How to Improve Silkworm Cocoon Quality? Mastering Six Key Measures Is Essential

The quality of silkworm cocoons directly determines the silk yield rate. For many years, the average silk yield rate of fresh cocoons in China has remained at around 11%, while Japan's silk yield rate is 19%. The reasons, aside from the certain influence of cocoon collection and drying techniques and silk reeling processes, lie mainly in the quality of the silkworm cocoons. To improve cocoon quality, the following aspects must be addressed.

Select superior silkworm varieties Superior silkworm varieties have high silk content, high dry shell weight, high reelability, and stable traits. Selecting superior silkworm varieties is the fundamental condition for improving cocoon quality. When selecting varieties, pay attention to the climatic conditions of different rearing seasons. Generally, in spring, choose varieties with good cocoon quality and high silk content; in summer and autumn, only choose summer-autumn specialized varieties or spring-autumn dual-purpose high-silk high-quality varieties with medium or slightly low silk content but strong constitution. In a few mountainous areas where summer and autumn temperatures are not too high, spring-use varieties can also be appropriately reared to achieve the goal of significantly improving cocoon quality. Spring-use silkworm varieties such as Chun·Lei×Zhenzhu, 871×872, Huadong×Chunchen (Zhejiang), Jin·Lan×Ming·Hui (Sichuan), 681×682 (Anhui), Xiang 7920 (Hunan) and others all belong to high-silk varieties, with advantages including high mulberry consumption, high leaf-to-silk conversion rate, large cocoon shape, thick cocoon layer, and high yield. Summer-autumn use varieties include 951×952 (Suzhou), and spring-autumn dual-use varieties include Shu 63×Xian 16 (Sichuan). Rearing spring-use silkworm varieties in summer and autumn yields a silk rate 4%-5% higher than rearing summer-autumn use varieties, and each sheet of eggs can increase income by one to two hundred yuan. Since spring-use varieties have weaker stress resistance when reared in summer and autumn, measures such as strict disinfection, elimination of pathogens, careful selection of good leaves, and heat relief and cooling must be taken to help achieve a bumper cocoon harvest.

Plant superior mulberry varieties Mulberry leaves with good nutritional content help improve cocoon quality. Zhejiang and Jiangsu have two mulberry variety groups: Husang and Huosang. The Husang group generally has thick branches, large leaves, late hardening, and strong adaptability, mostly belonging to mid-season or late-season varieties; the Huosang group includes Hongpi Huosang and Baipi Huosang, whose young shoots and tender leaves are purplish-red, both belonging to early-season varieties. Sichuan has Jiating mulberry from Leshan in southern Sichuan, and Guansang from northeastern Sichuan. Jiating mulberry has long branches, sparse nodes, and good leaf quality; Guansang has thin straight branches and grayish-green bark. Shandong has Lusang, with thick short branches, dense nodes, early hardening, and cold resistance. Guangdong has Guangdong mulberry, with thin long branches, small thin leaves, early sprouting, and weak cold resistance. There are also Gelusang from Shanxi, Huangsang from Hubei, Lisang No. 24 from Hunan, Baisang from Xinjiang, Xuanqiu No. 1 from Heilongjiang, etc., all of which are superior types with regional characteristics.

Good mulberry, full feeding, and mounting on cocooning frames at proper maturity As the saying goes: one bite of mulberry leaf, one strand of silk. Full feeding on good mulberry during the late larval stage is key to increasing silk content; especially during the peak of the fifth instar, silkworms must be guaranteed full feeding to achieve the goal of increasing cocoon shell rate and dry shell weight. If mulberry is reduced or silkworms are starved before mounting, the silk glands in the silkworm body will be insufficient, spinning will be reduced, and the cocoon layer will be thin, seriously affecting cocoon quality. Mounting at proper maturity is another important factor in improving cocoon quality. Mounting too early means silkworms have not eaten enough mulberry, resulting in less silk content, increased wandering silkworms, non-cocooning silkworms, and an increased proportion of yellow-spotted cocoons; mounting too late means silkworms are over-mature, wasting silk before mounting and spinning too rapidly after mounting, producing more double cocoons, creased cocoons, thin-shelled cocoons, and deformed cocoons and other inferior cocoons. Especially when green-headed silkworms (immature silkworms) and properly matured silkworms are mounted together, the harm is greatest, and this is the main cause of yellow-spotted cocoons. Therefore, mounting must be at proper maturity, ensuring that early-maturing ones are slightly on the mature side and peak-maturing ones are slightly on the green side, while also avoiding the abuse of molting hormones (catalysts).

Vigorously promote cardboard square-mounted cocooning frames Cocooning frames include square frames, folded frames, centipede frames, etc. Square frames (each hole measuring 4.5×3×3 cm) should be vigorously promoted for cocoon spinning. Their advantages include one cocoon per cell, white cocoon color, good reelability, and a good cocoon rate reaching over 98%, about 10% higher than other frame types. Due to good ventilation, low moisture content in the cocoon layer, and low silk adhesion, reeling is easy. Comparing the same batch of cocoons, cocoons from square frames can be reeled into 3-4A grade silk, while cocoons from other frames can only be reeled into 1-2A grade silk. Using rapeseed stalks, willow branches, etc. for cocoon spinning produces more inferior cocoons, and improvements should be noted. Strengthen management during mounting. Pay attention to excretion and ventilation. The factors that most affect cocoon quality are temperature, humidity, and airflow. Generally, the requirements for these three elements are: suitable temperature range 22-24°C, relative humidity 65%-70%, airflow 0.5-1 m/s.

Improve reelability and increase good cocoon rate Humidity and airflow during mounting have the most obvious impact on cocoon quality. Reasonable measures must be taken to improve reelability and increase the good cocoon rate. The methods are as follows: 1. During the first 3 days after mounting, do a good job of moisture removal and ventilation to achieve the goal of drying as soon as silk is spun out. 2. Use high frames, not ground frames. 3. Use sparse frames, not dense frames. 4. When the weather is clear, open doors and windows. 5. When tree tips are not swaying, the mounting room should be ventilated. 6. Maintain good sanitation in the mounting room, prevent damage from insects and rodents, and prevent the spread and transmission of silkworm diseases. In addition, for mid-to-late autumn silkworms, because temperatures are relatively low, warming work needs to be done to achieve the goals of fast cocoon spinning, less residual silk in mature silkworms, and improved silk quality.

Select cocoons before selling Avoid selling mixed cocoons, damp cocoons, and hairy-footed cocoons; good cocoons and inferior cocoons should be sold separately. Cocoons should be placed in bamboo baskets with straw bundles inserted in the middle to facilitate ventilation. Plastic bags must not be used for storing cocoons to prevent heat buildup and deterioration.

Sericulture is a relatively early-established breeding project in China, but in the process of raising silkworms, although the survival rate of silkworms is certainly important, the quality of silkworm cocoons is also very important. We hope the methods introduced above by the editor can help some friends who raise silkworms.