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Study on Integrated Diseases Management in Silkworm, Bombyx mori L. During

Unfavourable SeasonPREMANANDA NATH

PGDS TRAINEE, 2010-2011Roll No:105/SER/100026

E-mail: nath.premananda4@gmail.com

Dissertation Title

Central Sericultural Research & Training Institute Central Silk Board, Ministry Of Textiles, Govt. Of India

Berhampore – 7420101, West Bengal

Under the Guidance ofShri Zakir Hossain

Scientist- CSilkworm Pathology Section

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INTRODUCTION

Disease is a condition in which a state of physiological equilibrium of the host with the environment (i.e. health) becomes unbalanced.

Disease usually has a primary cause but there may be also be a complex web of secondary causes contributing to disease incidence (pre-disposing factors) including environmental conditions.

The major constraints in silk cocoon production are

the occurrence of diseases in silkworm.In India, the annual crop loss due to silkworm diseases is to an extent of 15-20% (Baig & Pradeep Kumar, 1987, Baig et al., 1990).

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In addition to different pathogens, viz. viral, bacterial fungal and protozoan, environmental and nutritional factors also play a significant role towards susceptibility of the host to infection and development of diseases.

No individual preventive measure is sufficient to check the disease incidence and hence an integration of several innovative measures have been developed for the management of silkworm diseases.

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OBJECTIVE OF THE STUDY

To study the predisposing factors for the cause of silkworm diseases.

To study the importance of different aspects of integrated disease management strategy towards prevention and control of silkworm diseases

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PREDISPOSING FACTORS CAUSING SILKWORM DISEASES

The predisposing factors responsible for

occurrence of silkworm diseases are:

Constitution of the silkworm Nutritional status Crowding Pathogen Load Environmental factors

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DIFFERENT ASPECTS OF INTEGRATED

DISEASE MANAGEMENT

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DISINFECTION

Disinfection means the selective elimination of undesirable micro-organisms. In sericulture it is the destruction or inactivation of disease causing germs. In sericulture, the commonly used disinfectants are formaldehyde, chlorine compounds, paraformaldehyde, slaked lime powder, etc., either individually or in combinations. Bed disinfectants such as Labex, Sericilllin, Vijetha, etc . are used. Disinfection is the single most important aspect of integrated disease management.

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IMPORTANCE OF HYGIENE

Due importance towards strict adherence to maintenance of hygienic conditions in and around the rearing house is a prerequisite for a successful cocoon harvest.

The hygienic conditions are summarized as:

Clean the rearing house and appliances of dust and dirt with water 5 days before brushing.

Sun dry the appliances in direct sunlight for 6 hours.

Sprinkle 5% bleaching powder in slaked lime surrounding the rearing house once in 2-3 days

Avoid injury to diseased larvae.

After bed cleaning, wipe the floor with 2% bleaching powder in 0.3% slaked lime.

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Provide optimum bed space and keep the bed dry.

Before entering into the rearing house, disinfect the hands by washing in dettol water or 2% bleaching powder solution in 0.3% slaked lime.

Disinfect the feet by walk over 5% bleaching powder in slaked lime on a foot mat at the entrance of rearing room.

Pick up diseased/ unequal/ suspected diseased worms before bed cleaning every day using forceps or chawki stick and dispose them into 5% bleaching powder in slaked lime in a basin.

Pick the diseased or dead larvae and flimsy cocoons from the mountage and burn them.

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1st inst. 2nd inst. 3rd inst. 4th inst. 5th inst.

Temp. (º C) 27-28 27-28 26-27 24-25 23-24

R.H. (%) 85-90 85-90 80-85 75-80 70-75

SILKWORM REARING MANAGEMENT

Location of Rearing House: Orientation of the room should be such that the interior is protected from the direct sunlight, as it is harmful to worms. The best orientation of rearing room will be north and south, the room should be with proper ventilation.

Env. Cond. of the Rearing House (Temp. and R.H.):The optimum Temperature and Humidity for Silkworm rearing

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Photoperiod:

Provision of 16 -18 hours of light and 6 - 8 hours of darkness in rearing room is essential.

Air:

The rearing room should be well ventilated to circulate fresh air.

Spacing:

The recommended spacing of rearing bed

Instar Spacing in Sq. ft.( for 100dfls)

I 6-18

II 18-54

III 54-100

IV 100-200

V 20-400 Contd…

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BED CLEANING:

Bed cleaning should be done with proper mesh size of net as per the stage. Recommended bed cleaning is once in 1st instar and twice in 2nd instar and from 3rd stage daily in the morning hours.

CARE DURING MOULTING

When 90% of the larvae settled for moulting no feeding to be given to worms. Slaked lime to be dusted to reduce bed humidity. Rearing bed maintained as thin to reduce bed humidity.

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MOUNTING DENSITY & ENVIRONMENT

The recommended mounting density for Multi X Multi hybrid is 60 larvae / sq. ft, for Bi X BI hybrid 40 larvae/ sq. ft, and for multi X Bi hybrid is 50 larvae/Sq. ft.

MOUNTING ENVIRONMENT

Proper environment in the mounting room should be maintained to get a good crop (24 - 25°C ,60 – 70 % R.H.).

HARVESTING AND STORAGE OF LEAVESHarvesting should be done during cooler hours of the day. The leaves should be properly preserved in leaf chamber, covered with wet gunny cloth. The leaf moisture could be retained by spraying water over the leaf at frequent intervals during summer

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SELECTION OF SILKWORM BREEDDuring favourable condition, under West Bengal condition it is advisable to rear Multi X Bi hybrids and during unfavourable condition Multi X Multi.

SELECTION OF IMPROVED MULBERRY VARIETY AND QUALITY OF LEAVESChoice of mulberry variety for silkworm rearing is very important for harvesting a good crop. S- 1 and S- 1635 is widely being practice by the sericulture farmers due to its qualitative and quantitative features. The mulberry leaf is the exclusive food of the silkworm Bombyx mori, L. and it is essential that mulberry leaves are good and of suitable quality for the silkworm. Leaf quality is the major contributor for the successful rearing and quality of cocoon produced.

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SILKWORM DISEASE SURVEY AND DISEASE SURVEILLANCE

Most of the silkworm diseases are season specific, henceForewarning system of diseases should be there for effective and timely management of diseases.

CONTROL OF MULBERRY PESTS

Incidence of different diseases in silkworm may be due to various sources of secondary contaminations including alternate hosts in and around mulberry garden.It is essential to control mulberry pests not only to increase the yield and quality of mulberry but also to prevent silkworm diseases.

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DISEASE DIAGNOSIS Early detection of silkworm disease is an important step in management of disease

Generally in silk worm develops their disease symptoms at the late stage of disease development

The period left between the development of characteristic symptoms and death is to short to adopt the curative measures.

Early detected of diseases during rearing and curative measure should be taken at early stage to avoid secondary infection.

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CONSTRAINTS IN MANAGEMENT OF DISEASES IN SILKWORM REARING

The major constraint in silkworm disease management is the need for a disinfectant suitable to the infrastructural facilities available with sericulturists

Most of the farmers do not have rearing houses as per required standard

Non adoption of required hygienic condition to be maintained during the course of rearing

Unavailability of technology which could diagnose disease incidence during early stage of infection.

A code of conduct for rearing of silkworm needs to be adopted to ensure survival of silkworm and to get good cocoon crop

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MATERIALS AND METHODS

For this study two rearings were conducted during July – September, 2011 (unfavourable season).There was one treatment and one control batch and each having 3(three) replications. After 1st moult 150 healthy worms for the 1st rearing and 200 worms for 2nd rearing for each replication in the treatment and control were selected. Two multivoltine breeds were taken for the study; Nistari (M) for the 1st rearing and M12 (W) for the second. Frequency of feeding was four times a day; at 6 am, 10 am, 4 pm and 8 pm.Labex was used as the bed disinfectant in the treatment and applied as per recommendation. Technology in respect to Package & Practices developed by Silkworm Physiology & RTI section of this institute was adopted for the treatment lot.

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RESULTS

Results from the two rearing conducted are depicted in Table 1, 2 and 3. The results showed that in the treatment, in which integrated approach towards management of silkworm diseases were adopted caused significant reduction in mortality due to diseases against the control in both the rearings conducted.

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Table: 1. Comparative Rearing Performance (July-Aug’11) Race: Nistari (M) Date of Brushing: 11.07.2011

Treatment/ Replication

No. of larva kept

Larval Mortality

(%)

Total mor-tality

(%)

Wt. of 10 matur.

larvae

ERR %

(by no)

Yield/ 100 dfls

(by No.)

Gra Fla Mus

Total

T

Rep- I 150 2.0 8.66 0 10.66 15.33 27.02 76 30400

Rep- II 150 0 6.66 0 6.67 12.0 26.67 81 32533

Rep-III 150 2.66 10.67 0 13.33 22.0 26.64 75 19866

Average 150 1.55 8.66 0 10.22 16.44 26.77 77 30933

C

Rep- I 150 10.67 11.33 0 22.0 30.0 24.63 63 25333

Rep- II 150 6.67 8.66 0 22.0 30.0 24.63 63 25333

Rep-III 150 8.0 8.66 0 16.66 23.33 25.62 66 26400

Average 150 8.45 9.55 0 18.0 24.66 25.38 66 26311 Contd…Gain % (by No) = 17.56 %

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Table: 2. Comparative Rearing Performance (Aug-Sep’11) Race: M 12 (w) Date of Brushing: 08.08.2011

Treatment/ Replication

No. of larva kept

Larval Mortality

(%)

Total mora lity

(%)

Wt. of 10 matured larvae

ERR %

(by No)

Yield/ 100 dfls

(by No.)

Gra Fla Mus

Total

T

Rep- I 200 0 9 0 9 12.5 22.98 60 23800

Rep- II 200 0 10 0 11 15.0 23.97 55 22000

Rep- III 200 1 8.5 0 8.5 13.5 22.20 51 20200

Average 200 0.33 9.17 0 9.50 13.7 23.05 55 22000

C

Rep- I 200 1.0 17.5 0 18.5 23.5 22.04 44 17600

Rep- II 200 0 19.5 0 19.5 26.5 21.64 45 18000

Rep- III 200 0 18 0 18 27.0 22.02 41 16200

Average 200 0.33 18.33 0 18.67 25.7 21.90 43 17267 Contd…Gain % (by No) = 27.41 %

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RESULTS

The reduction in total mortality (larval and pupal) was 8.22% and 12% respectively during the 1st & 2nd rearing.ERR was also higher in the treatment than in the control; 77 % in treatment against 66 % in control during the 1st crop and 55 % in treatment against 43 % in control during the 2nd crop. Yield gain (by No.) was recorded to be 17.56 % in the first crop and 27.41 % in the second crop. This difference in yield gain may be attributed to the difference in the two multivoltine breeds selected for the study and it may be inferred that during unfavourable condition M12 (W) is a better performer than Nistari (M). However post cocoon characters did not show any significant variation between the treatment and control.

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DISCUSSIONThe findings from our study are in agreement with those of Deviah (1986), Liu and Zhong, (1988). Results from our study revealed that higher ERR was achieved in the treatment against the control in both the crops conducted during unfavourable seasons. This was achieved by integration of not a single but a multitude of approaches viz. proper disinfection of the rearing room and appliances, use of bed disinfectant, spacing as per recommendations, selection of breeds for unfavourable season etc.Prevention is better than Cure” is the correct approach and that should be adopted in integrated disease control. This means that one should go about actively preventing disease before it occurs, and it is only when preventive measures are in force that we can hope to effectively control the occurrence and spread of disease.

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