What are the key management points for field roses after a flood?
1. Pests and diseases are unlikely to occur, especially downy mildew, the most lethal disease in the growth of cut roses. The reason: the key point of the tall-stem rose cultivation technique is that the nutrient branches are placed on the two sides of the ridge respectively, and the rose stems are about 50 cm above the ridge surface. There are no leaves below the stems, so ventilation and air permeability are very good, which is unfavorable for the growth of pests and diseases and can effectively...
Every year after entering July, different degrees of flooding occur in different parts of the country at different times. From July 7 to 8, heavy rainstorms struck Kunming, Yunnan, causing nearly 10,000 mu of rose seedlings along the shores of Dianchi Lake and in low-lying hilly areas to be soaked in floodwater for more than 24 hours, resulting in direct economic losses of more than 80 million yuan. For this reason, I will use my superficial knowledge of summer management of cut roses to discuss post-flood cut rose production management with flower growers.I. Climate characteristics after flooding
1. The temperature inside the greenhouse is relatively high, and the diurnal temperature difference is large. In central Yunnan, after flooding, inside a plastic greenhouse with a shoulder height of 2 m and a top height of 3.50 m, on a clear midday, the temperature inside the greenhouse is between 28°C and 42°C; inside a plastic greenhouse with a shoulder height of 1.50 m and a top height of 2.50 m, the temperature is between 35°C and 48°C. At night, in greenhouses of the above specifications, the internal temperature is only between 15°C and 17°C.
2. The air humidity inside the greenhouse is relatively high. In plastic greenhouses after the disaster, the relative humidity on clear days is 60%-70%, and at night the humidity is above 80%-90%.
II. Condition of rose seedlings after flooding
1. Mud covers the branches and leaves.
2. Tender branches and young buds wilt or rot on sunny days, and mature or old branches shed their leaves.
3. Petals rot, and the number of rotten buds multiplies.
III. Field management of roses after flooding
1. Drain the standing water in the field as soon as possible, loosen the topsoil in a timely manner, release the toxic gases produced by the roots under anaerobic respiration conditions, reduce root damage, and restore the normal absorption capacity of the root system.
2. Remove damaged flowers, branches and leaves in a timely manner. After flooding, promptly sort out the flowers, branches and leaves that have been crushed, soaked and rotten, or broken by the current, and then spray broad-spectrum fungicides such as carbendazim, chlorothalonil, and metalaxyl.
3. Rinse the sludge off the branches and leaves in a timely manner to restore their photosynthetic capacity. Spray broad-spectrum fungicides such as chlorothalonil, carbendazim, and metalaxyl on the leaves to strive to ensure that the affected branches and leaves do not fall or fall as little as possible.
4. Shade and ventilate to reduce the physiological harm caused to petals by high temperature and high humidity during the day. Cover the greenhouse roof with 30% to 50% shading net, open or roll up the side film of the greenhouse, and promote ventilation and cooling inside the greenhouse. Bring the greenhouse temperature down below 28°C.
5. Prevent downy mildew and gray mold early. After flooding, because the air humidity inside the greenhouse increases and the night temperature drops to 15°C to 18°C, conditions are created for the occurrence of rose gray mold and downy mildew, causing large-scale leaf fall in rose plants and an increase in rotten flowers and rotten buds. The main pesticides for preventing rose downy mildew and gray mold include Kelu, Anke mancozeb, Sumilex, Shijiale, and Ridomil.