Evaluation of The Effect of Metalaxyl-M and Chlorothalonil Against Downy Mildew in Cucumber and Investigation of Their Residues

Cucumber (Cucumis sativus L.), one of the 30 Cucumis species found worldwide, is the most economically significant. Specified that Pseudoperonospora cubensis causes downy mildew, one of the most destructive foliar diseases affecting cucumbers and other cucurbits. Using a combination of the QuEChERS technique and HPLC, the residue levels and rate of degradation of the commercial fungicide, contained two active components (metalaxyl-M and chlorothalonil), in the cucumber were determined. Additionally, the fungicide's effectiveness was assessed. The experiment was conducted in a greenhouse with a randomized block pattern in the eastern Iraqi city of Ramadi, Anbar Governorate. Cucumbers grown in greenhouses were found to have high amounts of metalaxyl-M and chlorothalonil residues. The fungicide required about 14 days to completely dissipate from the cucumber fruits. The recoveries of chlorothalonil and metalaxyl-M were 90.3 and 86.7%, respectively. The half-lives of metalaxyl-M and chlorothalonil were determined as 0.90 and 0.85, respectively.