What to Do When Cucumbers Get Gray Mold? Symptoms, Damage and Control Methods

Cucumber gray mold is a disease that occurs year-round in protected cucumber cultivation, caused by infection with the fungus Botrytis cinerea of the Deuteromycotina (Fungi Imperfecti). Vegetable growers often call it fruit rot disease or moldy rot disease. In recent years its occurrence has been increasing year by year, and because the fruit is often affected it causes rotting. Now let us take a look at the control methods for cucumber gray mold!

Symptoms of Cucumber Gray Mold

Cucumber gray mold mostly invades starting from spent female flowers. Initially, water-soaked lesions appear at the flower base, and grayish-brown mold gradually grows, causing the floral organs to soften, shrivel and rot, and then gradually spreading to the young fruit. The diseased part of the fruit first turns yellow, later produces white mold that gradually turns light gray, causing the diseased fruit to stop growing, soften, rot and shrivel, and finally rot and drop off. When leaves are infected, the lesions are initially water-soaked, then become irregular light brown spots with distinct edges, and sometimes a small amount of grayish-brown mold grows on the lesions. Under high humidity conditions, the lesions expand rapidly, forming large lesions 15-20 mm in diameter. When stems and vines are infected, the stem rots and the vine breaks, causing the whole plant to rot.

Occurrence Pattern of Cucumber Gray Mold

The pathogen overwinters as mycelium, conidia and sclerotia attached to diseased plant residues or left in the soil, and spreads through wind, rain and farming operations. The fruiting period of cucumbers is the peak period for pathogen infection and disease onset. It is prone to occur under high humidity (relative humidity above 94%), relatively low temperature (18-23°C), insufficient light and weak plant growth. When the temperature exceeds 30°C and the relative humidity is below 90%, the spread stops. Therefore, this disease mostly occurs in greenhouses with low temperature and scant light in winter.

Control Methods for Cucumber Gray Mold

1. Remove diseased plant residues: At the late harvest stage, thoroughly remove diseased plant residues, deep-plow the soil more than 20 cm, turn the diseased residues left on the soil surface into the lower layers, and spray a soil disinfectant plus New High-Fat Film to disinfect the soil, reducing the primary infection sources in the greenhouse. During the seedling stage and before the fruit expands, promptly remove diseased flowers, diseased fruits and diseased leaves, take them out of the greenhouse and bury them deep, reducing the sources of re-infection.

2. Strengthen cultivation management: Strengthen ventilation and air exchange, water moderately, avoid watering on cloudy days, prevent excessive temperature, pay attention to heat preservation, and prevent cold waves from striking. In hot seasons, deep-plow and flood the greenhouse, remove floating matter from the water surface, and bury or burn it in a concentrated manner to keep the greenhouse clean.

3. Regulate temperature and humidity: In planting greenhouses, regulating temperature and humidity can control pathogen infection. Raise the indoor temperature to 31-33°C, start ventilation when it exceeds 33°C, maintain the temperature at 20-25°C in the afternoon, close the vents when it drops to 20°C, and keep the nighttime temperature at 15-17°C.

4. Disinfection and sterilization of the greenhouse. Before planting in seedling greenhouses or production greenhouses, use 5% Procymidone smoke agent at 1 kg per mu to fumigate the closed greenhouse for 24 hours, or spray comprehensively with 40% pyrimethanil suspension concentrate at 1000-1500 times dilution, or 50% iprodione suspension concentrate or wettable powder at 800 times dilution, or 70% thiram at 300 times dilution.

What Are the Main Methods for Controlling Cucumber Gray Mold

Cucumber gray mold is relatively severe during the adult plant stage of cucumbers. It is quite harmful to cucumbers, mainly damaging the fruit, and also damaging leaves and stems. When young fruits are affected, in most cases the residual flowers first develop the disease, which then damages the tip of the fruit and spreads upward. The diseased part of the fruit turns brown and rots, with a dense gray mold layer on the surface. Affected residual flowers or diseased fruits falling onto leaves or stems can cause disease on leaves or stems. So what are the main methods for controlling cucumber gray mold?

To control cucumber gray mold, measures combining control and regulation of the relative temperature in protected cultivation during the fruiting period with timely, reasonable and rotational use of fungicides should be adopted:

(1) Use high-ridge planting, preferably with plastic film mulching; remove excess side branches to ensure good ventilation and light penetration in the field during the fruiting period; in protected cultivation, frequently open the side windows and skylights to reduce temperature and humidity.

(2) 5-7 days before the fruit expansion stage, promptly remove diseased leaves, diseased flowers and diseased fruits to keep the field clean.

(3) At the early stage of disease occurrence, use appropriate fungicides for control. Fumigate with 20% Procymidone smoke agent at 300-400 g per mu each time; with 22% chlorothalonil smoke agent at 200 g per mu each time, ignite at the lowest point of the greenhouse in the evening; spray with 50% Procymidone wettable powder at 1000 times dilution; spray with 50% iprodione wettable powder at 1500 times dilution; spray with 65% procymidone wettable powder at 1500 times dilution; spray with 40% pyrimethanil suspension concentrate at 600-800 times dilution; spray with 70% procymidone wettable powder at 800-**** times dilution; spray with 58% gray mold cleaner wettable powder at 800-**** times dilution; spray with 28% chlorothalonil wettable powder at 800 times dilution. The above fungicides can be used in rotation, alternation or as mixtures, once every 7-10 days, for 2-3 consecutive applications.

How to Control Gray Mold in Winter Melon? Control Methods for Winter Melon Gray Mold

Winter melon gray mold can occur throughout the entire growth process of winter melon and directly affects the growth of winter melon. Next, the editor will introduce in detail the control methods for winter melon gray mold to help everyone grow winter melon better.

Damage Caused by Winter Melon Gray Mold:

The disease can occur throughout the entire growth period, damaging flowers and fruits, and also damaging leaves. When flowers and young fruits are infected, water-soaked spots appear on the petals and stigma, which after expanding fade in color and continue to spread to the flower base and young fruit, showing dark brown water-soaked lesions and growing a grayish-brown mold layer, causing fruit rot. When leaves are infected, relatively large V-shaped lesions appear at the leaf margins, and yellow-brown nearly circular lesions appear on the leaf surface with light yellow edges, and sometimes concentric rings form on the lesions. When humidity is high, grayish-brown mold grows on the diseased parts, namely the pathogen's conidiophores and conidia.

Winter Melon Gray Mold - Pathogen

Botrytis cinerea, a fungus of the Fungi Imperfecti. For the morphological characteristics of the pathogen, transmission routes, disease conditions and pollution-free control methods, refer to cucumber gray mold.

Winter Melon Gray Mold - Control Measures

(1) Select disease-resistant varieties.

(2) Select and keep disease-free seeds, making sure to save seeds from disease-free greenhouses and disease-free plants, and use the frozen filter paper method to test whether the seeds carry the pathogen.

(3) Soak seeds in warm water or fungicide. Soaking seeds in constant-temperature water at 55-60°C for 15 minutes, or soaking seeds in 50% carbendazim wettable powder at 500 times dilution for 20 minutes then rinsing clean before promoting germination, or dressing seeds with 0.3% of 50% carbendazim wettable powder, can all achieve good sterilization results.

(4) Cover with plastic film, adopt water-saving techniques such as drip irrigation, practice crop rotation, and for heavily diseased greenhouses (fields), rotate with non-cucurbit crops.

(5) Fumigation and disinfection. 10 days before planting in greenhouses and plastic tunnels, mix 0.13 kg of sulfur powder and 0.25 kg of sawdust for every 55 cubic meters of space, place the mixture in several spots, ignite it, close the greenhouse tightly, and fumigate for one night.

(6) Strengthen cultivation management. Especially controlling watering from after planting to the fruiting period is very important. For protected cultivation, use ecological control as much as possible, paying particular attention to temperature and humidity management. Use measures such as ventilation to remove moisture and controlled irrigation to reduce humidity inside the greenhouse, reduce leaf surface condensation, and inhibit pathogen germination and invasion. Control the daytime temperature at 28-30°C, nighttime at 15°C, and relative humidity below 90%. In medium-temperature low-humidity greenhouses with an average temperature of 21-25°C, or by controlling greenhouse humidity above 90% for no more than 8 hours, the disease can be reduced.

(7) Use the dust method or smoke method starting at the early stage of disease onset: use a duster to spray 10% carbendazim-mancozeb dust, or 5% black spot prevention dust at 1 kg per mu each time, or apply 45% chlorothalonil smoke agent at 200 g per mu each time, for 3-4 consecutive treatments.

(8) At the early stage of disease onset in greenhouses or open fields, spray 40% flusilazole emulsifiable concentrate at 8000 times dilution, or 50% carbendazim wettable powder at 800 times dilution plus 70% mancozeb wettable powder at 800 times dilution, or 2% Wuyi mycin (BO-10) aqueous solution at 150 times dilution plus 50% carbendazim wettable powder at 600 times dilution, 2% Wuyi mycin (BO-10) aqueous solution at 150 times dilution, 80% carbendazim wettable powder at 600 times dilution, or 75% chlorothalonil wettable powder at 600 times dilution, 50% benomyl wettable powder at 1500 times dilution, 80% captafol wettable powder at 500 times dilution, spraying 60-65 liters of spray solution per mu, once every 7-10 days, for 3-4 consecutive treatments.

(9) Strengthen quarantine to strictly prevent the spread of this disease.