The Latest Technical Guide to Garlic Pest and Disease Control

Garlic is a biennial herbaceous plant of the genus Allium in the Amaryllidaceae family, and is the collective name for plants of the garlic group. It is widely cultivated throughout the country. Because garlic often shows different symptoms of disease, control measures cannot be carried out promptly and correctly, which leads to severe outbreaks and considerable losses. Let us now take a look together at the common pest and disease control techniques for garlic!

Garlic Purple Blotch

[Symptoms]In the field, the disease mostly begins at the leaf tip or the middle of the flower stalk, and within a few days spreads to the lower part. At first, slightly sunken small white spots appear, with a slightly purple center; after enlarging, they become yellow-brown spindle-shaped or oval lesions. When humidity is high, black mold-like material, namely the pathogen's conidiophores and conidia, is produced on the diseased part. The lesions mostly have concentric rings and tend to break off at the diseased part. During storage, the neck of infected bulbs becomes dark yellow or reddish-brown and soft-rotted.

[Control Methods]At the early stage of disease, spray 75% chlorothalonil wettable powder at 500-600 times dilution, or 64% oxadixyl-mancozeb wettable powder at 500 times dilution, 40% dimethomorph wettable powder at 500 times dilution, 58% metalaxyl·mancozeb wettable powder at 500 times dilution, or 50% iprodione wettable powder at 1500 times dilution, once every 7-10 days, for 3-4 consecutive applications, all of which give relatively good results.

Garlic Soft Rot

[Symptoms]Garlic soft rot is a bacterial disease, and low temperature with high humidity favors its occurrence. After garlic is infected, the disease first appears at the leaf margin or midrib, forming yellow-white streaks along the leaf margin or midrib that can run through the entire leaf. When humidity is high, the diseased part becomes yellow-brown and soft-rotted. Generally, the lower leaves are affected first, then it gradually spreads upward to the upper leaves, causing the whole plant to turn yellow and wither or die.

[Pest Control to Prevent Disease]Because pests create wounds on garlic, this favors invasion by the soft rot pathogen, and some pests carry the pathogen inside or on their bodies and directly transmit the disease. Therefore, controlling pests is very important for controlling soft rot. Early on, attention should be paid to controlling underground pests such as wireworms and mole crickets; from the seedling stage onward, pests such as striped flea beetles and root maggots should be controlled.

[Chemical Control]Before disease onset or at the early stage, use 72% agricultural streptomycin at 3000-4000 times dilution, or 47% kasugamycin-copper oxychloride WP at 750 times dilution, 50% amobam at 1000 times dilution, or new zhimesu at 3000-4000 times dilution, spraying once every 5-7 days, for 2-3 consecutive applications depending on disease severity. Focus on lightly diseased plants and the plants around them, and be careful to spray the base of the stems near the soil surface.

Garlic Leaf Blight

[Symptoms]Leaf blight mainly occurs on leaves and flower stalks, and mostly starts from the leaf tip and spreads. The lesions are initially small round white dots, and after enlarging become irregular or oval in shape, appearing grayish-white or grayish-brown, with black mold-like material produced. In severe cases, the diseased leaves wither and die. If the flower stalk is affected, it tends to break at the diseased part, and many small black dots are produced there, making it difficult for garlic to bolt.

[Control Methods]Strengthen field management, plant at a reasonable density, apply comprehensive nitrogen, phosphorus, and potassium fertilizers, add bio-multi-antagonistic bacterial fertilizer, cultivate strong seedlings, drain promptly after rain, and prevent waterlogging in the field. You can spray 75% chlorothalonil or 65% zineb at 500 times dilution, 50% leaf blight powder at 1000 times dilution, or 10% blight-killing powder at 400-500 times dilution.

Garlic Gray Mold

[Symptoms]Gray mold mostly occurs in the later stage of plant growth, starting from the tips of the lower old leaves. The lesions are initially water-soaked, then turn white or light grayish-brown, developing inward from the tip. After enlarging, the lesions become spindle-shaped or oval, and grayish-brown mold-like material is produced on both sides of the lesions. In severe cases, it can spread from the old leaves to all the leaves of the whole plant, causing the leaf sheaths and even the underground bulbs to rot and collapse, then dry up and turn grayish-white, with gray mold and sclerotia visible on the diseased parts.

[Control Methods]The control methods are basically the same as for leaf blight.