East China × Chunchen (Zhejiang), Jinlan × Minghui (Sichuan), 681 × 682 (Anhui), Xiang 7920 (Hunan) and so on are multi-silk silkworms, which have the advantages of large mulberry consumption, high leaf silk conversion rate, large cocoon shape, thick cocoon layer, high yield and so on. The summer and autumn varieties are 951 × 952 (Suzhou) and the spring and autumn varieties are Shu 63 × limit 16 (Sichuan). Rearing silkworm eggs for spring in summer and autumn has a silk yield of 4% to 5% higher than that of silkworm eggs in summer and autumn, and the income of each species can be increased by one or two hundred yuan. As the rearing resistance of spring silkworm eggs is weak in summer and autumn, measures must be taken to strictly disinfect, kill pathogens, select good leaves, prevent heat and cool down, in order to obtain a good cocoon harvest.

The nutritional composition of mulberry leaves is good, which is beneficial to improve the quality of silkworm cocoons. There are two mulberry populations: Lake mulberry and fire mulberry in Zhejiang and Jiangsu. Lake mulberry group generally has thick branches, large leaf shape, late hardening and strong adaptability, and most of them belong to mesophytic or late varieties; fire mulberry groups have red skin fire mulberry, white fire mulberry, their new shoots and tender leaves are purplish red, all belong to early varieties. Sichuan has Jiading mulberry in Leshan in southern Sichuan and crown mulberry in northeastern Sichuan. Jiading mulberry branches are long, sparse, with good leaf quality; crown mulberry branches are thin and straight, and the skin is bluish gray. Shandong has Lusang, with short and thick branches, dense nodes, early hardening and cold resistance. Guangdong has Guangdong mulberry, slender branches, small and thin leaves, early germination and weak cold resistance. There are Grusang in Shanxi, Huangsang in Hubei, Lisang 24 in Hunan, Baisang in Xinjiang and Xuanqiu No. 1 in Heilongjiang, which are all excellent types with regional characteristics.

Good mulberry is full and cooked, as the saying goes: a mouthful of mulberry leaves and a bite of silk. The full feeding of good mulberry in the big silkworm stage is the key to increase the cocoon silk weight, especially in the peak period of the fifth instar, it is necessary to ensure that the silkworm is full, so as to achieve the purpose of increasing the cocoon shell rate and dry shell weight. If the mulberry is fed or starved, the silk gland in the silkworm body is insufficient, the silk spitting is less, and the cocoon layer is thin, which will seriously affect the quality of the cocoon. Suitable ripening is another important factor to improve the quality of cocoon. If the silkworm is clustered too early, it will not eat enough mulberry and less silk, it will also increase the mountain silkworm, appear non-cocoon silkworm, and increase the proportion of yellow spot cocoon; the upper cluster is too late, the silkworm is too ripe, the silk is wasted before the cluster, and the silk is spun too quickly after the cluster. multiple cocoons, such as double-palace cocoons, firewood-printed cocoons, thin-skinned cocoons and deformed cocoons. In particular, the mixed clusters of green-headed silkworms (immature silkworms) and suitable-age silkworms are the most harmful, which is the main cause of yellow-spotted cocoons. Therefore, the upper cluster must be ripe, so that the initial maturity is old, prosperous ripening is green, and the abuse of ecdysone (catalyst) should be avoided.

Vigorously promote the cardboard square cluster cocoon cluster with square clusters, folded clusters, centipede clusters and so on. Square clusters (4.5 × 3 × 3 cm per hole) should be vigorously promoted, which has the advantages of one cocoon per hole, white cocoon color, good relaxation, and the cocoon rate is up to 98%, which is about 10% higher than that of other clusters. Because of good ventilation, low moisture content of cocoon layer and low adhesion of cocoon silk, it is easy to reel silk. Compared with the same batch of cocoons, 3A grade silk can be reeled with checkered cocoons, while only 1x 2A grade silk can be reeled with other clusters of cocoons. There are more secondary cocoons in the use of cocoons such as rapeseed straw and wicker branches, which should be improved. Strengthen the management in the cluster and pay attention to the greatest influence of exhaust ventilation on cocoon quality is temperature, humidity and air flow. The usual requirements for these three elements are: suitable temperature range 22-24 ℃, relative humidity 65%-70%, air flow 0.5-1 m / s.

Increasing the relaxation rate and the humidity and air flow in the cocoon cluster have the most obvious influence on the cocoon quality. reasonable measures must be taken to improve the relaxation rate and the cocoon rate. The methods are as follows: 1. Do a good job of dehumidification and ventilation in the first 3 days after the cluster, so as to achieve the purpose of drying at the silk outlet. 2. It is necessary to go to the high cluster, not the ground cluster. 3. It is necessary to put on thin clusters, not dense clusters. 4. The weather is sunny, open the doors and windows. 3. If the treetops do not shake, the cluster room should be ventilated. 4. Do a good job in the hygiene of cluster rooms to prevent the harm of insects and rats and prevent the spread and transmission of silkworm disease. In addition, for the middle and late autumn silkworms, it is necessary to do a good job of heating up because of the low temperature, so as to achieve the purpose of faster cocoon production, less residual silk and improve silk quality.

Selecting cocoons for sale should not sell unified cocoons, damp cocoons and hairy foot cocoons, and good cocoons and secondary cocoons should be sold separately. Cocoons should be put into baskets with straw handles inserted in the middle to facilitate ventilation. Cocoon packing in plastic bags is prohibited to prevent steaming and spoiling.

Sericulture is an early breeding project in China, but in the process of sericulture, the survival rate of silkworms is very important, but the quality of cocoons is also very important. I hope the above methods introduced by the editor can help some sericulture friends.