White rot is a headache when there’s long time of high temperature and high humidity and it will cause huge loss for the farmers if it cann’t be controlled well.

 

Following pictures are what we received from some farmers this period:

 

1: Symptom of the clusters

White rot mainly harms the clusters, also can harm the young shoots and leaves. If the clusters are infected, firstly will occur on the stalks of the young fruits with light brownish and water-like lesions, and gradually spread to the entire stalks. If occur on the fruits, firstly the fruits’ base will turn brown and soft fot, and quickly the entire fruits will turn brownish and rot, usually white spots could be found on the fruits. In serious cases, the total clusters will rot and the stalks become dry and withered.

2: Occurrence rule

1): The occurrence is highly related with the rainfall. It occurs mainly In June and July, before the harvest. The time and the rate of the rainfall decides the occurring time and level. High temperature, high humidity and the excessive rainfall cause more opportunities of the fungi’s emergence and infection.

2): Because the fungus invade from the wound, so all the conditions that may cause the wound will favor the occurring of White rot, like wind damage, pests and agricultural operations like pruning, pinching and fruit thinning, etc. Especially the wind damage. The White rot usually occurs heavily after the rainstorm.

3): The location of the clusters is also highly related with the diseases’ occurring. According to the survey, the White rot mostly occurs in the clusters that are less than 50cm from the ground. Because they are close to the ground and more easier to be infected by the fungus and the underpart has poor ventilation and high humidity - they are the factors that favor the disease’ occurring.

4): White rot is also likely to occur in the low-lying field with heavy sticky soil and poor drainage conditions.

3: Prevention and control methods

1): Timely removal of pathogens. Grape white rot pathogen stays in the diseased fruits, branches, stems and the leaves. So it’s important to clear the vineyards, take out the diseased plants and burn them. It can decrease next year’s infection rate.

2): Improve the grape trellis’ layout and lift the fruits’ height; Timely cut off the axillary shoots and do pinching.

3): Chemical methods: When the disease is found in the clusters, remove them immediately and spray fungicides with interval of 15 days until 1 month before the harvesting. Following products can be considered: Mancozeb 80% WP, Carbendazim 50% SC, Thiophanate-methyl 50% SC, Difenoconazole 25% EC, Pyraclostrobin 25% EC, Azoxystrobin+Difenoconazole 32.5% SC, Azoxystrobin 25% SC.

4): In 12 hours after the hail and the rainstorm, spray the mentioned fungicides immediately. Mainly spray onto the clusters.