How to treat the blackened tips of green onions (causes and prevention methods of blackened tips of green onions)

The premise of quickly curing the dry tips of onions is to accurately determine the causes of the dry tips. There are many reasons for the dry tips of onions, including physiological dry tips caused by improper water and fertilizer conditions, improper temperature conditions, etc., and pathological dry tips caused by infectious diseases . Generally, the dry tips of onions are caused by the following situations:

1. Dry tip caused by disease

1. Botrytis cinerea

White spots first appear on the leaves, which develop from the tip of the leaf downwards and can extend 2 to 3 cm downwards before drying up. When the humidity is high, a gray mold layer will form on the dead leaves. For prevention and control, spray 44% methylthiocarbamide 600 times + 50% procymidone 1000 times evenly.

2. Root rot

The tips of green onions turn yellow, the root tissue turns black, rots, shrinks and withers, and the root system necrotizes, resulting in dead seedlings and dead plants. The prevention and control method is to spray 30% metalaxyl 1000 times + vancomycin 500 times along the stem side to the root.

3. Onion blight

Bluish-white spots appear on the leaves of green onions, which expand to grayish-white spots, causing the leaves to wither from top to bottom, and a "dry tip" appears in the field. When the humidity is high, sparse white mold grows on the affected plants, and the white mold disappears when the weather is dry.

When the disease occurs seriously, spray 300 times of 58% Lusujing + 1500 times of 80% Dimethomorph + 1500 times of penetration aid Vizhanjing once every 5-7 days for prevention and control.

4. Downy mildew of green onion

The green onion stops growing, the plant height decreases, the leaves become thicker, yellow and bend. In rainy days, a white mold layer may form, the plant turns yellow and withers, and then turns green or dark purple. In severe cases, the diseased plant turns light yellow and withers. The prevention and control methods are similar to those of green onion blight.

Onion blight and downy mildew are easy to occur together, so pay attention to prevention and control in advance.

5. Purple spot disease of green onion

Yellow-white oblong lesions appear in the early stage of the disease, and then quickly expand upward and downward, showing a dark brown spindle shape with a yellow halo on the edge and slight ring patterns on the lesions. You can spray 65% ​​propineb frostbite cyanamide 500 times + 75% chlorpyrifos ...

6. Garlic leaf blight

Onions are infected from the leaf margins and leaf tips, with irregular lesions from small to large, reddish brown to grayish brown, and continuous lesions. You can spray 32.5% benzothiocarb 1500 times + 70% methyl thiophanate 500 times.

7. Onion rust

The green onion will develop oval chlorotic spots, and then a round, slightly raised yellow-brown or reddish-brown blister will appear under the epidermis in the middle of the lesion. When the epidermis of the blister breaks and turns up, orange-yellow powdery summer spores will be released.

When the disease breaks out, the prevention and control method is to use 75% trifloxystrobin tebuconazole 1500 times + 10% flusilazole 1200 times. Use 90 catties of water per mu and spray evenly.

2. Dry tips caused by insect pests

1. Onion thrips danger

When the leaves are damaged, grayish white, irregular spots in the shape of dots or stripes will appear. The insects will drill through the epidermis with their mouthparts and suck the plant juice, causing small white sunken spots to appear on the leaves. The leaves will then turn white and dry up.

When the disease first occurs, you can use 300 times of 6% bifenthrin Tainongzan for prevention and control. When the disease is serious, use 800 times of pyriproxyfen + 1500 times of 20% Mitsui Dimethoate Huiguang Samurai + 300 times of 10% Nifenpyram for thorough prevention and control.

2. Liriomyza scaly

The larvae zigzag through the mesophyll and eat the mesophyll, leaving only the upper and lower epidermis. Circuitous tunnels can be seen on the leaves. In severe cases, the leaves wilt. Control method: Spray the leaves with 1500 times of avermectin + 1500 times of permeability enhancer, cyprodinil.

3. Dry tips caused by physiological diseases

1. Lack of trace elements

Calcium deficiency can easily cause the tips of the heart leaves to turn yellow, hindering their development, while magnesium deficiency can cause the tips of the outer leaves to turn yellow. You can spray with 300 times of amino acid calcium and magnesium water + 1500 times of brassinolide.

2. Continuous drought

Lack of water in plants can easily cause dry tips. Prevention and control should be based on the different water needs of onions at different growth stages, and watering should be done in a timely and appropriate manner.

3. Caused by improper spraying

Phytophthora damage will cause the leaf tips to turn white and dry. If phytophthora damage occurs, spray 1500 times of brassinolide + 300 times of valsartan + 500 times of amino acid liquid fertilizer to eliminate the damage.