Role of Nattrassia sp. In Fruit Orchard Decline and Determination of Key Factors for Its Management.

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.