THE EFFECT VENTILATION ON THE RATE OF DOWNY MILDEW INFECTION AND THE RESIDUES OF ELITE FUNGICIDE ON CUCUMBER CULTIVATED IN GREENHOUSE.

Abstract

The study was conducted at the Dujail region, north of Baghdad, during the spring season of 2022, to identify the rate of downy mildew infection and the residues of Elite (fungicide) on the cucumber cultivated in the regular greenhouses compared to the greenhouse with three ventilation openings. The regular greenhouse was sprayed with Elite pesticide, twice; the 1^st treatment sprays was after 7 days of infection onset, and the 2^nd spray was 30 days after the 1^st treatment. The residuals of Elite were, then, estimated. In regards to the 2^nd greenhouse, three ventilation openings were made after the first observation of the disease. The average temperature and a relative humidity (8˚C and 97%, respectively) were reported from the onset of the downy mildew infection on the cucumber. After 2 months, the average of the infection percentage was reported in the regular greenhouse was 1.95%, with a significant difference from the average of percentage the infection in the house of three ventilation openings, which was 1.28%. The average of the Elite residues after three days of spraying was 50, 40 and 28 mg/kg of the cucumber varieties; Mustaqbal, Jamila and Faris, respectively. On the 7^th day of spraying, the average of the Eilit residue was 11mg/kg of the three cucumber varieties. The total production rate of cucumber fruits at the regular greenhouse was 1800 kg, for five times harvest, while it was 3000 kg at the greenhouse with three ventilation openings. The authors concluded that the performance of three ventilation holes into the greenhouse at the time infection onset considered a natural control strategy on the downy mildew disease of cucumber. while in the regular greenhouse sprayed with Elite fungicide, the cucumber crop can be harvested after 3d of spraying, when Elite residues were below the allowable limit (60 mg / kg of cucumber fruits).