اعلانات هامة

Rhizoctonia root and crown rot caused by the fungus RhizoctoniasolaniKühn of the most important diseases of sugar beet, And cause heavy economic losses. Experiments were conducted in plastic pots under field conditions, and laboratory experiments what in the fields and labs of Faculty of Agriculture at the University of Al Furat in Deirezzor during the seasons of 2009 and 2010, to evaluate the effectiveness of some chemical fungicides and bio-control agents(Trichoderma harzianumRifai and Bacillus subtilis Cohn

individually or integrated in controlling root rot and crown in sugar beet caused by Rhizoctoniasolani.

The results showed that all treatments with pesticides and biological agents has significantly reduced the disease incidence and severity of disease, and a significant increase in the average weights and degrees of sweetness of the beets. integration of pesticide Rizolex with fungus 7 harzianumwas superior in artificial inoculation compared to rest of the treatments, where rate and severity of disease in this treatment were 9.2% and 1.11 degrees on the eighth-scale, respectively, while in the control ( infected by pathogen alone) 87.9% and 6.3 degrees on the eighth-scale, respectively. Also, the combined treatment mentioned above achieved a significant increase in the average weights and degrees of sweetness of the beets values amounted to be 722.3 g/root and 17.1%, respectively, while in the infected control was 110.2 g / root and 6.3% for the two traits, respectively. The study showed sensitivity of the fungus R.solaniand

the bio-agents to five concentrations of pesticide tested in vitro in lab. The superiority of the pesticide Rizolex with low concentration to make a 100% inhibition of growth of the mycelium, while inhibition percent of the pesticides Tachigaren and Ridomil ranged between 70 - 86%. T.harzianumand B.subtilis showed a great ability to endure all the concentrations of the pesticide Rizolex. The percent of inhibition ranged from 2.2 -31.1%, and in the average growth of colonies of bacteria between 2.4 and 39.7%, for minimum and maximum concentrations of the pesticide itself, respectively. Whereas the sensitivity of the two bio-agents against the pesticides Ridomil and Tachigaren was high. The percents of inhibition of T.harzianumagainst pesticide Ridomil ranged from 13.3 - 100%, and between 2.4 - 100% of B.subtilis. The percent of inhibition for the bio-agents Tachigaren between 8.8 - 100% for the fungus and between 4.8 - 100% for the bacterium at the minimum and maximum concentrations,respectively.

Key words: sugar beet ; chemical control; bio-control, root rot; crown rot; Rhizoctoniasolani

يعد مرض عفن الجذور والتاج الرايزوكتوني الذي يسببه الفطر Rhizoctonia solani Kühn من أهم الأمراض التي تصيب الشوندر السكري، ويتسبب بخسائر اقتصادية فادحة. لتقييم فاعلية بعض المبيدات الكيميائية وعاملي المكافحة الحيوية الفطر Trichoderma harziant Rifai والبكتريا Bacillus subtilis Cohn بصورة منفردة أو مدمجة في مكافحة المرض، نفذت تجارب مخبرية وفي الأصص البلاستيكية في ظروف الحقل في مخابر وحقول كلية الزراعة في جامعة الفرات بدير الزور في الموسمين 2009 و 2010. أظهرت النتائج أن جميع معاملات المبيدات الكيميائية والعوامل الأحيائية خفضت نسبة وشدة المرض، وزادت في متوسطات أوزان ودرجات حلاوة جذور الشوندر السكري، وقد تفوقت معاملة دمج المبيد Tolclophos-methyl مع الفطر T. harziaruma في ظروف الإعداء الاصطناعي بالفطر الممرض على جميع المعاملات، إذ كانت نسبة وشدة المرض النهائية في هذه المعاملة 2. 9% و 1.11 درجة على التوالي، في حين بلغت في معاملة الشاهد المعدي بالفطر الممرض بمفرده 87.9 %و 6 . 3 درجة على الترتيب، كما حققت معاملة الدمج المذكورة زيادة معنوية في متوسطات أوزان ودرجات حلاوة جذور الشوندر السكري بقيم بلغت 3. 722 غ /جذر و 17.1 % على التوالي، في حين كانت في معاملة الشاهد المعدي