What causes the bottom leaves of yardlong beans to turn yellow?
Yellowing leaves on yardlong beans are something many vegetable growers who plant yardlong beans encounter often, but there are many different causes of leaf yellowing, and some of these causes, if not treated promptly, can even lead to a total loss of the crop. The following is an introduction to several causes of yellowing leaves in yardlong beans. 1. Symptom presentation. Yellow leaves on yardlong beans are mainly...
Yellowing leaves on yardlong beans are something many vegetable growers who plant yardlong beans encounter often, but there are many different causes of leaf yellowing, and some of these causes, if not treated promptly, can even lead to a total loss of the crop. The following is an introduction to several causes of yellowing leaves in yardlong beans.
1. Symptom presentation
Yellow leaves on yardlong beans mainly take two forms. One is yellowing of the bottom leaves, which drop off easily and gradually spread upward, causing the plant to die. The second is yellowing of the new leaves at the top, often accompanied by flower and pod drop. The third is that the plant does not die, but the leaf blades yellow between the veins.
2. Cause analysis
1. Yardlong bean root rot, commonly known as "red root disease". This is a soil-borne disease; in the early stage the pathogen infects the root system, the plant suffers from poor nutrition, the bottom leaves turn yellow, the plant wilts at noon and recovers in the morning and evening, and finally the plant dies.
2. Lack of trace elements. The leaves at the growing point on top appear yellow-white, caused by iron and zinc deficiency. Yellowing of the new leaves at the top generally occurs after cloudy weather turns suddenly sunny, when root growth is poor, when the weather changes from cold to warm, and when the plant has borne too much fruit earlier on.
3. Poor plant growth. This situation does not cause the plant to die, mainly because poor plant vigor causes the leaves in the middle and lower parts to yellow between the veins, which can easily trigger premature aging of the plant. For example, excessively high greenhouse temperatures, poor root development, root damage, and unscientific fertilizer and water supply can all cause similar situations.
3. Control methods
1. For yardlong bean root rot, chemical root drenching can be used. Optional chemicals: carbendazim + thiram (ethylicin) + hymexazol + copper abietate for root drenching.
2. In bad weather and during the middle and late stages of plant growth, foliar spraying can be used: amino acid foliar fertilizer (chelated with various trace elements such as boron, calcium, magnesium, iron and zinc), which can effectively alleviate the yellow-white color of the new leaves at the top.
3. Enhance plant resistance, cultivate strong roots in the plant, water and fertilize reasonably, and prevent yellowing between the leaf veins that causes premature aging of the leaves.