Research on shisham (Dalbergia sissoo Roxb.) decline in Pakistan - a review

This paper presents a review of literature of research carried out in Pakistan regarding the causes and possible control measures of recent shisham (Dalbergia sissoo Roxb.) decline in the country. Surveys of different regions of province Punjab reveal that shisham is suffering from two types of diseases namely wilt and dieback. Maximum mortality (up to 80%) was observed along the canal banks followed by (up to 40%) along the highways and roadsides. The least disease incidence and mortality rate was recorded on plants growing on agricultural lands and other well managed areas. Fusarium solani (Mart.) Appel & Wr. has been isolated from the roots of wilted shisham trees and confirmed as the causal agent of this disease. Causal agent of dieback is still controversial. Fusarium oxysporum, Ganoderma lucidum, Botryodiplodia theobromae and Phytophthora cinnamomi have been isolated from roots of dying back trees and are claimed to be the cause of dieback. Generally older plants are more susceptible to the disease attack than the younger ones. Stressed conditions especially drought and high soil moisture content are responsible for attack of pathogens and severity of the disease. In vitro toxicity assays with three fungicides revealed that Benomyl is the most effective in controlling mycelial growth of F. solani followed by Ridomil Gold. Field study showed that application of 50 liters of 200 ppm Benomyl solution can effectively recover 6-8 years old wilted shisham plants. Trichoderma species namely T. harzianum, T viride, T. aureoviride, T. koningii and T. pseudokoningii, and species of Aspergillus vie. A. fumigatus, A. glaucus and A. oryzae found effective in controlling in vitro growth of wilt pathogen F. solani. A great genetic variability exists in shisham in Pakistan. So far 18 different shisham varieties have been identified and there are many more which are yet to be identified. It is recommended that in future resistant and vigorous varieties should be planted on well-aerated sandy loam soil to save this precious tree species from being extinct in the country.