Potato is the fastest growing major crop in
the developing world with important economic impact on many resource-poor
farming families. Potato (Solanum
tuberosum) is also an important stable food in high hills and the best
vegetable crop in mid hill and Terai (plain area) of Nepal (ABPSD, 2000).
Various kinds of problems are faced by farmers in the field, among them pest
(disease, insects, weeds etc) is one of them. Pest is the organisms which cause
damage to the human belongings (G.C and Keller, 2013). Many factors limit
production and profitability. Late blight caused by Phytophthora infestans (Mont.) De Bary is one of the most
devastating and destructive disease of potato worldwide (Hardy et al., 1995; Singh, 1996).  Subsequent outbreaks have been observed
almost annually and cultivars previously known to be resistant have become
susceptible to late blight disease (Ingliset al., 1996; Platt & Tai, 1998; Black et al., 1953).

Potato late blight occurs in most
potato-growing areas around the world, but it can be particularly devastating
in areas with warm and humid weather during the growing seasons (Hijmans et al., 2000).there might be total crop
loss to unprotected potato crop and yield losses majorly dependent on
meterological factors influencing severity ad incidence of disease (Crosier, 1934; Croxall & Smith, 1976; Hirst & Steadman, 1960a;  Zwankhuizen & Zadoks, 2002). Late blight disease
was first occurred in europe in 1940s ( (Fry et al., 1993) where reported in newspapers in finland since 1947(Mäkelä, 1966) and causing huge
loss.

 In the
same way it is the major problem which farmers of Kathmandu valley are facing as
production loss, unhealthy tubers etc. In high hills late blight occurs every
year with the significant yield loss whereas, in Terai the disease epidemic
usually occurs after 2-3 years causing substantial yield losses (NPRP, 2006).
one of the common practices against the disease outbreak is to apply protective
chemicals fungicides. In the high hills of Nepal losses have been encountered
more than 75 percent and in Terai losses have been reported 50-90 percent in
some years (Shrestha, 2000).

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To get more production farmers are primarily
using chemical pesticides which are environmentally non-degradable and costly.The
problems associated with the use of hazardous chemicals for plant disease
control has received increasing attention worldwide because it causes health
hazards, environmental pollution, pathogens become resistant to chemical
pesticides and ecological imbalances may occur (Fry, 1982; Bradshaw et
al., 2000). In recent years, there has been a growing
movement in the world to reduce the amount of synthetic pesticides being
applied to the environment as
according to a study, only one percent of the
total pesticide applied has become effective in controlling pests, remaining 99
percent goes into various environmental systems (Dhaliwal and Arora, 2001).
Botanical control is an alternative to chemical control that deserves
elaborative research (Maharjan
et.al, 2010). Many fungicides,
contact and systemic are available to manage the disease and farmers are using
them many times to protect their crop. (Bruck
et al., 1980; Evenhuis et al., 1996). There are other many ways to manage this disease like cultural
practices, resistant varieties use of botanicals etc. (Hermansen and
Naerstad, 2009; Roy et al., 2001; Bodker et al., 2006; Hannukkala et al., 2007,
Bhardwaj et al., 2005; 2007; Joseph et al., 2007; Kaushik et al., 2007; Joseph
et al., 2011; Bhardwaj et al., 2013)

In Nepal, when yield loss due to late blight is
estimated to a minimum level of 20 percent, the monitory loss reaches up to
NRs.1.8 billion annually (Sharma et al.,
2007). So various effective methods for the management of late blight disease
of potato should be applied and this paper helps to compare the effectiveness
of different control agent for late blight of potato like biological control
agent Trichoderma viridae, most
suitable fungicides which farmers are commonly using in Nepal and less costly
and easily available biological agent cow urine

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