Fruit rot disease caused by Lasiodiplodia theobromae Pat. is one of the most widespread fungal diseases that affects pear worldwide. This work was to verify the efficacy of salicylic acid (SA), lemongrass oil, thyme oil, Imazalil 50% EC and the biofungicide Biocontrol T34 12% WP (Trichoderma asperellum strain T34) against pear fruit rot and their effect on fruit quality parameters. Imazalil and Biocontrol T34 (T. asperellum strain T34) were the best effective treatments, where they completely inhibited the growth of the tested fungus followed by SA. Regarding disease incidence using pre-harvest spray, the highest efficacy was obtained by Imazalil for artificial and natural infection in both 2021 and 2022seasons. All treatments kept fruit quality parameters and had significant effect regarding fruit firmness, total soluble solids (TSS), titratable acidity (TA), total phenolic content (TPC), polyphenoloxidase activity (PPO) and peroxidase activity (PO) for artificial and natural infection in both seasons. The results showed that there was a decrease in pear fruits firmness with increasing the storage period. The decrease in firmness was more noticeable 60 days after storage. The relative high value of pear fruits firmness was obtained due to treatment with each of lemongrass oil and thyme oil with artificial and natural infection. The highest value of total soluble solids % was noted after 60 days storage. In most cases, Imazalil gave the highest TSS values. Pre-harvest treatment with the tested chemicals caused increment TSS values compared with post-harvest treatment. Imazalil gave the highest titratable acidity values. Fruits treated with SA and thyme oil showed the highest values of total phenolic contents in fruits, naturally and/or artificially infected with L. theobromae, respectively in both seasons. PPO and PO activity in pear fruits was significantly increased until 30 days of cold storage at 5°C and 90 % RH during 2021 and 2022 seasons then decreased in all tested fruits treated or untreated of naturally and artificially infected, respectively in both seasons. PPO and PO activity of pear fruits was significantly increased due to post-harvest treatment than pre-harvest spray. Fruits treated by SA, Imazalil and Biocontrol T34 recorded the highest values of both enzymes in the two seasons. Meanwhile, the lowest PPO activity was recorded with control (untreated fruits) in both pre-harvest treatment and post-harvest treatment in both seasons. Control fruits showed the lowest firmness values, TSS, total phenolic contents, PPO, and PO activity in all cases.