Abstract

Young teak plantations in Kerala are affected by pink disease caused by Erythricium salmonicolor and outbreak of disease very often results in heavy damage to the stands. This short-term study an assessment of the disease situation in young teak plantations in different Forest Circles of the State was carried out to work out possible disease management measures. The study was carried out in selected 26 teak plantations of the age group 2-to 7-years-old in the Central, Southern and Northern Forest Circles of the State. Observations on disease incidence and severity, measurements of tree height, girth, etc. were recorded. Causal organism, Erythricium salmonicolor was isolated from disease specimens and growth studies were carried out. Fungicides, Calixin (Tridemorph), Contaf (Hexaconazole) and Fytran (Copper oxychloride) at different concentrations were screened against selected isolates of E. salmonicolor employing poisoned food technique.

High rainfall together with persistence of very high atmospheric humidity for a long period in the teak stands, possible high genetic variability and coexistence of genetically different strains of pathogen in the same locality are possible factors for high incidence, development, and fast spread of the disease. Presence of large stretches of plantations of Hevea brasiliensis, Acacia mangitim, A. auriculformis or Eucalyptus tereticornis on the peripheral areas of teak stands possibly influences the microclimate, especially the relative humidity of the area. As these plantation species are potential hosts of Erythricium salmonicolor, there is also possibility of existence of genetically different strains of pathogen and also build up of inoculum potential of the pathogen. Presence of heavy weeds and undergrowths in the teak stands further contributes in maintaining the conducive environment for the growth and development of the pink disease pathogen.

Results of laboratory screening of fungicides showed that both the systemic fungicides, Calixin 80 EC (Tridemorph) @ 0.01 % a.i. and Contaf 5 EC (Hexaconazole) @ 0.001 % a.i. are highly effective in arresting the colony growth of E. salmonicolor. The contact fungicide Fytran (Copper oxychloride) was also effective @ 0.3% a.i. For managing the pink disease in plantation, application of Calixin @ 0.1% a.i. or Contaf @ 0.001 % a.i. as spray on main stem will be effective. However, to avoid or reduce the incidence of pink disease in young teak plantations, the scheduled silvicultural operations including weeding have to be carried out rimely and promptly. Moreover, for achieving best result on disease management in teak plantation, more information on the genetic variability of pink disease pathogen and disease etiology is warranted.