Sooty mould

Introduction

 Sooty mold is black, superficial growth of fungi especially on the leaf surfaces. The sooty mold results due to interaction of sap feeding insects and non – parasitic fungi. The fungi involved are saprophytic in nature, they do not invade inside the plant tissues, but remain on the surface. The fungi grow on honeydew excreted by sucking insects or on exudates from leaves.

In mulberry, sooty mould caused by pathogens such as Capnodium sp., Metacapnodium sp. and Euantennaria, have been reported with 90 % incidence from Anantapur during 1991. Further sooty mould caused by Chaetothyrium sp. and Curvularia affinis was reported in mulberry during November to February at Central Sericultural Research and Training Institute, Berhampore (Rao et al., 1992). The disease attained in devastating proportion in Malda, Murshidabad and Birbhum districts of West Bengal, India during 1998-1999 and caused panic among sericulture farmers.  Further, the sooty mold has been reported from Kashmir. The disease is found associated with sap sucking insects mainly white flies Dialeuropora decempuncta (Quaintance & Baker) (Fig. 1), Aleuroclavapentatuberculata  and small scale insect Parthenolecanium corni  Bouche (Hemiptera: Coccidae). The disease is very important since it can become epidemic within a short span if no control measures are done. The disease interferes with the photosynthetic activity of leaves and impairs the quality of leaves.

Symptoms

The disease appears in the form of a black powdery mass covering the entire upper surface. Presence of adult white flies or their nymph  in the garden which suck the sap from tender leaves resulting inchlorosis and leaf curl. The highly infected leaves fall off from the shoot.

Causal organisms

Capnodium sp., Metacapnodium sp. Chaetothyrium sp. and Curvularia affinis

Predisposing factors

             Incidence of whiteflies and other sap sucking insects are the important predisposing factor for the disease incidence. Among the biotic factors, previous 7 days of rainfall and maximum relative humidity are found responsible for the incidence of whitefly incidence.  The honeydew excreted by sucking insects serves as a balanced growth medium for fungi. Insect honeydews contain sugars, amino acids, proteins, minerals, and vitamins all are required for growth of the fungus.

Control

Management of whitefly is the only way to prevent incidence of sooty mould. Different methods such as biological, mechanical and chemical methods are recommended for the control of white fly.

Biological control: Release of 500 pairs of Brumoides suturalis per acresuppresses the population of whitefly population.

Mechanical control: Installation of  yellow coloured sticky traps @ 60 traps (2ft x 1 ft) per acre reduces the white fly infestation.

Chemical control: Spray of insecticides such as 0.02% Monocrotophos, 0.1% Dimethoate, 0.1% Dichlorvos or 1% Neem oil azadirachtin 1500ppm) is recommended.

Safe period

Two weeks (14 days) for both pesticides and Indofil.

Related literature 

Bandyopadhyay  U K, Santha Kumar MV,  Saratchandra B (2005). Role of insecticides and botanicals in regulating whitefly (Dialeuropora decempuncta) incidence and their influence on some economic traits of silkworm (Bombyx mori L.). Ann. Plant Prot. Sci., 13 (1): 48-53. 

Bandyopadhyay  UK, Sahu PK, Raina SK, Santhakumar  MV, Chakraborty N  Saratchandra B. (2000)  Studies on the seasonal incidence of the whitefly, (Dialeuropora decempuncta  (Q. & B.) causing leaf curl on mulberry in relation to abiotic factors. Int. J. Indust. Entomol., 1 (1):  65-71. 

Bandyopadhyay  UK, Santha Kumar MV  (2001-02). Studies on incidence of whitefly and its natural enemies. Annual Report, Central Sericultural Research & Training Institute, Berhampore, West  Bengal, India, Pp. 44-45. 

Bandyopadhyay UK, Santha Kumar MV, Das KK, Saratchandra B. (2001) Yield loss in  mulberry due to sucking pest whitefly, Dialeuropora decempuncta (Q. & B.) (Homoptera: Aleyrodidae).  Int. J. Indust. Entomol., 2 (1): 75-78. 

Irfan I, Aftab S, Mittal V Dhar A (2012). Sooty mold of mulberry – First report from Kashmir. Journal on New Biological Reports 1(2): 38-41. 

Rajkhowa G,  Chakravorty R (2004). Studies on the intensity and seasonal population variation of  whitefly, Dialeuropora decempuncta (Quaintance & Baker) on mulberry, Morus spp. in relation to abiotic factors. Indian J. Seric., 43 (2): 204-206. 

Reddy CR, Reddy PL, Misra S, Reddy KD, Sujathamma P, Reddy PR (2003) Sooty mould infection on mulberry –management. Intrl. J Industrial Entomology. 6(2): 203-205.

Santha Kumar MV,  Bandyopadhyay UK (2001-02). Biological control of whitefly.  Annual  Report, Central Sericultural Research & Training Institute, Berhampore, West Bengal, India, Pp. 46