| Chinese sericulture has a long history of 5,700 years.Ancient Chinese silk was one of the earliest and most important commodities in the export of the China government in any ages,remaining as a great concern to the masses and the state leaders.Therefore,the ancient Silk Road,the favorable policy of supporting sericulture as well as agriculture,and the existing’ East-to-West sericulture transfer project were launched one after another.With the implementation of the East-to-West sericulture transfer project,Yunnan Province has become a significant source area of high-quality silkworm cocoon in China.Large areas of silkworm rearing have been found in counties,districts and cities including Luliang,Xiongchu,Xiangyun,Heqing and Baoshan.Statistics from Luliang County,Qujing City,Yunnan Province in November 2012 showed that the county’s silkworm cocoon output exceeded 9,000 tons in the year,accounting for 22%of total output in Yunnan Province.In 2013,the output increased by 5,600 tons year-on-year.The increasing trend year by year is of great economic significance.The quality and quantity of silkworm cocoon are determined by a variety of factors.First,in order to improve the production efficiency,farmers usually abuse chemical fertilizers,which may lead to.a series of soil problems,such as accumulation of heavy metals and toxic elements,soil compaction and decreased activity of microorganisms,so as to affect the quality and quantity of crops(including mulberry).The second is climate factors.According to available data,the incidence of powdery mildew in early autumn is 50%and raises up to 100%in late autumn.The main source of nutrition for silkworms is subject to mulberry leaves,whose decline in quality and quantity will lead to a sharp drop in the survival rate of silkworm directly from 80～90%to 50%,or even lower.So it is the top priority to provide silkworms with adequate nutrition.In addition,the silkworm industry suffers great economic losses once the outbreak of epidemics.However,most silkworm drugs in the market are corrosive and residual,endangering the human body and destroying the environment.So it is badly in need of seeking an effective,natural,non-toxic and non-polluting agriculture chemical for the industry.Humic acid(HA),a macromolecular organic matter produced by a series of chemical and physical effects,such as biodegradation,transformation and geochemistry of animal and plant remains,is widely distributed and used in many fields.Main related products include organic fertilizer,pesticides,veterinary drugs,drought agents,feed additives,medicines,health products and cosmetics.Fulvic acid(FA)features the smallest molecular weight,the highest solubility and the highest biological activity in HA.It can be easily passive and absorbed by plants.In particular,it will be more water-soluble and active if it was transferred into fumarate.In recent years,it was reported that the efficacy of FA against bacterial,inflammations,virus and ulcer had been confirmed.In agriculture,it can also improve soil quality,promote fertilizer efficiency,stimulate crop growth,enhance plant resistance and improve crop quality.Meanwhile,the toxicity test data show that it has a low or even no toxicity.In conclusion,FA has a wide application prospect in medicine and agriculture.Recently,reports and literature showed that FA has a significant effect on inhibiting the silkworm pathogen Bacillus thuringiensis(B.t).In addition,it is worth mentioning that the application of FA and its fumarate in the management system of the silkworm industry has achieved preliminary results.In a word,the application of FA into mulberry plantation is of great significance.The HA and FA used in the experiment were collected by the degradation of Yunnan lignite via hydrogen peroxide,and achieved significant effect on mulberry cultivation and silkworm rearing.The main studies of the experiment are as follow:1 Construction of mulberry leaf quality protection system based on FA and its fumarate.It’s proved that mulberry leaves sprayed by FA and its fumarate thrive better with increased surface,crude protein content.No adverse reaction was found in silkworms fed with those mulberry leaves.The cocoon volume,cocoon layer and cocoon layer rate in the test area are higher than the control area.The experiment result indicated that FA and its fumarate can increase the yield of mulberry leaves and reduce the incidence of mulberry powdery mildew.2 Improving silkworms’ stress tolerance based on sodium fulvate(SF).It is known that FA and its fumarate can improve the body’s resistance.The researchers tested the objects’ resistance of hunger and 37℃ of high temperature.The result showed that SF can significantly improve the survival time of silkworm in hunger or the high temperature.3 Separation,identification of bacteria and virus in silkworms.Researchers collected flacherie,isolated and identified bacteria and viruses in the organism,and then used SF to make silkworm bacteriostatic experiment in vivo and in vitro to explore whether FA has the effect of directly inhibiting or killing bacteria in silkworms.The result showed that SF cannot directly inhibit or kill silkworm bacteria,but can improve the survival rate of silkworm and the cocoon output.4 Verifying the effects of SF on silkworm.The physiological indexes of silkworms were determined by adding silk FA directly into silkworms.The result showed that the FA could not improve their body weight,the amount of silkworm mulberry,the silkworm layer rate or the survival rate,but could significantly improve the silkworms’ cocoon output.The experiment showed that FA has a significant effect on silkworm mulberry cultivation and silkworm rearing.As a bio-organic fertilizer or foliar fertilizer,FA can improve the yield of mulberry leaves,reduce the incidence of mulberry powdery mildew.It indirectly improves the survival conditions of silkworms,their survival rate and cocoon output.As a feed additive or silkworm chemical,SF can be directly added into silkworms.It can not only improve the tolerance of silkworm,but also increase their survival rate,cocoon production rate and cocoon output,increasing farmers’incomes and improving silkworms’ economic benefits. |
