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Measures and Methods to Prevent the Occurrence of Three-Molt Silkworms

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At present, most of the silkworms reared in our province are four-molt silkworms. Under normal incubation and rearing conditions, a four-molt silkworm should undergo four molts in one generation. However, if the incubation and rearing conditions are poor, a four-molt silkworm may undergo only three molts in one generation, resulting in reduced mulberry leaf consumption, smaller cocoon shape, and lower yield. The reasons why four-molt silkworms undergo only three molts include: incubation under low temperature, dry conditions and darkness at around 20°C; exposure to more than 12 hours of light per day during the young silkworm stage; feeding mulberry leaves that are too tender or too high in protein; after the silkworm eggs are brought back, they are not kept warm and protected, and are directly placed at natural temperature for supplementary incubation, resulting in excessively long supplementary incubation time and accumulated temperature failing to reach the standard;

At present, most of the silkworms reared in our province are four-molt silkworms. Under normal incubation and rearing conditions, a four-molt silkworm should undergo four molts in one generation. However, if the incubation and rearing conditions are poor, a four-molt silkworm may undergo only three molts in one generation, resulting in reduced mulberry leaf consumption, smaller cocoon shape, and lower yield.

The reasons why four-molt silkworms undergo only three molts include: incubation under low temperature, dry conditions and darkness at around 20°C; exposure to more than 12 hours of light per day during the young silkworm stage; feeding mulberry leaves that are too tender or too high in protein; after the silkworm eggs are brought back, they are not kept warm and protected, and are directly placed at natural temperature for supplementary incubation, resulting in excessively long supplementary incubation time and accumulated temperature failing to reach the standard; silkworms being exposed to high temperatures for a long time during rearing, and so on.

To prevent the occurrence of three-molt silkworms, the following five points should be done well: (1) Silkworm eggs must be ordered from the sericulture technology promotion and service department, that is, the main channel. (2) Supplementary incubation must be carried out as required. After the silkworm eggs are brought back, supplementary incubation should be carried out at a suitable temperature; the air must not be too dry, the humidity should be controlled at around 80%, and attention should be paid to dark protection. (3) Good management of mulberry orchard fertilization must be carried out, mainly with organic fertilizer and combining organic and inorganic fertilizers. Applying too much nitrogen fertilizer in mulberry orchards easily makes the protein content in mulberry leaves too high, and after silkworms eat such mulberry leaves, three-molt silkworms are likely to appear. (4) The quality of leaves must be strictly controlled, especially during the rearing of young silkworms; do not feed mulberry leaves that are too tender, and insist mainly on feeding leaves of suitable maturity. (5) Avoid long-term exposure to high temperatures above 30°C during rearing, and do a good job of heat prevention and cooling during hot weather.

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