How to prevent and control grape gray mold? Master these 4 key points

Gray mold is one of the most common and most serious diseases in grape production. Its pathogen has a wide host range, spreads quickly, and has strong pathogenicity. Once it infects the inflorescence, it can cause the flowers to dry up and drop, resulting in huge yield losses. Below, I will introduce the 4 key points for preventing and controlling grape gray mold.

1. Clean up the greenhouse environment and reduce the primary infection sources

Before planting, clear away residual stubble and dead branches and fallen leaves in the greenhouse; promptly remove diseased leaves, diseased flowers, diseased fruits, and lower yellow leaves and old leaves. After removal, it is best to seal them in plastic bags and take them outside for deep burial or burning. After cleaning up, remember to wash your hands before carrying out other plant management operations, so as to avoid spreading the pathogen through human activity.

2. Strengthen greenhouse facilities and plant cultivation management

(1) Improve cultivation techniques and strengthen field management. After the grapes are planted, adopt double-ridge film and under-film drip irrigation technology to reduce humidity in the greenhouse; watering is best done in the morning on sunny days, and watering on cloudy and rainy days should be avoided; when the midday temperature reaches 25°C-30°C, ventilate to reduce humidity and increase carbon dioxide, bringing the humidity down to about 70%.

(2) Carry out rational close planting according to specific conditions and the morphological characteristics of the variety. Apply base fertilizer mainly composed of decomposed farmyard manure, increase the application of phosphorus and potassium fertilizers, and prevent excessive application of nitrogen fertilizer, which can make the plants too dense and cause excessive vegetative growth, affecting ventilation and light penetration and reducing plant resistance.

3. Improve plant resistance and optimize plant flower and fruit management

(1) Avoid directly carrying out pruning and shoot thinning operations after contact with diseased leaves or diseased fruits, so as to reduce opportunities for the pathogen to invade through wounds. Promptly remove remaining petals and stigmas to prevent the pathogen from harming plant leaves or fruits through remaining petals or stigmas.

(2) Reduce the dosage and concentration of hormones when dipping flowers. Improper use of hormones can cause petals not to drop off. Even if the outside air is relatively dry, the part where the withered petals are trapped between the sepals and the fruit still has very high humidity, and the gray mold pathogen can easily invade and cause damage.

(3) Low temperature and high humidity are the primary conditions for gray mold outbreaks. In ordinary cultivation management, attention should be paid to nourishing roots and protecting leaves, rationally retaining fruits, and cultivating robust plants to enhance stress resistance; also frequently adjust the temperature and humidity in the greenhouse, and lay rice husks, straw, or crop stalks in the operation rows to absorb moisture.

4. Chemical control

Main control agents: pyrimethanil, procymidone, diethofencarb, iprodione, thiram, dimethachlon, pyraclostrobin, boscalid, and fluopyram. Reference control periods:

(1) Late flowering stage: to control early pathogen infection in grape clusters.

(2) Bunching stage: to reduce the number of pathogen infections on stems and pedicels.

(3) Early fruit ripening stage: to prevent grape berries from becoming diseased and drooping.

(4) Three weeks before harvest: to prevent early infection pathogens from spreading further.

(5) Before harvest: mainly to prevent the occurrence of gray mold during transport.