BROMIDE RESIDUES IN GREENHOUSE CUCUMBERS AND THE POSSIBILITY OF REDUCING THEM

During the 1979–1980 crop season a survey regarding bromide(Br) residues in cucumber fruits was carried out in 28 plastic greenhouses of Crete, of which seven were not fumigated with methyl bromide(MB) and 21 were fumigated before planting. The average Br content of the former was 7(0–22)μg/g of fresh tissue and that of the latter was 21(5–69)μg/ /g of fresh tissue. A factorial experiment was designed in which hot and cold application of MB at the rate of 75 and 50g/m², leached with 0,50, 100 or 200 1/m² water were tested in an attempt to reduce Br residues without reducing the effectiveness of MB. The experiment was set up in a greenhouse which was never treated with MB and was severely infected with Fusarium oxysporum f.sp. cucurbitae and Meloidogyne sp. The results indicated that, if no leaching was applied, hot application compared to cold and the use of 50g/m² compared to 75g/m² MB reduced Br residues in the soil by 42% and 44% respectively. The reduction of Br residues in the fruits was less pronounced. Leaching was also very effective. If no other treatment was applied, leaching by 50,100 and 2001/m² water reduced Br residues in the soil by 45,81 and 94% and in the fruits of the first harvest by 35,50 and 83% respectively. The Br content of the fruits from the last harvest was approximately 57% lower than that of the first harvest. The effectiveness of MB in disease control was not affected by the method of application or the dosage, but leaching at high levels increased infection by Fusarium wilt which, in the case of 50g/m² MB, resulted in slightly lower yield. Hot application also was less effective in weed control when 50g/m² MB was applied. Meloidogyne sp was controled very effectively by all treatments.