A Survey and Control of Diseases of Silkworm, B. Mori in Punjab, NWFP, and Azad Kashmir

Abstract

Sericulture is a cottage industry in Pakistan and Azad Kashmir. During the last twenty years, diseases of B.mori have caused tremendous economic loss to poor villagers. Keeping in view the national importance of Sericulture in the country, Pakistan Science Foundation sanotioned a research project on the survey of diseases was initiated in February 1975. The results are briefly presented. At first, the rearing period of univoltine races of silkworm starts in the last week of February and continues up to the second week of May. In N.W.F.P the rearing period of univoltine races of B.mori starts in the first week of March and continues up to the middle of June. In Azad Kashmir, the rearing period of B.mori (univoltine races) starts in the first week of march and continues up to the end of June. There are various ecological zones in each province. There are fluctuations in the rearing period due to variation in temperature and humidity conditions of the areas concerned. The details of Morphology, Biology and Anatomy of B.mori were studied in the laboratory. Biology of B.mori were also studied in the rearing areas. Diseased eggs, leaves, cocoons, and moths were collected from all over the rearing areas. The time table of appearance of disease was investigated. In Punjab, diseases appeared in various areas (Multan, Pirwala, Chichawatni, Changamanga, Gujranwala, Sialkot, Gujrat, Daffar, Head Fakiria, Kahuta, Naushera, Taxilla, Hazro, Sargodha, Cambelpur, Hasanabdal, and Rawalpindi area). The diseases appeared during the first week of March and continue to cause a high mortality of larvae up to beginning of May. In N.W.F.P., disease appeared in various areas ( Peshawar, Mardan, Haripur , Bannu, Kohat, Parachiner, Miranshah, Swat, Dir, lower Chitral and upper Chitral) .The diseases appeared in epidemic form in the last week of April and out-break continued up to the middle of June. In Azad Kashmir, disease appeared in various areas (Mirpur, Afzalpur, Bhimber, Muzaffarabad, Hajera, Bagh, Kotli, khoeratta, Panjan, Tattapani, Panjera, Sehansa, Palendri, Tararkhel, Rawalkot, Leepa, Valley etc.) The diseases appeared in the last week of April and the epidemic continued up to the middle of Septemberer. Symptoms of diseases were studied in Larvae, pupae and moths. The pathogens were isolated from Larvae , pupae , Cocoons , Moths, eggs and rearing areas. Techniques were developed for quick pathological analysis and histopathology. The nature and extent of persistence of diseases was studied in various areas. In Punjab , during the period of 1975, 2nd, 3rd, and 4th instar larvae, pupae and moths had Nsema bombycis Infection. Nuclear polyhedrosis virus infection (NPV) was also spread in in 1975 and caused the deaths of millions of 2nd, 3rd and 4th instar larvae, pupae, and moths. In 1976, NPV infection developed in Changamanga area and Chichawatni area. In N.W.F.P., During the period of 1975, Nosema bombycis and Nuclear polyhedrosis virus caused a heavy infection in 2nd,3rd, and 4th pebrine. In 1976, Nosema bombycis infection was wide spread among the 3rd, 4th instar larvae pupae moths and eggs. Nuclear polyhedrosis virus and Nosema bombycis caused the death of millions of 3rd and 4th instar larvae. Thus cocoon productions was very low. Nosema bombycis was found in the majority of eggs and moths of various races of B.mori reared in Punjab, N.W.F.P, Azad Kashmir during the period of 1975 and 1976. Bacteria were isolated from diseased larvae, pupae, coocons, moths surface of eggs of B.mori, air of rearing room, coocons storage room and the dust of rearing rooms of all rearing areas. Pathogens and non-pathogenic bacteria were identified. Pathogenicity of bacteria was tested. A deadly pathogen, Bacillus thuringtensis was isolated from the dust of rearing rooms, rearing mats, larvae and pupae. Bacillus thuringiensis was found to be responsible for acute flacherid of the larvae. In Azad Kashmir, Proteus vulgaris and E.coli were associated with chronic flacherie developing in larvae, pupae and moths. Streptococci and staphylococci aureus were associated with septicaemia developing in the larvae, and pupae reared in Punjab, N.W.F.P, and Azad Kashmir. The site of development of pathogens in the larvae was studied. The histopathology of B.thuringiensis infected 3rd and 4th instar larvae showed that epithelial cells of intestine were attacked at 6 hours following infection. Adipose tissues and hypodermis were attacked within 24 hours following infection. Histopathology of other bacterial pathogens was studied. While studying the site of infection of nuclear polyhedrosis virus, histopathology of infected larvae showed that the nuclei of adipose tissues, tracheal membrane, dermal cells and blood cells developed polyhedral bodies within a week following infection. In general, NPV was a major casual agent of Grasserie. The life cycle and site of infection of Nosema Bombycis was studied. Extracellular stage, intracellular stage and stages in sporulation and spores in the mid-gut of new host were studied. Nosema Bombycis completed its life cycle in four to seven days after infection. Histopathological studies of 3rd and 4th instar larvae showed that Nosema bombycis developed heavily in epithelial cells, adipose tissues, silk glands, malpighian tubules, and hypodermal cells. The hypodermal cells of the larvae which were just before spinning, had a large number of Nosema bombycis. These late instar larvae showed dark pepper like spots on the integument. The pebrinized moths had patches. Discoloration of scales was also visible on the abdominal area of pebrinized moth. The moths, emerging from pebrinized cocoons, had deformed wings, distorted antennane and such moths layed scattered and clumped eggs. The infected larvae either died just before spinning or they span cocoons of very poor quality. Mostly, the cocoons were very thin, abnormal and stained. The fibre of such cocoons was very inferior. A thorough search was launched for tracing out various races of B.mori reared all over the country. The survey and laboratory studies showed that Chinese, Korean, Italian races and their hybrids have become susceptible to the disease in due course of time. Details of methods of determining diseases of B.mori were studied in sericulture grainage centres located at Murree, Khanasour, Rawalakot, and Tararkhel. It was noted that primitive storage conditions favoured the enhancement of disease “In Vivo”. Due to lack of technical Man power and scientific facilities, the disease were not determined on microbiological principles. This situation is prevailing since the last 30 years. Factors responsible for the dispersal and persistence of the disease were studied in all the ecological zones of rearing areas. Primitive rearing conditions were found to be responsible for out-break of diseases. House files disseminated the pathogens far and wide. The economic aspects of Sericulture is important to poor villagers. An amount of 30-35 seers of green cocoons may be obtained from one ounce of disease free B.mori eggs. However, 2-10% of eggs don’t hatch due to improper incubation and diseases. Diseased B.mori eggs, costing several millions of Rupees, are destroyed each year by Sericulture departments of Punjab, N.W.F.P., and Azad Kashmir. In 1975 and 76, millions of larvae died as a result of epidemic caused by Nosema bombycis, Nuclear polyhedrosis virus and bacterial pathogens. The surviving larvae span cocoons of very poor quality. Thus, the villagers had to suffer from 50 to 65% economic loss. Economic loss to rearers was very serious in Azad Kashmir both in 1975 and 76. Out of total distribution of eggs of B.mori, 5-10% did not hatch due to disease. During the rearing period, 30-100% silkworms larvae died in various ecological zones. The cocoon production was 35% less than the estimated yield. The total economic loss to rearers were ranged from 37% to 70% in various areas of Azad Kashmir. The cocoons were inferior and had a low quality of silk fibre. There is an urgent need for controlling the disease of B.mori reared all over the country. Poor people of the country are looking towards scientists, scientific organization and Pakistan Science foundation with a hope that scientific methods will be made available to them for controlling the diseases of silkworm.