Potato scab Potato scab (common scab)
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C.O.: Streptomyces scabies
Symptoms:
• Shallow and Dip lesion of scab
• Shallow scab affected superficial rough area corky tissue. Lesion wide size and shape.
• Dip pitted scab lesions are 1-3mm or more in death and darker and corky surface.
• The disease mainly affects young tubers
• Small, circular to irregular lesions on lenticels and periderm turning brown and rough
• Breaking of periderm and lesion become rough and depressed
• Tissues on periderm becomes corky
• Sometimes raised rough and corky pustules with 3-4 mm deep depression observed on tubers
• Above ground plant parts do not show symptoms
• Quality of tubers deteriorates and don’t fetch good price
Favorable condition:
• High soil temperature, 25-30C max. 40.5C
• Low soil moisture,
• High soil PH (alkaline)
Management:
• Deep ploughing in summer followed by green manuring with green gram or sunhemp in kharif.
• Crop rotation with legume crops.
• Addition of organic matters to enhance activity of Bio-control agent.
• Regular irrigation to maintain the soil moisture.
• use of acidic fertilizers like CAN (calcium ammonium nitrate).
• Use red skined cultivars like kufri Sindhuri
• Seed Tr. with boric acid3 5gm/10 l. solution for 30 min and drying.
Early blight Early blight:
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C. O. Alternaria solani (Ell.)and Martin
Symptoms:
• Disease appears before the initiation of tuberization
• Irregular brown to dark brown spots with concentric rings on lower most leaves
• Spots coalesces to form large patches but no white fungal growth observed on corresponding lower surface of leaves like late blight
• Entire foliage is blighted
• The fungus produces Alternaric acid
• May affect tubers near soil surface causing brown discoloration and dry rot
• Dark colored sunken lesions on stolen, stem and leaf petiole and defoliation of leaves
• Tuber infection in storage through infected tuber can cause considerable damage
• Number and size of tubers reduces.
Favorable condition :
• High temperature alternating with moist periods
• Frequent and heavy rains helps in abundant sporulation
• Optimum temperature 25 – 30 º C
• Poorly manured crops are more susceptible for disease
• Sandy soils where frequent irrigation is required.
Management :
• Use disease free seed tubers for planting
• Removal and destruction of infected plant debris
• Proper fertilization to maintain crop vigor
• Spray mancozeb @ 0.2% or captan @ 0.2% one week before disease appearance and repeat at 15-20 days interval
• Use tolerant variety – Kufri Sindhuri
Late blightLate blight :
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C. O.: Phytophthora infestans
Symptoms :
• Water soaked light brown lesions developed on leaf blade
• Lesions spreads over entire leaflet and petiole
• Lesions are roundish with concentric marking on the margin of leaf
• The lesions turn black and whitish fungal growth seen on lower surface of leaf
• Tuber infection causes dry rot and purplish brown discoloration
• Severely infected plants wilt within a few days
• Infected tubers starts rotting in storage which gives offensive odor
Favorable condition :
• Soil moisture 15-20 %, cool (12º – 15º C temp.) and
• Humid (91% R..H) weather with heavy dews or rains alternating with warm (20º C) moist period favors the disease development.
Management :
• Select healthy potato tubers for planting
• Seed treatment – dipping seed tubers in 1 % B.M for 30 min. before sowing
• Spraying mancozeb @ 0.25 %, or BM 1 %
• Spray ridomil– MZ 72 @0.20%
• Avoid injuries to potato at harvesting time
• Use resistant varieties i.e. Kufri Naveen, K. Jeevan, K.alenkar, K. Khasigaro , K. Moti, K.Kuber and K. Kishan
• Potato may be harvested 2-3 weeks after the death of crop.
Brown rot /Bacterial wiltBrown rot /Bacterial wilt
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C.O.: Burkholderia solanacearum
Symptoms:
• Infection takes place at any stage
• Wilting, stunting and yellowing of foliage
• Entire plant collapse
• Browning of vascular bundles (xylem)
• Brown ring is observed in the tuber
• Eye buds are blackened
• Bacterial ooze comes out of cut stem and tuber giving foul odor (unpleasant/ disagreeable smell)
• Badly infected tubers rot in field or even during sorting and grading.
Favorable condition :
• High temperature- 25-35º C
• Optimum PH. 6.2 to 6.6, maximum 7.4
• Organic matter promotes growth of bacterium.
Management :
• Follow crop rotation – 3 years rotation with maize, soybean and red top grass or two years rotation with potato-wheat.
• Collect and destroy infected plant debris from field
• Obtain seed tubers from disease free area
• Tuber treatment before planting with streptocycline @ 0.02 % for 30 min.
• Treat the cutting knives with rectified spirit or mercuric chloride 80% (1:500)
• Tuber dipping in B.M 1% (1kg :1kg: 100 lit water) for 30 min.
leaf rollPotato leaf roll:
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C.O.: Potato Leaf Roll Virus (PLRV)
Symptoms:
• Tips and margin of leaves roll upwards
• Midrib of leaves become spoon like and later funnel shape
• Leaf tips become yellowish and later brown
• The plant becomes stunted
• Necrosis of the phloem tissues
• Older leaves stiff, dry, become lathery and rolled like paper with pink to brownish margin
• Starch accumulation in affected plant observed
Management:
• As the virus is tuber borne, select healthy tubers for planting
• Use certified disease free seed tubers
• Remove infected plants and destroy them
• Destroy volunteer potato plants
• Spray 0.03% dimethoate or methyl-odemeton 0.03% for vector control
