One of the Major Diseases in Apples
Apple Scab- Venturia inaequalis

Monitoring the weather
An apple scab forecasting model.
Visual monitoring in autumn assessment of scab on fruit for the following year prediction.

Monitoring, Forecasting Model
Apple scab outbreaks can be predicted based on temperature and moisture conditions. The table below, derived from research by Mills and La
Plante, gives hours needed at various temperatures under constantly wet conditions for primary spores
(ascospores) to cause infection in spring.
An electronic apple scab forecasting unit

Mills, N.Z
)
Hours of wetness required for infection during spring
Average temperature
( °C)
Light infection
Moderate infection
Heavy infection
Days until lesions appear
0.5 - 5
10
15
18.9-23.9
25 .6
30
14
10
9
13
40
19
13
12
17
60
29
21
18
26
-
12
12
8
10

Prevention
Varieties incorporating scab resistance
Sanitation
Pruning and tree training
Leaf raking and urea
Control
Fungicides - cover spraying

Prevention, R esistant Varieties
Most currently available resistant varieties have a single gene that governs apple scab resistance.
Apple scab fungus easily overcomes the resistance
(similar to fungicide resistance).
Failure of resistant varieties has already occurred at some locations in Europe and the U.S.

Two Groups of Fungicides;
Protectant
Curative
Resistance
Among all groups resistance had appeared in different degrees.

Advantages Disadvantages
 Diseases are very slow to develop resistance to protectants.
 Effective against a range of diseases.
 On average, less expensive than curatives. •
 Superficial and can be washed off if rain falls within the ‘ -rain fast ’ period.
 Kill many fungi, including beneficial micro-organisms

Protectant Fungicides
Polyram (metiram)
Manzate Pro-Stick (mancozeb)
Dikar (mancozeb + dinocap)
Ziram
Captan 80%
Maestro 75 DF (captan)
Kumulus DF (sulphur)

Advantages Disadvantages


Less harmful than protectant fungicides to non-target fungi, including beneficial species.
Provide longer crop protection during prolonged wet weather.
 Fungal pathogens will become resistant following repeated application.

Curative Fungicides
Inspire (difenoconazole)
Nova (myclobutanil)
Nustar (flusilazole)
Sovran (kresoxim-methyl)
Flint (trifloxystrobin)
Pristine (boscalid + pyraclostrobin)
Vangard (cyprodinil)
Scala (pyrimethanil)
Senator (thiophanate-methyl)
Equal (dodine)

 The fungicides:
 Nova, Nustar, Inspire, Sovran, Flint, Pristine, Vangard and Scala are at risk for resistance .
 Note, Nova, Nustar and Inspire belong to the same class (sterol inhibitors).
 Sovran, Flint and Pristine belong to the same class
(strobilurins)
 Vangard and Scala belong to the same class
(anilinopyrimidine).

Panama Disease,
Caused by Fusarium oxysporum

Strains of F. oxysporum have been studied for more than 100 years.
The host rangeof these fungi is extremely broad, and includes animals, ranging from arthropods to humans, as well as plants.
Collectively, plant pathogenic F. oxysporum strains have a broad host range, but usually,only individual isolates cause disease on a narrow range of plant species.

The pathogen is resistant to fungicide and cannot be controlled chemically.
Panama disease is undoubtedly one of the most destructive plant diseases in modern times
It can spread with soil and water movement, and with movement of infected planting material.

It is a soil pathogen which infects the root system and goes on to colonise the plant through the vascular system – hyphae of the fungus can even reach the leaves.

Panama disease is considered to be one of the most destructive diseases of banana. It can spread with soil and water movement, and with movement of infected planting material.
It is a soil pathogen which infects the root system and goes on to colonise the plant through the vascular system – hyphae of the fungus can even reach the leaves. The disease cannot be controlled or cured other than by soil treatments, which unfortunately have such a detrimental effects on the environment that they are prohibited almost everywhere.

 the disease was first reported in
Australia in 1876.
In the 1950s, Panama disease wiped out the Gros Michel banana, the dominant cultivar of bananas, inflicting enormous costs and forcing producers to switch to other, disease-resistant cultivars.
 Panama disease is now found in all banana-producing regions except islands in the South Pacific, the
Mediterranean, Melanesia, and
Somalia.

Geographical distribution of Panama disease

The export banana industry was only saved by the introduction of the cultivar
‘ Cavendish ’ (AAA genome), which was resistant to F. oxysporum f. sp. Cubense
Outbreaks of the disease on ‘ Cavendish ’ in Australia, the Canary Islands, South
Africa (Ploetz, 1990) and Southern Asia
(O ’ Donnell et al., 1998) are threatening the continued use of this cultivar.
Cavendish lacks genetic diversity, which makes it vulnerable to diseases .

 Since the 1990s a new strain of the Fusarium fungus – the socalled Tropical Race (TR) 4 – has occurred and spread, destroying ten thousands of hectares of plantations of Cavendish bananas.
 Farmers in China, Indonesia,
Malaysia, the Philippines and
Australia are threatened in their business and livelihoods.

Using IPM methods for the control of
Fusarium oxysporum f. sp. cubense race 4 =
FOC

One control method is to improve soil conditions because
F. oxysporum spreads faster through soils that have high moisture and bad drainage

Intercropping and rotating banana with
Chinese chive can control Panama disease and increase cropland biodiversity.
Antifungal volatiles released from Chinese chive help control Panama disease in banana
Zhang H. et al. J.Chem. Ecol 2013 ole of plant volatiles.

Pseudomonas fluorescens
Bacillus subtilis
Trichoderma

Pseudomonas fluorescens is one of the major fungal biocontrol agents found in the soil, water and the rhizosphere of various crop systems.
It is an obligate aeroal, but certain strains are capable of using nitrate instead of oxygen.
P. fluorescens strains which present biocontrol properties, protect the roots of some plant species against parasitic fungi such as Fusarium or Pythium , as well as some phytophagous nematodes .

Theories how the plant growth-promoting properties of P. fluorescens are achieved:
1.The bacteria might induce systemic resistance in the host plant, so it can better resist attack by a true pathogen.
2.The bacteria might outcompete other (pathogenic) soil microbes, giving a competitive advantage at scavenging for iron.
3. The bacteria might produce compounds antagonistic to other soil microbes, such as phenazin, antibiotics type.

T. Saravanan et al. 2004, Plant Pathology Journal
Pseudomonas fluorescens isolated from banana rhizosphere reduced the vascular discolouration associated with Fusarium wilt disease and induced the accumulation of resistance associated enzymes in roots.
P. fluorescens treatment and challenge inoculation with the pathogen stimulated more enzymes accumulation in roots.
Peroxidase (PO) is a multipurpose enzyme that catalyses the condensation of phenolics into lignin and play specific role in the hypersensitive containment of the pathogen .

 A member of the genus Bacillus.
 B. subtilis has the ability to form a protective endosphore, allowing the organism to tolerate extreme environmental conditions.
 Although this species is commonly found in soil, more evidence suggests that B. subtilis is a normal gut commensal in humans.

Trichoderma is a genus of fungi that is present in all soils, where they are the most prevalent cultivable fungi.
Many species in this genus can be characterized as opportunistic avirulent plant symbionts.
Several Trichoderma species have the ability to form mutualistic endophytic relationships with several plant species.
The genomes of several Trichoderma species have been sequenced and are publicly available
Trichoderma colony in nature

Induced Resistance / (SAR=
Systemic Acquired Resistance
), in Banana Plants – with Pathogenic Strain of Fusarium oxysporum
(Janki Thakker 2013 ISRN Biotechnology )
 The present study strongly supports the view of preparation of plant vaccines for combating devastating disease like
Fusarium wilt of banana.
 Dead pathogen preparation was not only successful in mounting defense response but also in protecting plants upon subsequent infections. Therefore, it could be potential candidate for plant vaccine preparation to combat panama disease.