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The Early Blight of Tomatoes

Ailments and diseases are the cause of heavy losses in the tomato harvest

in the emirate of Abu Dhabi. The Early Blight is one of the diseases that are

considered as a big problem, threatening the tomato production in the

protected houses and open fields. The Early Blight is also called Alternaria

Solani, which is a fungal disease that affects all of the growth stages of the

tomato harvest and all the parts of the plant, except for the roots.

The quick spread of this disease often leads to the loss of the whole harvest

in few days. Hence, it needs immediate monitoring and effective combat,

using the integrated management methods for agricultural diseases. In this

booklet, you can get information on: (1) Symptoms, (2) Host and favoura-

ble conditions, (3) Early Blight Management

Introduction

Symptoms:The symptoms of the Early Blight includes:

Leaves: Uneven stains appear on the lower leaves, with circles that have a unified centre in the middle as well as yellow shades. At the time, the disease spreads to new leaves, the leaves that are already affected, turn totally yellow and they eventually fall.

Figures (1) & (2): The Symptoms of the Early Blight on the leaves.

Stem: Dark stains with a lighter centre and circles that have a unified centre may appear on the stem.

Figure (3): The Symptoms of the Early Blight on the stem.

Fruits: Skin-like stains that look like holes with circles that have a unified centre at the point of their convergence with the stem appear on the fruits.

Figure (4): The Symptoms of the Early Blight on the fruits.

Whole crop: The leaves turn yellow, then they become brown, and they eventually fall.

Figure (5): The Symptoms of the Early Blight on the tomato crop.

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The symptoms ofthe Early Blight

Second: The host and the favourable conditions for the Early Blight disease

The main host for the early blight disease is the eggplant crops (such as tomatoes, eggplants, pepper and potatoes),and pumpkin crops (such as cucumber, watermelon and courgette). Some herbs are considered as alternative hosts for the Early Blight. Moreover, the Early Blight can be transmitted through seeds, which would lead to withering. Moreover, the disease can be also transmitted via the remnants of the affected plants in the soil to the following season. Germs can also be formed on the surfaces of the affected tissues and they can spread through wind or water.The temperature and humidity of the leaf are two of the main factors that determine the rate of the spread of the disease. Germs need the humidity of the leaf surface to grow.The development of the disease and the production of new spores also need humidity. The rate of the spread of this disease is determined by temperature and humidity. The plants that are more prone to the Early Blight disease are the ones that have a 90%humidity rate and temperature ranging between 24-22 Celsius. The probability of being infected with the disease increases with the increase of the age of the plant, the growth of the fruits and the need for nutrients.

Third: Early Blight Management1- The protective methods in the open field

• Using the anti-early blight seed types if possible

• Using approved seeds that are void of diseases

• Using sound seedlings and avoiding overgrown or withering seedlings

• Installing irrigation systems in the permanent fields and maintaining them in a correct way, as well as curbing water waste from the broken pipes and sprayers so as to limit the humidity in the harvest area

• Adopting the agricultural practices that prevent water condensation and the formation of water drops so as to avoid the disease and limit its spread, as the installation of the [illegible] in the wrong way often leads to formation of condensed water on the leaves, and hence increase the probability of being affected with the Early Blight

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• Following a (four-year) agricultural cycle by inserting crops from the grasses family such as corn, where the Early Blight remains active for a full year, and so the germs can remain in the soil for several years

• Conducting solar sterilization for the soil during the summer season

• Removing the initial sources of infection such as grass and previous crops waste, and getting rid of them in a suitable manner

• Examining the plants regularly every two days to identify the Early Blight infection

• Removing the affected plants, getting rid of them by putting them in plastic bags, and sending them to the Waste Management Centre in Abu Dhabi

• Using sterilized and well-fermented organic fertilizers

• Balancing irrigation and fertilization while keeping suitable agricultural spaces in the manner recommended by the Abu Dhabi Agriculture & Food Safety Authority

• Providing the optimum conditions for the growth of the tomato crops and good fertilization management to maintain the vitality of the plants and to increase their resistance to the Early Blight disease

• Avoiding working on the plants in the early morning when the dew is on the surfaces of the leaves or when the weather is foggy or rainy

• Reducing the Early Blight infection by combating the insects that feed on the tomato crop, as the injuries that come from insects such as wounds, may increase the danger ofgetting infected with the Early Blight disease

•Combating the grass to provide good ventilation for the plants and eliminate the source of the initial infection

2- Protective methods in the protected houses

• Plant approved tomato types that resist the Early Blight diseases and use seedlings that are void of diseases

• Irrigate the plants in the morning or at noon as the tomato leaves are moist after the sunset and avoid irrigation at night

• Reduce the humidity level inside the protected house during the winter season by controlling the water of the air conditioner

• Examine the plants every two days to detect the Early Blight infection as the early detection eases combating the disease

• Monitoring the weather forecast to avoid the Early Blight, and if the expected environmental conditions are inducive for the spread of the disease, the farmers must spray their plants with fungicides before the infection

• Take special care of the plants in the areas where the sources of humidity are higher such as the areas close to the air conditioning system

• Monitor and fix the water leak in the protected houses

• Maintain suitable ventilation and air movement in the protected house, and maintain the relative humidity in a level that is less than %90

• Follow planting spaces in the manner recommended by the Abu Dhabi Agriculture & Food Safety Authority to ensure good air movement between the leaves and to keep them dry

• Follow the sterilization program of the protected houses and the tools used in pruning as well as the hands and shoes of the workers, to eliminate the sources of the disease, and that is through washing in a household bleach solution dissolved in water (9 parts of water to one part of bleach)

• Make sure to sterilize the soil

• Avoid irrigating the plants by spraying water in the air

• Remove the affected plants and get rid of the crop waste at the end of the season

• Reduce the chance of the plants getting infected with the disease by combating the insects, and controlling the movements of the labourers as well as by pruning the tomatoes

Biological Combat

The bacillus subtilis bacteria and trichoderma harzianum fungus can help prevent the Early Blight disease. These products are not poisonous for humans, animals and useful insects, and they can be used in a good way in the integrated anti-pests programs for managing the Early Blight disease.

Chemical CombatSpray protective fungicides when the environmental conditions are inducive for the spread of the disease. Most of the protective fungicides work by touch. Thus, comprehensive full coverage must be provided for all the plant parts that are prone to infection. After the growth of the plants and the production of new tissues, it may be necessary to spray protective fungicides from different chemical groups - if the conditions are favourable for the spread of the disease -, provided that these protective sprays do not exceed 3-2 times throughout the season. Fungicides can also be used as a treatment procedure when infection occurs.

See the table of the recommended fungicides

Table (1): Recommended Fungicides to Combat the Early Blight Disease

Before the harvest Fungicide Rate Fungicide*

3 days

7 days

7 days

7 days

7 days

75 mml to 90 mml/100 litres

250 mml to 300 mml/100 litres

150 grams/100 litres

50 grams/ 100 litres

150 grams/ 100 litres

Azoxystrobin

Fosetyl-AI

Copper hydroxide

Cymoxanil and Famoxadone

Propamocarb HCL

3100 90 75 Azoxystrobin

7100 300 250Fosetyl-Al

7100 150Copper hydroxide

7100 50 Cymoxanil and

Famoxadone

7 100 150Propamocarb HCL

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ترايكوديـرما هارزيامنسبتيليس )(( ) اÎصابةمبرضوفطر

(قائمة مبيدات الفطريات املوصى بها - انظر اجلدول)

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توصي به هيئة أبوظبي للزراعة والسالمة الغذائية لضمان حركة جيدة للهواء بني ا�وراق، واحلفاظ عليها جافة.

ميكنوتقليم

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هيئة أبوظبي للزراعة والسالمة الغذائية

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.حيـــث كمــا

من العوامل الرئيسة التي حتدد معدل انتشار املرض هما درجة حرارة الورقة ورطوبتها، حيث تؤدي رطوبة سطح الورقة إ� منو وتكاثر اجلراثيم. كما تسهم الرطوبة � تطور املرض وإنتاج أبواغ جديدة.وتعــد النباتــات ذات معــدالت الرطوبــة التــي تبلــغ %90 ودرجــات احلــرارة املªاوحة ما بــني 22 - 24 درجة مئويــة ا�كــ¹ عرضــة ل·صابــة مبــرض اللفحــة املبكــرة، كمــا توجــد هنــاك عوامــل أخــرى تزيــد مــن قابليــة

إصابة النباتات باملرض مثل عمر النباتات ومنو الثمار وزيادة االحتياجات الغذائية.

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تتحــول ا�وراق املصابــة مسبق� إ�إ� أوراق جديدةينتقــل صفراء بالكامل، ومن ثم تبدأ بالتساقط.

تظهــر

بداية تتحول ا�وراق إ� اللون ا�صفر، ومن ثم تصبح بنية اللون وبالتا� تبدأ بالتساقط � نهاية املطاف.

واحلقول احملمية البيوت � الطماطم إنتاج تهدد التي اخلط�ة ا�فات من املبكرة اللفحة مرض يعد املكشوفة.

تسمى اللفحة املبكرة أيض� ( التبقع البني) وهو مرض فطري يؤثر على كافة مراحل منو �صول الطماطم، كما أنه يصيب كافة أجزاء النبات ما عدا اجلذور. ويؤدي االنتشار السريع لهذا املرض غالب� إ� خسارة احملصول اªدارة طرق باستخدام الفاعلة واملكافحة الفورية املراقبة من البد لذلك جد³، قص�ة ف´ة خالل بالكامل

املتكاملة ل¶مراض الزراعية.

من خالل هذا الكتيب ميكنك احلصول على معلومات حول : 1. ا¸عراض

2. العائل الرئيسي والظروف املواتية3. إدارة مرض اللفحة املبكرة

مقدمة

اللفحة المبكرة فيمحصول الطماطم

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