Lessons from the stripe rust epiphytotic of Syria in 2010,facing false concepts

International wheat stripe rust symposium ICARDA, Aleppo, 18-20 Apr. 2011

Lessons from the stripe rust epiphytotic of Syria in 2010,facing false concepts

Fawaz AZMEH, Prof. of Plant Pathology, Fac. Of Agri. Damascus Univ. and National Commission for biotechnologyDamascus, [email protected]

mailto:[email protected]

Wednesday, April 12, 2023

A serious epiphytotic of stripe rust affected the Syrian wheat crop.

First alarms of intensive infection were signaled by farmers and agricultural services in February-March.

It could be estimated at this time that the fungus have already realized 3 or 4 uredinial generations to attain that degree of epidemic build-up.

What happened in 2010?

Wheat Stripe Rust Symposium, ICARDA


The disease affected mostly: Bread wheat (Triticum

aestivum) in northern, north-eastern and central syrian provinces.

High yielding modern cultivars (Cham8, Cham10… etc.)

High density seeded fields Irrigated wheat (more in

sprinkler watered fields?)

What happened in 2010?(cont.)



What happened in 2010? Epiphytotic favoring conditions:- Mild winter : During the 3 coldest months (Dec.+ Jan.+ Feb.)

temperature daily minima and maxima were 3-6 degrees above average in wheat growing areas.

- Frequent rainfall and high relative humidity: Until mid February rainfalls were above average in most agricultural zones.

- Consequent severe drought: A severe drought affected the region in spring time (March-April), aggravating the physiological damage of rust infection (synergetic effect of evapo-transpiration in diseased plants). Coincidence of these two factors may explain the very high levels of crop loss (50-80%) observed in some fields.



- Irrational agricultural practices:

-High (or very high) seed density (Syrian tradition !)

-Unorganized irrigation (side-effects of sprinkler irrigation)

-Mono-culturing of very few popular cultivars (Cham8 and others) in large areas.

-Unpreparedness for chemical intervention (fungicidal treatment). Syrian wheat farmers usually apply pesticides in very few cases:a. Seed treatment with fungicides for common Bunt (Telletia spp.)

b. Pre- or post- emergence herbicidal applications against broad leaf weeds, and rarely for wild oat (Avena spp.)

c. Insecticides in limited areas against Sunn Bug (Eurygaster integriceps).

- No previous experience in Syria of foliar treatment in wheat fields for fungal diseases.



- In addition to all these disease favoring conditions, the arrival and establishment of a new pathotype(s) of stripe rust, highly virulent to most popular bread wheat cultivars has been most probably the decisive factor.



Effect(s) of erroneous concepts: Crop losses due to stripe rust in 2010 could have been

minimized if immediate measures have been taken. Such prompt reaction was hindered by a series of erroneous

ideas about the nature of the problem and control strategies. As it is impossible to apply genetic (varietal resistance) or

change plant density during the season, the only available weapon left was chemical control (fungicide application).

Or, several contradictory opinions

were launched by specialists and

non-specialists, resulting in some

confusion on the farmers’ level.



Error 1: Stripe rust would not cause significant large scale crop loss, based on the fact that the disease has been observes since decades without causing important crop damage.

Result 1: It is now largely recognized that about 1.5 to 2M ton of wheat have been lost in 2010. If other damaging factors (frost, drought, Sunn Bug) the crop loss attributed to stripe rust alone could be estimated to 1M ton, representing #1/4 of the expected crop.



Error 2: Disease development/increase would spontaneously stop by early April (drier and warmer weather). This idea, based on former long term averages, could have been exact if chaotic climate changes, observed during the last decade are not considered.

Result 2: The weather continued after mid-April (and even in May) to be rather cold and sporadically rainy, permitting new disease cycle(s). These late infections attained the flag leaf and even the spike in many fields.



Error 3: fungicidal foliar treatment is either inefficient or uneconomic based on the absence of previous experience to control rust fungi. It has been said that either:

1) Fungicides are useless to stop the disease

2) Or their application is not economically justified.

Another pretext to explain the non-intervention policy is that adequate anti-rust fungicides were unavailable on the market or have not been registered for this purpose in Syria.



Result 3: only few farmers were able to apply fungicides. Some of them obtained good/very good results. Others were less lucky probably because of using inappropriate fungicides or bad application method or timing.

For the actual season (2011), reasonable quantities of selected fungicides (essentially triazoles) have been made available.

Farmers are now advised to apply fungicides whenever disease appeared and weather conditions are favorable.

On the other hand, it is clear that such application-if effective- is reasonably economic, especially when a high yield per hectare is expected (the cost of one treatment/ha is estimated to # 60$, which is the local price of about 250kg grain).



Error 4: No forecasting systems are available for rust disease, because the conditions of their development could not be subject to accurate modeling/simulation.

Result4: Since the 1970s, disease progress algorithms and epidemic models began to be developed for wheat diseases in general and yellow rust in particular (F. Rapilly, 1991)*

Several models and softwares are now available, based on fundamental knowledge of disease biology, in relation to weather conditions such as leaf wetness period, necessary to produce infections, under different temperatures.

*Epidemiologie en pathologie vegetale: Mycoses aeriennes.



In fact, the plant protection service purchased 8 forecasting systems, to be placed in different agricultural zones, destined mainly to warn about yellow rust risk.

All-round agrometeorological climate station supporting in total 14 sensors:

• 3 Temperature Sensors• 2 Relative Humidity Sensors• 2 Leaf Wetness Sensors• 1 Day Length Sensor• 1 Rain Gauge• 1 Solar Radiation Sensor• 1 Wind Speed Sensor• 1 Wind Direction Sensor• 1 Barometric Pressure Sensor• Soil Moisture SensorMETOS® Compact is supporting remote data access via:• Serial Cable • Land Line Telephone• GSM Telephone• Radio



Conclusions:

During this season(2011)most of the bread wheat fields have been seeded also with susceptible cultivars (Megavarieties). Resistant genotypes are still unavailable in needed quantities (not released yet or under seed multiplication).

The level of awareness for wheat rust diseases is now very high. Training for visual detection have been promoted by plant protection and extension services.



Stripe rust has been observed in several fields in different zones during March. This late disease start may indicate that the fungus was not able to over-summer or survive in wheat fields, nor to pass by a local alternative host.

Chemical control is now recommended and generally applied soon after disease detection and the situation seems to be under control.

Forecasting/warning systems are installed and tested. They should become operational for the next season (2012).

Procedures to register and import new pesticides have been accelerated and simplified following the stripe rust crisis of 2010.



Recommendations: The establishment of emergency plans for eventual

explosions of main diseases/pests on strategic crops (wheat, cotton, sugar beet, potato…)

reinforcement and acceleration of the national breeding program to create more cultivars with emphasis on testing for resistance, including under artificial disease pressure.

A reform of agricultural high education with emphasis on training broad-spectrum, field experienced plant breeders and phytopathologists.



Rust fungi: other aspectsRust fungi are not only fearful threats to agricultural crops. Only few of them are in this category.

In a broader view, rusts are a wonderful groups of species, at the top of the pyramid of fungal natural evolution, and a great lesson of biodiversity and plant-parasite interactions, and a good source contemplation and artistic inspiration !

Phragmidium violaceumSphaerophragmium milletiae vienn. Bourg.

Puccinia asphodeli

Photos: F. AzmehWheat Stripe Rust Symposium,

ICARDA


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Lessons from the stripe rust epiphytotic of Syria in 2010,facing false concepts

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