Asian Research Thesis Index

Abstract

Decline of citrus mango and guava is a serious threat in Pakistan. This  study was undertaken to know the role of Nattrassia sp. in fruit orchard decline, its  biology and listing down the management strategies. Its role was studies through  recording the disease incidence and severity from citrus, mango and guava  orchards in Punjab from Sargodha, Bhalwal, Multan, Rahimyar Khan, Pattoki,  Sharqpur and Ahmedpur. Disease prevalence was found in all of the above areas of  citrus mango and guava with less or more intensities. The sampling from target tree  crops resulted in almost similar type of mycoflora except Ceratocystis sp. was  isolated from only decline affected mango trees. Other fungi include Nattrassia  mangiferae, Lasiodiplodia theobromae, Botryosphaeria sp., Fusarium sp.,  Cladosporium sp., Aspergillus sp., Penecillium sp. andCurvularia sp. with different  intensities from affected twigs, branches, stem at collar region and roots. However,  the fungus Nattrassia sp. and Lasiodiplodia sp. were the most common fungi.  Pathogenicity was conducted to know the four decline causing fungi including  Nattrassia sp. It was found that Nattrassia sp. alone cannot cause tree mortality but  contributes towards the mortality in combination with other fungi. The fungus  Nattrassia isolated from citrus is morphologically and physiologically different  from isolates of mango and guava. However, there is resemblance in isolates of  mango and guava. Most of the factors that favored the disease include no concept  of pruning; faulty intercropping; flooding of the orchards; application of partially  decomposed farm yard manure; poor nutrition; inadequate plant protection  measures and less interest of the growers. The orchards can be managed by  25   adopting pruning, following recommended plant protection plans, nutrition based  on leaf, soil and water sampling; avoiding plowing under tree canopies; if  necessary to intercrop choose friendly crops. In short the decline of citrus, mango  and guava have almost common, pathogens, common symptoms, common biology  and hence the common management strategies may be adopted to avoid them in  future.

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