Plant health diagnosis for cut flowers
Case 1 Spots and leaf drop after cold nights - 1
Use Advanced for doses, plans and diagnosis Tap the level next to the microphone. Core gives quick answers and weather checks. Advanced reasons more deeply for spray programs, disease diagnosis and fertilization plans, and can take a minute or two. Auto lets ORTH choose. Every answer in this course used Advanced. For cut flowers Several rose problems cause leaf spots. Keep Advanced on and say which leaves, what the spots look like, where in the plot and after what weather. - 2
Describe the leaves and the nights We described irregular purple to brown spots on young leaves of the new shoots, yellow leaves that drop when touched, after several cold, humid nights. ORTH named rose downy mildew, Peronospora sparsa, as the leading suspicion, still to be confirmed. From 26 October to 5 November the lows had been 7 to 12 °C with rain every day, and at 6 that morning the humidity reached 100%. Inside the greenhouse, the night humidity, the condensation and the hours of leaf wetness decide the risk. - 3
Check before you treat Look under fresh spots early in the morning for fine grey-white or purplish down, before ventilation dries the leaves. Mark and photograph some shoots and recheck after the next humid night. Map where it is: cold edges, leaks, curtains, blocked vents and dense beds point to downy mildew, while a uniform pattern points to cold or spray injury. Rule out Botrytis, black spot, bacterial spots, cold injury and spray injury, review the applications of the last 30 to 60 days and the night climate inside, and send fresh leaves to a lab if there is no down. - 4
What is safe to do now Improve early-morning ventilation and air movement, repair leaks, keep the foliage dry, and bag fallen and diseased leaves after keeping samples for the lab. Work from clean beds towards affected ones and disinfect cutting tools between zones. ORTH advised against a just-in-case fungicide: first confirm the target, then check the current Colombian label for roses, the recent resistance groups, the re-entry rules and the US and EU export protocol. Case 2 If the lab confirms downy mildew - 5
Run the greenhouse dry at night ORTH said to run the greenhouse in active dehumidification, with heat and controlled ventilation together, so the coldest leaves stay above the dew point. Before sunset, keep the curtain open while the crop dries, keep the air moving and stop misting. Close the curtain step by step once the canopy is dry, keeping a controlled exhaust path. At night use the lowest heat that keeps the coldest leaves above the dew point, and when humidity climbs, mix first, then open a small leeward vent while heating. Before dawn, open gradually without dropping curtain water on the crop. Heat alone keeps the water inside, and venting without heat chills the leaves. Climate control stops new infections; leaves that are already infected stay infected. - 6
Know when the climate is working Log air temperature, humidity, dew point, leaf temperature, leaf wetness and the curtain, vents, fans and heating, at canopy height in a central bed and in the coldest spot. The climate works when each heat-and-vent cycle lowers the humidity, the coldest leaf stays above the dew point all night, no leaf wetness is recorded, nothing drips onto the crop, and tagged healthy shoots show no new spots. ORTH gave no fixed heater, curtain or vent setting, because the heater capacity, vent rate and logger data were not on record.
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