Abstract
The aim of the experiment was to study the causes of the deterioration of the prunus armeniaca L. apricot trees caused by the fungal infection in some orchards of the Al-Qantara, Al-Baydaa / Hosseinieh district/Karbala province in April 2017 and some methods of control. Results of the field survey showed that Prunus armeniaca L. were decline in percentages ranging from 60-70 degrees, The results of isolation showed the presence of Neoscytalidium novaehollandiae, Alternaria porri on potato dextrose Agar (PDA) medium and identified based on its morphological and molecular characterizations and pathogenicity. This identification is the first record of this fungi affecting in Karbala province of Iraq. The pathogenicity test result showed the ability of fungus to cause decline on the seedlings to Prunus armeniaca L. after two months from inoculation time, the result also showed that N. novaehollandiae was more affected with the pathogenicity which differed significantly from the fungus Al. porri, where the lesion length was 0.66 and 0.56 cm respectively and significant difference from the comparison treatment. These fungi showed toxicity for Prunus armeniaca L. through new branches wilt test, and it was found that the tested fungi caused a significant loss in the amount of chlorophyll a (0.37, 0.44 mg−1 wet weight), These results did not differ from chlorophyll b, which increased by increasing concentration. The results of the Gibberellic acid ( GA3) test with four concentrations (100, 200, 300 and 400 mg L−1) showed an active role in the inhibition process, with superiority of 400 mg. L−1 concentration which recorded a 100% rate of tested fungi. Biological control with T. harizanum and T. atroviride results showed superiority on inhibition fungal growth mycelium and high parasitism ability. The results of the effect of GA3 and Biological control with T. harizanum and T. atroviride had an effect in reducing the lesion length where the superiority of GA3 in 400 mg. L−1 concentration, with the total length of the lesion 0.67 cm by comparison and significantly different from the two types of resistant fungi, which recorded a canker length of less 0.41 cm for T. atroviride and 0.47 cm for T.harizanum. with comparison between them and control, which was 1.33 cm long.
