1. COLLEGE OF AGRICULTURAL TECHNOLOGY
(Affiliated to Tamil Nadu Agricultural University, Coimbatore-3)
Kullapuram (Po),ViaVaigai Dam, Theni-625 562
POTATO EARLY BLIGHT
Course teacher: Submitted by:
Dr.Parthasarathy.S, R.M. Sahanasree,
Asst. Professor, 2015021110.
(Plant Pathology)
3. Economic significance:
• Alternaria solani is also one of the most important foliar pathogens of
potato.
• In the U.S., yield loss estimates attributed to foliar damage, which
results in decreased tuber quality and yield reduction, can reach upto
20-30%.
• In storage, A. solani can cause dry rot of tubers and may also reduce
storage length, which both of which diminish the quantity and quality
of marketable tubers.
5. Symptoms:
• The symptoms of early blight occurs on stem, foliage and
tubers of potatoes.
• Small 1-2 mm black or brown lesions under conducive
environmental conditions, the lesions will enlarge and are
often surrounded by a yellow halo.
• Lesions greater than 10 mm in diameter have dark pigmented
concentric rings and there is formation of shot holes on tubers.
6. • As lesions expand, entire leaves may turn chlorotic
and dehisce, leading to significant defoliation.
• Lesions occurring on stem are often sunken and lens
shaped with a light center and have the typical
concentric rings.
• In tubers sunken irregular lesions which are often
surrounded by a raised purple border.
9. Systematic position
Kingdom : Fungi
Phyllum : Ascomycota
Class : Dothidiomycetes
Order : Pleosporales
Family : Pleosporaceae
Genus : Alternaria
Species : A. solani
10. Mode of spread:
• Primary spread : Infected plant debris.
• Secondary spread : Wind borne conidia.
Host:
• Tomato, Brinjal, and other members of Solanum family
11. Characters of Fungi:
• The fungi often overwinter as anamorphic stage and
sexual reproduction is rare.
• Mycelium is light brown, slender, profusely branched,
septate which are intercellular later become intracellular.
• The conidiophores are short, dark coloured and usually
undifferentiated.
12. • The type of conidia having transverse and
longitudinal septa is called as Muriform conidia.
• The tip cell of the conidium shows budding and
forms conidia in acropetal succession.
15. Favourable conditions:
• Warm, humid environmental conditions are
conducive to infections.
• The temperature favourable for its growth ranges
from 24-29º C.
16. Integrated Disease Management
Cultural Method:
• Avoid overhead irrigation.
• Late maturing varieties are more resistant than the
earlier maturing varieties.
17. • Do not dig tubers until they are fully mature in order to
prevent damage.
• Use adequate nitrogen levels and low phosphorus levels
to reduce disease severity.
• The variety Kufri Sindhuri possesses a fair degree of
resistance.
18. Chemical control
• The Protectant fungicides such as Mancozeb and
Chlorothalonil are the foundation of most early blight
management programs.
• These fungicides must be reapplied every 7-10 days to
provide protection of new growth.
• Very early spraying with Zineb or Captan 0.2% and
repeating it for every 15 – 20 days gives effective control.
