Bagged apples suffer severe cracking this year
After the Fuji fruit bags were removed in October, fruit growers in Hebei, Tianjin, Shandong, Shanxi, Henan, Liquan in Shaanxi and other places reported one after another that the apples they produced showed fairly widespread cracking. Why is this?
On October 4, we arrived at the Liujiama orchard in Quyang County, Hebei, to investigate, and found that the bagged apples showed fairly severe fruit cracking after the bags were removed. This orchard uses a dwarfing rootstock high-density planting model, the variety is Red Fuji, and this year is the second year of fruiting. According to the survey, more than 50% of the fruit showed cracking, and on the more severely affected fruit the cracked area of the fruit surface accounted for about 20%. Although cracking does not affect edibility, it seriously affects the appearance of the fruit. On some fruit, because the wounds at the cracked areas became infected by pathogens, red spots began to appear, and further development will form rotting lesions, greatly affecting the sales and storage of the fruit.
In 2015 this orchard had already experienced cracking of bagged fruit, but since the first year's fruit set was relatively small, the main cause analyzed at the time was drought and little rain in June followed by heavy rain later. With this situation occurring again this year, the author believes the cause is not that simple, because we found that quite a few fruits that had been missed when bagging rarely showed cracking, while adjacent bagged fruit on the same tree did crack. It seems that cracking is mainly caused by the adverse effects of the microclimate inside the bag after bagging, and may involve a sharp drop in the uptake of certain elements such as calcium.
The microclimate inside the bag cannot be separated from the larger environment. Based on our observations in recent years, even with bagging, in high-altitude areas such as Luochuan in Shaanxi, Gansu, and the cool southwestern regions, fruit cracking is not severe. This year, no cracking was found in dwarfing rootstock high-density orchards in coastal areas such as Rongcheng, Shandong either. According to exchanges with relevant experts, as early as ten years ago fruit cracking in bagged fruit was also fairly severe in Yuncheng, Shanxi, and the Hengshui area of Hebei, but later, after first putting film bags on the fruit and then paper bags in a two-step procedure, the cracking was noticeably reduced. This year the person in charge of a large several-hundred-mu orchard in Tianjin also reported that with film bags alone the cracking was severe, while without bagging no cracking occurred. Exactly what conditions lead to cracking deserves further in-depth study in the future.