**Management of Late Blight of Potato**

**Management of Late Blight of Potato**

Mehi Lal, Sanjeev Sharma, Saurabh Yadav and Santosh Kumar Santosh Kumar Additional information is available at the end of the chapter

Mehi Lal, Sanjeev Sharma, Saurabh Yadav and

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.72472

#### **Abstract**

Potato (*Solanum tuberosum* L.) is the most important crop and *Phytophthora infestans* (Mont.) de Bary is the oomycete, which was responsible for infamous Irish potato famine during 1843–45 and it continues to cause worldwide devastation of the potato. Moreover, this disease is re-emerging in the forms of different genotypes and causes huge yield loss in the potato crop. The factors which are responsible for huge yield loss of potato are applied improper management strategies and pathogen behavior. Management strategies includes; forecasting, cultural, biological, varietal and chemical management. Forecasting is the better option for management of late blight, if accurately forecasted and promptly information reaches to the end users. As infected potato tubers cause the primary sources of infection in next season. The cultural practices will also helpful in reducing inoculum load and managing the disease. The host resistance is best option for management of this disease. However, due to very divers' virulence nature of *P. infestans;* the resistance of the varieties is wiped out within a decade. Several fungicides including contact, systemic and translaminar have been evaluated from time to time; however, the pathogen has shown a remarkable capacity for change with respect to host genotype and fungicides. Nowadays biological control is gaining importance due to its eco-friendly in nature.

DOI: 10.5772/intechopen.72472

**Keywords:** potato, late blight, disease, management, fungicides, *Phytophthora*

#### **1. Introduction**

The Potato was originated in the hills of Andes and Bolivia in South America, subsequently it was introduced into Europe by Spaniards in the second half of the 16th century, from there it spread throughout Europe and rest of the world in the mid 17th to mid of 18th century. In Asia, particularly in India, it was introduced by Portuguese in 17th century [1]. The late blight fungus co-evolved with potato in Central and South America and subsequently spread

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© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons

to other parts of the world mainly through infected seed tubers. The late blight disease caused by oomycete, which was initially reported as *Botrytis infestans* in 1845 by C. Montagne, later on German scientist Anton de Bary renamed as *Phytophthora infestans* (Mont.) de Bary [2]. The entire potato crop across Europe, especially in Ireland, was killed prematurely during 1844–45; leading to worst ever famine the 'Irish Potato Famine' [3]. One million people died of starvation due to that famine and another million migrated to the USA and other parts of the world.

year in plain region with moderate to high disease severity. Variations in disease severity are mainly due to climatic factors i.e. rainfall, relative humidity, temperature and pathogen virulence. In Punjab (main potato growing belt), severe epidemics of late blight disease have appeared during 1985–1986, 1989–1990, 1992–1993 and 2006–2007 [21]. In 2006–07, average crop loss of 22% in productivity resulting in a net loss of around 0.16 mt of potato in the state of Punjab alone. The increase in disease severity could be due to a change in the pathogen population [22]. The varying degree of crop losses was also reported due to late blight from Punjab, Haryana, UP, Maharashtra Karnataka, Bihar and West Bengal [23]. The decline in productivity and yield of potato was in between 25 and 85% due to late blight, depending mainly on degree of susceptibility of the host plant [24]. The economic costs associated with late blight to be somewhere around US \$3–5 billion per year was estimated by several authors [25, 26]. A method had been used to conservative estimate costs of late blight and it was observed that lowest yields mainly in developing countries and previous eastern block countries which suffered over €10 billion per annum at least, whereas in developed countries with high yields

Management of Late Blight of Potato http://dx.doi.org/10.5772/intechopen.72472 85

(7.5% of global potato production) suffered damage of about €1 billion per year [27].

The late blight disease affects all plant parts especially leaves, stem and tubers.

Pale green water soaked spots (2–10 mm) appear mostly on the margin and tips. In moist weather, spots may appear anywhere on the leaves, enlarge rapidly and turn necrotic and black killing the entire leaf instantly. On the corresponding lower side, whitish cottony growth containing millions of sporangia forms around the dead area in a ring pattern (**Figure 1**).

Light brown lesions develop which elongates and encircles the stem and petioles breaking them and killing the plant/leaves instantly. Stem infection is more severe under high temperature and relative humidity conditions (**Figure 2**). Symptoms of stem blight are observed

Rusty brown discoloration of the flesh is the typical symptom of late blight (**Figure 3**). On outside tuber surface, hard depressions with purplish tinge on the sides are a common feature. Normally, late blight infected tubers are hard but associated secondary pathogens may set in

Generally, late blight appears on lower most leaves of the plant which goes unnoticed from a distance. Slowly, the disease spreads to the middle and then upper leaves. Subsequently it

**3. Symptomatology**

**3.2. Stem and petiole**

more in last ten years.

soft rot symptoms.

**3.4. Field infection**

**3.3. Tubers**

**3.1. Leaves**

The late blight disease was recorded in India for the first time between 1870 and 1880 in the Nilgiri hills [4]. Under subtropical plains particularly in eastern part of the India, it was first observed in 1898–1900 in Hooghly district of West Bengal [5]. In the northern part, it appeared for the first time in 1883 in Darjeeling and subsequently spread rapidly to other adjoining hills [6]. The late blight disease was observed in Khasi hills (North-eastern Region) in 1885, Kumaon hills in 1897 and in Shimla hills (North-western Region) in 1902 [5, 7]. During 1913, it appeared at several places in Assam and Bihar [6, 8–11]. In plains of Uttar Pradesh, it was reported for the first time in 1943 in Dehradun and Meerut [10]. Severe attack of the late blight was observed in Meerut district in 1949, 1950 and 1951 and subsequently in many other districts of Uttar Pradesh [12]. In Punjab, the disease was occurred annually from 1958 to 1963 except during 1961 [13]. Potatoes had been grown in Mahabaleshwar hills and other parts of Maharashtra but late blight was observed there only in 1973 [14]. In Gujarat and Madhya Pradesh, the disease was observed in traces in 1968 and in Rajasthan in 1958 [12]. Afterwards, appearance of late blight disease is regular feature with high disease severity in hill areas while in plains disease severity is moderate to high level.

#### **2. Crop losses**

*Phytophthora infestans* causes late blight diseases in potato and tomato crops worldwide. It is not cause only economic losses of yield but also the quality and quantity of the crop. It is a highly researchable pathogen in plant diseases. The worldwide late blight disease is reemerging, therefore this disease is constantly observed by the late blight researchers [15]. The late blight disease is considered emerging disease, it is not only having important in global crop production, but also pose severe risks on a local level, especially on small farms in developing countries [16]. The losses caused by late blight disease, it varied countries to countries, as per their adopted plant protections measures and grown cultivars. The yield losses due to late blight of potato were reported up to 50–70% during the 2007 under favorable environmental condition in Pakistan [17]; however recently Ahmed et al. [18] reported that late blight can induce 100% yield loss under epidemic condition in Pakistan. As far as Indian scenario is concerned, reduction in potato production due to late blight ranged between 5 and 90% depending upon climatic conditions, with an average of 15% across the country [19]. However, recently yield loss was reported, overall basis a range of 10–20% due to late blight in the year 2013–2014 major potato growing sites of the India viz., Uttar Pradesh, West Bengal, Punjab, Karnataka and Uttarakhand [20]. Whenever, disease appeared in epiphytotic form at early stage of the crop yield loss would be more. Tuber yield decline was significantly higher in unmanaged crop, which could go as high as 90% of total productivity in hilly regions. The changing climate pattern is being influenced appearance of late blight as it is occurring every year in plain region with moderate to high disease severity. Variations in disease severity are mainly due to climatic factors i.e. rainfall, relative humidity, temperature and pathogen virulence. In Punjab (main potato growing belt), severe epidemics of late blight disease have appeared during 1985–1986, 1989–1990, 1992–1993 and 2006–2007 [21]. In 2006–07, average crop loss of 22% in productivity resulting in a net loss of around 0.16 mt of potato in the state of Punjab alone. The increase in disease severity could be due to a change in the pathogen population [22]. The varying degree of crop losses was also reported due to late blight from Punjab, Haryana, UP, Maharashtra Karnataka, Bihar and West Bengal [23]. The decline in productivity and yield of potato was in between 25 and 85% due to late blight, depending mainly on degree of susceptibility of the host plant [24]. The economic costs associated with late blight to be somewhere around US \$3–5 billion per year was estimated by several authors [25, 26]. A method had been used to conservative estimate costs of late blight and it was observed that lowest yields mainly in developing countries and previous eastern block countries which suffered over €10 billion per annum at least, whereas in developed countries with high yields (7.5% of global potato production) suffered damage of about €1 billion per year [27].
