ABSTRACT
Citrus (Citrus sinesis L.) is one of the most important fruit crops known by humans since antiquity and is a good source of vitamin “C” with high antioxidant potential however there are various disease and pest that can affect the plant growth performance. Hence this study is aimed at assessing the various infectious diseases affecting citrus plant using orange as case study. The study revealed that Among the various toxicants viz., Agrimycin–100, Cupravit, Bavistin, Dithane M-45, Vitavax, Daconil, Antracol, Benlate and Nimrod tested at 1% concentration against multiplication of Xanthomonas campestris pv. citri. Agrimycin –100, Cupravit, Bavistin, Dithane M-45 and Vitavax proved more effective as compared to other toxicants In vitro. All the toxicants @ 1, 0.1 and 0.01% concentrations inhibited the multiplication of the bacterium however, Agrimycin-100 was found to be most effective while Cupravit, Bavistin, Dithane M–45 and Vitavax in that order, were effective against the multiplication of bacterium at 0.01, 0.1 and 1% concentration. Agrimycin–100, Cupravit, Bavistin, Dithane M-45 and Vitavax at 0.2% concentration were sprayed on the field grown citrus plants and then inoculated with Xanthomonas campestris pv. citri for the control of disease. Agrimycin–100, Cupravit, Bavistin, Dithane M-45 and Vitavax in the order proved effective also in reducing the disease intensity as compared to inoculated control.
CHAPTER ONE
INTRODUCTION
BACKGROUND TO STUDY
The present day citrus is delectable, juicy, and seedless and is of great nutritional significance as well. Additionally, it possesses enormous therapeutic qualities (Chaudhry et al., 1992). The prevailing climatic conditions in Nigeria are suitable for the successful cultivation of citrus (Syed, 2007). Kaduna is the centre of production and supply citrus fruits of high quality and grade worldwide. The major citrus growing areas in the Kaduna are Sargodha, Sahiwal, Jhang, Mianwali, Multan, Rahim Yar Khan and Toba Tek Singh, respectively (Govt. of Nigeria, 2009) but Sargodha is the dominant in citrus production holding enormous export potential as well. Being the major fruit crop of Nigeria citrus holds a key importance regarding export and as far as quantity is concerned Nigeria exports about 533 thousand tons of citrus (Govt. of Nigeria, 2011). Nigeria is considered as one of the largest producers of Kinnow. During 2010-11 the total area under citrus cultivation was 198.4 thousand hectares (ha) with total production of 2150.0 thousand tonnes (Govt. of Nigeria, 2011). At present, in Nigeria average production of citrus is 9.5 tons ha-1 (FAO, 2009) while the potential yield of citrus is 18-20 tons ha-1 which is almost half (50%) of the potential. So, there exists significant production gap between attained and potential yields.
Mentioned production gap is associated with several factors like most dominant factor insect pests and diseases. Batool et al. (2007) documented that citrus diseases has emerged as potential threat to citrus productivity globally. Likewise in Nigeria greening diseases is the major cause of citrus decline. Researchers further depicted diseases as graft transmissible, in nature, it is transmitted by psyllid vectors identified as Trioza erytreae (Del Guerico) in Africa and Diaphorina citri (Ku -wayama) in Asian countries.
Iqbal et al. (2009) identified that reduced technical efficiency of farmers leads them to no information about viral, pest related, air borne and soil borne diseases causing severe loss of orchards. Akhtar and Ahmed (1999) noted severe loss of citrus due to these diseases like 22% in Kinnow, 25–40% in sweet orange, 15% in grapefruit, 10% in sweet lime, and 2% lemon. Arif et al. (1962) highlighted the average incidence of citrus Tristeza Closterovirus (CTV) 27%, citrus variegation ilarvirus (CVV) 31%, citrus exocortis viroid (CEVd) 16%, citrus cachexia viroid (CCVd) 4%, citrus greening (Liberobacter sp.) 4% and stubborn (Spiroplasma citri) 2%, respectively. High incidence of these devastating pathogens has caused the severe citrus decline syndrome and drastic yield and quality losses in citrus fruits in the region.
Statement of problem
Diseases are not only identified in the Kaduna but also in other cities as well and citrus tristeza has been considered as major cause of decline (Bove, 1995). Preliminary survey conducted by a group of Italian and Nigeriai experts in 1988 with the co-operation of Ministry of Foreign Affairs and Nigeria Agricultural Research Council (PARC), citrus was reported to be infected by a number of virus and virus-like diseases in NWFP and Kaduna, Nigeria (Catara et al., 1988). Still at present situation is more adverse and most of the citrus orchards are about to collapse in Kaduna as about cent percent of citrus trees are infected with one or more virus and virus like diseases costing hue economic loss. The major virus and virus-like diseases of citrus trees reported in Nigeria are tristeza, infectious variegation, exocortis, cachexia- xyloporosis, greening and stubborn (Catara, 1987; Catara et al., 1988). Due to these inevitable circumstance farmers remain unable to manage the strike of diseases resultantly they obtain reduced production on farmers level and o country level production wise Nigeria is far behind as compared to other citrus growing countries of the world. By increase in cultivation area, better disease management, appropriate supply of nutrients, control on fruit disorders and several pre and postharvest techniques worlds other countries are getting per hectare yield almost double than Nigeria (UNCTAD, 2004) such as USA 22.41 tones ha-1, Brazil 22.38 tones ha-1 and Turkey 16.11 tones ha-1 (FAO, 2009). Although citrus crop is kept in large value, yet its present status is threatened by a number of problems, including low production caused by diseases. Citrus growers in Nigeria rely on chemicals for the control of citrus pests which poses negative effects on the beneficial insects (Giovanni, 1996). Due to WTO constraints, farmers have to rely on non-chemical methods. Citrus plant is attacked by number of diseases like citrus canker, gummosis, citrus decline, CTV, and greening etc. The low per hectare yield may be attributed to lack of effective control of insect/pests like citrus leaf minor, mealy bug, red scales, mites, termites, aphids and jassids, fruit fly and diseases like root rot, sudden death (quick decline of citrus), wither tip and citrus canker. These insects/pests and diseases not only affect the yield of citrus but also deteriorate the fruit quality. Lack of information about control of diseases and plant protection measures on the part of citrus growers are other factors that affect the production and quality of citrus fruit (Tariq et al., 2007). All these factors relate to adoption gap which is directly associated with the guidance provided by various extension agencies and other sources. A number of public and private agencies are involved in extension work (Ngomane et al., 2002). These are mainly responsible for dissemination of improved citrus protection measures among the citrus growers through varied approaches.
The broad objective of the research is to assess various infectious diseases affecting citrus plant using orange as case study. The specific objectives are thus:
1. To indentify the various pest and diseases affecting citrus plant
2. To examine the method of controlling these diseases
3. To profer solutions on strategies of preventing pest and diseases on citrus plant
1. To indentify the various pest and diseases affecting citrus plant
2. To examine the method of controlling these diseases
3. To profer solutions on strategies of preventing pest and diseases on citrus plant
Scope Of The Study
The work is limited to the examination of the various infectious diseases of citrus plants and the effect of pest and diseases on sweet orange (citrus sinensis).
Significance Of The Study
The result of this study will determine the diseases and pest that affect the quality of citrus fruits and plant. And if the results are favourable then consumption of sweet orange will be advocated, which is safer than consumption of medical drugs which often have side effect to the individuals taking them, As a preventive therapy (since it raises the immune system of the individuals involves). It is naturally safer to the sweet orange, which is a good item.
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