1. GRAPES POWDERY MILDEW
COLLEGE OF AGRICULTURALTECHNOLOGY
(Affiliated to Tamil Nadu Agricultural University, Coimbatore-3)
Kullapuram (Po),ViaVaigai Dam, Theni-625 562
STUDENT
Miss. DONGRE PRATHIMA
ID. No. 2015021033
COURSE TEACHER
Dr. PARTHASARATHY S
Asst. Professor (Plant Pathology)
3. Introduction
• Powdery mildew is an important disease of grapes worldwide.
• The disease generally is considered less economically important
than black rot or downy mildew.
• Unlike black rot and downy mildew, the powdery mildew
fungus does not require free water on the plant tissue surface to
infect.
• Powdery mildew can result in reduced vine growth, yield, fruit
quality, and winter hardiness.
• Varieties of Vitis vinifera and its hybrids generally are much
more susceptible than American varieties.
4. History
• The focus of this research is the invasion history and
population structure of the grape powdery mildew
fungus, Erysiphe necator (formerly Uncinula necator), an
obligate parasite of Vitis species that was introduced into
Europe and eventually, all other wine producing regions of the
world.
• Historical records support the hypothesis that the source of the
introduction is eastern North America .
5. • Powdery mildew was described on grapes in North America
in 1834, prior to its discovery in Europe in 1845 .
• Eastern North America is the centre of origin for many wild
species of Vitis that have relatively high levels of resistance to
many diseases and pests of grapevines, including powdery
mildew .
• After its introduction to Europe, grape powdery mildew was
observed throughout all wine producing regions of the world,
including California in 1859 and Australia in 1866 .
6. • Erysiphe necator most likely dispersed long distances by the
movement of grapevines, which were frequently traded
between continents in the mid 1800's and later.
9. Symptoms
• Malformation and discolouration of affected leaves.
• Discolouration of stem to dark brown.
• Floral infection results in shedding of flowers and poor fruit
set.
• Early berry infection results in shedding of affected berries.
• Powdery growth is visible on older berries and the infection
results in the Cracking of skin of the berries.
10. • It spread through air borne conidia.
• Through dormant mycelium and conidia present in the infected
shoots and buds.
13. Pathogen and its charcteristics
• Its cleistothecia have several asci & coiled tip appendages.
• Cleistothecia of the fungus are usually formed by fertilization
of ascogonia by anthridia during the sexual cycle.
• They become mature at late February or early March then
germinate by giving asci and ascospores inside.
• Ascospores will dessiminate by wind to reach the susceptible
organs for inducing infection.
• Asexual reproduction occurs by producing conidia that are
easily disseminate by wind, insects and workers from infected
plants to healthy plants.
15. Favourable Conditions
• Conidia germinate at optimum temperatures ranging from 10-
35 °C but temperatures from 25-28 °C low but not high
atmospheric relative humidity are necessary for mycelium
growth and conidial production.
16. Disease Cycle
• Powdery mildew is a polycyclic disease (one which produces a
secondary inoculum) that initially infects the leaf surface with
primary inoculum, which is conidia from mycelium, or
secondary inoculum, which is an overwintering structure
called a cleistothecium.
• When the disease begins to develop, it looks like a white
powdery substance.
• The primary inoculum process begins with an ascogonium
(female) and antheridium (male) joining to produce an
offspring.
17. • This offspring, a young cleistothecium, is used to infect the
host immediately or overwinter on the host to infect when the
timing is right (typically in spring).
• To infect, it produces a conidiophore that then bears conidia.
• These conidium move along to a susceptible surface to
germinate. Once these spores or conidia germinate, they
produce a structure called a haustoria, capable of "sucking"
nutrients from the plant cells directly under the epidermis of
the leaf.
18. • At this point, the fungi can infect leaves, buds and twigs that
then reinfect other plants or further infect the current host.
• From this point, you see more white powdery signs of
powdery mildew, and these structures produce secondary
inoculum to reinfect the host with mycelium and conidia, or
use the mycelium to produce primary inoculum to another
plant.
20. Integrated Disease Management
• Spray Wettable sulphur 0.25 % or Karathane 0.01 %.
• Select an open planting site with direct sunlight.
• Plant rows in the direction of the prevailing wind in order to
promote good air circulation and faster drying of foliage and
fruit.
• Prune and train vines properly in such as way as to reduce
shading and increase air circulation.
21. • Varieties differ greatly in their susceptibility to powdery
mildew. Cabernet Franc, Cabernet Sauvigon, Chancellor,
Chardonnay, Chelois, Merlot, Pinot blanc, Pinot noir, Riesling,
Rosette, Rougeon, Sauvignon blanc, Seyval, Vidal 256 and
Vignoles are all highly susceptible.
• On susceptible varieties, control is based on the use of
properly timed applications of effective fungicides. Early
season (prebloom through bloom) control of primary
infections caused by ascospores must be emphasized.
