The occurrence of cucumber scab in the greenhouse is widespread, and the damage is serious. It should be strengthened.
First, the symptoms and occurrence conditions of Scab
Seedlings are infected, yellow and white round spots appear on the cotyledons, and the whole leaves dry up after development; stems and stems are immersed in dark green fusiform spots, sag and cracks, when the humidity is high, black mold layer grows, which is the conidia of germs Stems and conidia; stained tendrils turn brown rot; growing spots infected 2 to 3 days rotted into bald piles of inadvertent seedlings; leaves infected at the beginning of dark green near-round spots, after the perforation, the edge of the hole is not neatly brown Sawtooth and periosteal folds; the pale yellow micelles in the early stages of the disease gradually expand into dark green depression spots, and the black mold layer grows on the surface. The diseased spots are sore, and the growth stops and malformation forms.
Scabs are caused by the infection of the fungus A. melitensis and fungi of the subphylum Subgermanium. In addition to harming cucumbers, it also infects zucchini, pumpkins, watermelons, melons and so on. It overwinters with mycelium in diseased or field soils, and the seeds can carry bacteria. Temperature 15 ~ 25 °C, long-term condensation of melon leaves is an important condition of the disease.
Second, control methods
1. Rotation. Rotate with non-cucurbit vegetables.
2. Seed treatment. Soak in 15 to 20 minutes with 55°C hot water.
3. The greenhouse smoked with sulfur powder. In the greenhouse planting or nursery before turning to the ground, 2.5 kg of sulphur per acre mixed with 1 times the amount of dry sawdust, ignited smoke for 24 hours, 7 to 10 days after nursery or colonization, can effectively kill the bacteria.
4. Cultivate strong. Increase phosphorus and potash fertilizers to increase seedling disease resistance.
5. Strengthen the temperature and humidity management. In the management of temperature and humidity, we must pay special attention to the management of humidity. During the production period, it is forbidden to flood irrigation, and the method of humidity increase and humidity reduction and high temperature ventilation should be adopted. The specific approach is: every morning after the dumplings, the humidity in the canopy can reach 90%~100%, and at the same time there is fog. At this time, it is not allowed to ventilate and exhaust. One of the reasons is that the growth period of greenhouse cucumber must be the most suitable high-yielding temperature at 28~33°C every morning. The early air temperature is low, which is not conducive to high cucumber yield. The second reason is that the indoor humidity can be reduced by 2%~3% for every 1°C increase. Therefore, in the morning, when the cold air is released, it is not as good as a warming and humidifying effect. In addition, low-temperature dehumidification due to small temperature difference between indoor and outdoor, moisture can not be discharged. Therefore, the correct way is to open the dumplings every morning, can not immediately release the wind, it should be closed all outlets, so that when it warms up to 33 ~ 35 °C and then suddenly open the air outlet (it must be the top air outlet) for air release dampness. However, when the temperature drops to 30°C, the air outlet must be closed again, and when the temperature exceeds 33°C, the air is released again. Every morning, 2 or 3 times of high-temperature ventilation is performed. In the afternoon, the wind is amplified to reduce the temperature to 25~28°C. In this way, the humidity can be greatly reduced, especially the nighttime humidity, which is conducive to high production, good humidity control, reduced nighttime condensation, and effective control of the occurrence of scab and various diseases.
6. Drug control. Always observe that when a diseased plant is found in the shed (in case the diseased plantlet is removed promptly), the smoke agent should be immediately smoked once a night, and at the same time it can be sprayed with 40% Nova 10 thousand times liquid, or 50% Starlight 600 times, or 50% mancozeb WP 400 to 500 times, or 50% acetaminophen WP 1000 times foliar spray, once every 7 days, pay attention to the alternate use of several drugs can receive better results .
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