Disease incidence and disease severity of date palm root rot were evaluated on cvs.Barhey, Majdol and Zaghloul during 2021 and 2022 growing seasons in different locations. The highest percentages of disease incidence and disease severity were recorded in nursery located at Beheira governorate, where the lowest were recorded from new orchards in Giza and Qaloubiya governorates during 2021. Isolation trials of the naturally infected date palm root rot yielded four fungal species identified as Fusarium solani, F. moniliforme, F. semitectum and Lasiodiplodia theobromae. Pathogenicity test showed that all isolated fungi were able to induce root rot on date palm seedlings. The highest average disease severity was obtained from the infection with F. solani, followed by F. moniliforme. While, little symptoms showed on the roots inoculated by F. semitectum. Zaghloul cultivar was more susceptible than Barhey and Majdol under artificial inoculation carried out during the two years of the investigation. Efficacy of Biocontrol T34 12% WP (Trichoderma asperellum strain T34), Serenade ASO 1.34% SC, Uniform 39 % SE, Hexaten and Tshgarin 30%SL was evaluated in vitro and under greenhouse conditions for controlling root rot of date palm seedlings. Complete reduction in colony growth of the most frequent fungi was observed due to using Uniform 39 % SE, followed by Hexaten and Tshgarin 30%SL. T34 and Serenade ASO 1.34% SC recorded the lowest efficacy. However, under greenhouse conditions Uniform, Tshgarin and Hexaten gave the highest efficacy for controlling date palm root rot on the two cultivars, Barhey and Zaghloul during the two seasons, while the lowest efficacy was recorded after treatment with T34 and Serenade ASO, respectively. The highest values of total phenol in the three tested date palm cultivars were observed in Barhey cv., while the lowest production were recorded in cv. Zaghloul. The highest values of total phenols was observed after using Uniform and Tshgarin, while the lowest levels of total phenols were recorded by using Serenade ASO. The highest values of polyphenoloxidase activity (PPO) were recorded in cv. Barhey. While the lowest were recorded in cv. Zaghloul. The highest values of PPO were observed after treatment with Tshgarin, while the lowest levels were obtained by using Serenade ASO.

Powdery mildew caused by Erysiphe quercicola is a widespread in several trees in tropical and sub-tropical countries. In November 2020-2021 during an examination of Zizyphus lotus trees growing in Giza, and Qaliobia Governorates, several trees were observed with symptoms of powdery mildew on the leaves, young shoots, and fruits. Powdery mildew mycelium covered large parts of the leaf surfaces, young shoots, and fruits as shown in Fig. 1 (A, B and C). Powdery mildew-infected leaves were collected and kept for further studies. Morphological characteristics of the fungus were studied. The conidiophores bear fragmented, foot cell cylindrical straight or slightly curved at base and non-chained conidia, which are produced singly at the apex of the conidiophores, the primary conidiospores are ellipsoid or ovoid shape, with a rounded apex and truncate base. Meanwhile, mature conidia are mainly dolioform and formed singly. First, mycelial samples were removed from the infected leaves on a microscope slide. The slides were examined under light microscope. Conidiophore produces conidia singly, and consists of a foot-cell, straight or occasionally slightly curved at the base, basal septum at the branching point, followed by one or two cells up to the same length as the foot-cell (Fig. 2). According to the studied morphological characteristics, the causal fungus was identified as E. quercicola (Braun andCook, 2012 andKumar, et al. 2018), the cause of powdery mildew on Zizyphus lotus. DNA was extracted from fungal mass on the infected leaf and amplified for the partial of internal transcribed spacer (ITS) regions with the primers ITS1/ITS4 and sequenced (White et al. 1990). The sequence analysis by BLASTn search of 552 bp (GenBank accession no. MW364272) indicated >99% similarity with Erysiphe quercicola with the accession Nos. MT569439, MT569438, MN394113, KM260690, KM260685, KM260686, KM260688 and KM260687 (Fig. 3). The Zizyphus lotus leaves were inoculated on leaves, all inoculated leaves developed powdery mildew symptoms after 10 days, whereas the control plants remained symptomless. The morphology of the fungus on the inoculated leaves was identical to that initially observed on the infected leaves of Zizyphus lotus. To our knowledge, this is the first record of Erysiphe quercicola in Egypt.