Causes of Garlic Leaf Yellowing and How to Prevent and Treat It
Garlic is an indispensable seasoning in the home. Garlic leaves do not have as strong a flavor as garlic cloves, so you do not have to worry about “bad breath” after eating them. Anyone with experience growing garlic has encountered the phenomenon of garlic yellowing. So, what causes the yellowing of garlic leaves? What should be done?
When garlic turns yellow, the main causes are improper fertilizer and water management, soil acidification, and so on. But in fact, garlic yellowing is more likely to be caused by pests and diseases, especially root-knot nematode disease, which has been particularly severe in recent years. Root-knot nematode disease is caused by nematodes infecting crops. Root-knot nematodes harm a wide range of crops. Fruit trees, cucurbits, solanaceous fruits, legumes and other crops are all harmed by nematodes, and garlic is no exception.
According to experts, in recent years, with the adjustment and upgrading of China's agricultural structure, combined with the influence of traditional planting patterns and limited arable land, the multiple cropping index of crops has generally been rather high. In some plots, vegetables, cucurbits and other host plants of nematodes have been grown for a long time, and root-knot nematode disease is severe, leaving a large amount of inoculum in the soil. Garlic is often rotated or intercropped with these host plants, which leads to the occurrence of garlic root-knot nematode disease, and it is especially severe in greenhouses, plastic tunnels and protected cultivation.
According to observations, when the second-stage juveniles of garlic root-knot nematodes harm garlic, they pierce the young parts of the fibrous roots (root tips) with their sharp stylets. Root knots block the roots' absorption of nutrients and water, root growth is hindered, and new roots often fail to grow. The symptoms of diseased plants above ground are not obvious in the early stage of damage, but as the disease develops, they gradually show weakened growth, pale yellow-green leaves, and spreading leaves, similar to the symptoms of water and nutrient deficiency. As the disease develops, the diseased plants gradually turn yellow, wilt, and even wither and die.
It can thus be seen that preventing garlic yellowing cannot be separated from the control of garlic root-knot nematodes. Experts say that controlling root-knot nematodes requires emphasizing prevention over treatment, with prevention as the main approach. Preventive measures can adopt agricultural and physical control methods, while eradicating root-knot nematodes requires combining chemical agents to achieve the best control effect.