Detailed Explanation of Key Control Techniques for Major Garlic Diseases

Garlic often cannot be controlled promptly and correctly because of differences in disease symptom expression, which leads to severe outbreaks and relatively large losses. Garlic growers are reminded to carry out control of the following diseases:

1. Purple blotch: In the field, the disease mostly begins at the leaf tip or the middle of the flower stalk, and after a few days spreads to the lower part. Initially it appears as slightly sunken small white spots with a slightly purple center; after enlargement, the lesions become yellow-brown, spindle-shaped or oval. When humidity is high, black mold-like material is produced on the diseased area, namely the pathogen's conidiophores and conidia. The lesions mostly have concentric rings and tend to break off from the diseased area. During storage, infected bulbs show the neck becoming dark yellow or reddish-brown soft rot. In the early stage of the 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 with relatively good results.

2. Garlic leaf blight: This is a fungal disease that mainly damages leaves. In the early stage of the disease, the lesions begin between the garlic leaves and gradually develop toward the leaf stem, and spread from the lower part of the plant upward. The lesions are initially pale white round small spots, then gradually expand into gray-brown, oval and irregular shapes. When the disease is severe, it can cause the entire leaves of the garlic plant to wither and die. The diseased parts of garlic affected by leaf blight are often accompanied by black mold-like material, and there are many small black grains on the lesions. After garlic is infected with leaf blight, control measures should be taken promptly to prevent the disease from expanding and spreading. For each mu, 150 g of 40% carbendazim suspension concentrate plus 150 g of potassium dihydrogen phosphate can be used to spray the garlic seedlings evenly 2-3 times, once every about 7 days. Alternatively, 80% zineb at 600-800 times dilution, or 75% chlorothalonil at 600-800 times dilution, or 50% iprodione wettable powder at 1500 times dilution can be sprayed evenly 2-3 times, once every about 7 days.

3. Garlic soft rot: This is a bacterial disease, and low temperature and high humidity favor 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 area becomes yellow-brown and soft-rotted. Generally, the lower leaves are affected first, then it gradually spreads 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 soft rot bacteria, and some pests carry the pathogen internally or externally and directly spread the disease. Therefore, pest control is very important for the control of soft rot. In the early period, attention should be paid to controlling underground pests such as wireworms and mole crickets, and from the seedling stage onward, pests such as striped flea beetles and root maggots should be controlled. Chemical control: before the disease occurs or in the early stage of the disease, 72% agricultural streptomycin at 3000-4000 times dilution, or 47% kasugamycin-copper WP at 750 times dilution, 50% amobam at 1000 times dilution, or new streptomycin at 3000-4000 times dilution can be used, spraying once every 5-7 days, and 2-3 consecutive applications depending on the condition of the disease. The focus should be on lightly diseased plants and the plants around them, and care should be taken to spray the base of the plant stems near the soil surface.