Mulberry Root rot

Introduction

Root rot is a soil borne disease causing huge economic loss to the farmers due to its epidemic nature and potential to cause high mortality of mulberry plants. It is widely distributed in almost all the sericultural areas and mainly caused by the fungus Rhizoctonia bataticola (= Macrophomina phaseolina) and other opportunistic saprophytic microbes such as Fusarium solani, F. oxysporum, Botryodiplodia theobromae etc. The disease is very serious in mulberry growing areas of southern India. The disease occurs throughout the year in all types of soils especially when the soil moisture and organic matter are low. About 15 % loss is estimated due to the disease.

Symptoms

The disease appears in patches of the mulberry garden. Sudden withering of plants and leaves are the initial symptoms (Fig. 1). Leaves then start falling off from the bottom of the branches (Fig. 2). The root starts decaying due to the fungal infection (Fig. 3). Just below the root epidermis black fungal mycelia and spores are seen (Fig. 4). The severely affected plants lose their adherence to the soil and hence can easily be pulled out. The entire root system gets decayed and plants die.

Causal organisms

Rhizoctonia bataticola (= Macrophomina phaseolina)

Fusarium solani

F. oxysporum

Botryodiplodia theobromae

Pre disposing factors

The disease occurs in soils of high temperature (28 - 34ºC), low moisture (below 40 %) and low organic matter. The disease spreads primarily through contaminated soil, farm implements and irrigation. The secondary source of infestation is through diseased saplings, irrigation and cultivation practices.

Control

1. Cultural control

• Plough the infested land deeply and expose the soil to hot sun for effective killing of the pathogens. 
• Apply sufficient quantity of organic manure in the affected soil.

2. Chemical control

• As soon as the initial symptoms like wilting/ withering of leaves appear on shoots, apply Indofil M-45 around the root system @ 10 g/ plant after removing the soil from the infected plants to a depth of 15 cm.
• If the disease is very severe, uproot the affected plants and burn. Apply 10 g  Indofil M-45/pit in the it and plant the new sapling after dipping the root system in Indofil M-45 solution for 30 minutes. 
• Also apply Indofil M-45 to the surrounding plants of the diseased patch.
• Apply four doses of Indofil M-45 in a year at an interval of 3 months.

3. Integrated Disease Management:

         This method involves the application of both Indofil M-45 and biocontrol agent Trichoderma harzianum (Fig 15). Mix 1 kg Trichoderma harzianum with 50 kg FYM (for100 plants), store the mixture under shade, cover with gunny cloth and sprinkle water to keep the moisture content 20-30%. Keep the mixture for 15 days. The mixture may be tilted every alternative day. The Biocontrol agent Trichoderma harzianum grow and multiply in the FYM. The application of this mixture may be made as follows:

Uproot the diseased plants and burn.

This method does not have any toxic effect on both mulberry and silkworm. 

Apply 10 g of Indofil M-45 / pit and plant the new saplings after soaking in Indofil M-45 (0.1%) solution for 30 minutes.

After 15-20 days, apply the mixture @ 500g/plant in the root zone of the plant followed by irrigation

Continue application of this mixture for one year at an interval of 4 months.

Method of application:

1.          Prune off the dried shoots of infected plants above 15-30 cm from the ground.
2.          Make a shallow ring around stump by remove a little soil.
3.          Pour 1 litre Navinya solution made by mixing 10 g Navinya in 1 litre water (i.e. 1 kg Navinya in 100 liter water).
4.         The stump should be completely drenched while applying Navinya solution.
5.         Treat the surrounding mulberry plants also to prevent disease spread.

Precautions to be taken:

1.         Do not irrigate the treated mulberry plants during the first 4-5 days.
2.         Remove the dead mulberry plants and burn and expose the soil to sunlight.
3.         Plant the new saplings after dipping their roots in 0.2 % Navinya solution for 30
4.         minutes before planting.                                                                               

Related literature

Choudhari SS, Solanke NS, Kareppa BM, (2012) Integrated management of root rot disease of mulberry caused by Fusarium solani.  Multilogic in Science 2(2): 135-139.

Chowdary NB, Sharma DD, Mala VR, Nishitha Naik V, Kamble CK, (2009) Management of soil- borne diseases of mulberry through organic soil amendments. Indian Silk, September 2009, 22-23.

Chowdary NB, Sharma DD, Mala VR, Reddy MP, Kamble CK, (2009) Impact of Pseudomonas fluorescens  and Trichoderma harzianum in management of pathogen complexity causing root rot disease in mulberry. Sericologia, 49(2): 217-224.

Mandal SK, Biswas S, Teotia RS, (1993) Management of root rot disease of mulberry. Indian Silk April, 1992. pp. 43-44.

Manmohan MS, Govindaiah, (2012) Efficacy of botanical extracts against Fusarium oxysporum Schlecht causing mulberry root rot–an in vitro evaluation.  International Journal of Science and Nature, 3(2): 267-271

Naik, VN, Sharma DD Govindaiah, (2008) Incidence and intensity of root disease complex due to nematode and soilborne fungal pathogens in mulberry (Morus alba L.). Int. J. Indust. Entomol., 16 (2):  49-56.

Philip T, Sharma DD, (1997) In vitro evaluation of leaf and oilcake extracts of Azadirachta indica and Pongamia glabra on mulberry root rot pathogens. Indian J, Seric., 36(2): 150-152.

Philip T, Sharma DD, (1999) Antagonistic effect of Bacillus subtilis on mulberry root rot fungus Fusarium solani. Sericologia, 39 (2): 269 -272.

Philip T, Sharma DD, Govindaiah, Bajpai AK, Data RK, (1995) Root rot disease of mulberry and its management. Indian Farming, April-May1995. pp 23-25.

Philip, T, Sharma DD, Govindaiah, (1997) Fungal and bacterial association with root rot of mulberry. Indian J Seric., 36(1): 27-29.

Pratheesh Kumar PM, Naik VN, Shashank S, Sharma DD, Dayakar Yadav BR, (2012). Antagonistic effect of rhizosphere microbes against Fusarium solani- an associated pathogen of root rot diasese of mulberry. Indian J. Seric., 51(1); 11-15.

Pratheesh Kumar PM, Sharma DD,  Naik VN, Dayakar Yadav BR, Qadri SMH, (2010) Biofumigation- a recent approach for managing soilborne diseases in mulberry. Indian Silk, 1 (7): 6-7.

Sharma DD, Naik VN, Chowdary NB Mala VR, Kamble CK, (2009) Management of mulberry diseases through eco-friendly approaches- a review. Sericologia, 49(2): 123-138.

Sharma DD, Philip T, Govindaiah, (1996) Variability among five isolates of Fusarium solani causing root rot of mulberry.  Indian Phytopath., 49 (3):300-302.

Sharma DD, Naik VN, Chowdary NB, Mala VR, (2003) Soilborne diseases of mulberry and their management - a review.  Int. J. Indust. Entomol., 7(4): 93-106.