How does apple stigma-covering agent affect fruit set rate?

Effect of apple stigma-covering agent on fruit set

Apple flowering and fruit set consume large amounts of stored nutrients in the tree. According to reports, a single apple flower consumes 1 milligram of stored nutrients through respiration during the few days it is open. If flower and fruit thinning are not done in time, and fruit set is not finalized until the fruitlets reach egg size, the nutrients consumed will reach over ten grams to several tens of grams. Moreover, late fruit thinning has little effect on flower bud formation for the following year, and mainly affects fruit size enlargement. For high quality, stable yield and high efficiency, strict flower and fruit thinning is essential and is an important part of apple management.

Although everyone recognizes the importance of flower and fruit thinning, in practice, few implement it in a timely and thorough manner. Most orchards never thin flowers, and even fruit thinning is delayed until just before bagging. Why? The reasons are: (1) Labor is hard to find. At present, young people in rural areas go to cities to work, and those left behind are mostly the elderly, weak, sick, disabled and women. These groups have low educational and technical levels and limited physical strength, and even such laborers are hard to hire. Many orchards provide car transport to and from work in the morning and evening, yet still cannot find enough labor. (2) High labor input and heavy economic burden. At present, for one mu of red Fuji trees in full fruiting stage, flower thinning requires about 10 man-days, each man-day costing 100-120 yuan, plus lunch provided, totaling about 1,200 yuan; if flowers are not thinned and only fruit thinning is done, it still requires 10-12 man-days, at a daily wage of 120 yuan, plus lunch provided, totaling 1,200-1,400 yuan. For not-wealthy fruit growers, this is a heavy burden.

In the 1960s-1970s, we used chemicals for flower and fruit thinning and achieved some results, such as carbaryl, naphthaleneacetic acid, lime sulfur mixture, etc., all of which had certain effects. However, in application, they were greatly affected by weather, tree vigor and variety, with unstable results, and sometimes over-thinning caused yield reduction, so they were not widely promoted in production. To solve the flower thinning problem, based on the characteristic that the king flower and lateral flowers of apple open with a 1-2 day time difference, we designed the following: when the king flower opens on the day and the next day, it generally can be fully pollinated and fertilized, and its fruit set rate is already sufficient for high and abundant yield, so lateral flower fruit set is unnecessary. Therefore, on the day the lateral flowers open, a covering agent is sprayed onto the stigmas, covering the stigmas with a layer of isolating substance, so that germinating pollen cannot enter the pollen tube to complete fertilization, and then the flowers drop off automatically. In this way, each cluster sets 0-2 fruits, and there is room for choosing the final fruit set.

1 Materials and methods

1.1 Test site and materials

Yang Bin orchard in Beiyangjia Village, Suizhong County, Liaoning Province: Wanglin and Red Fuji, trees in full fruiting stage.

Dataishan Fruit Tree Farm in Suizhong County, Liaoning Province: Jonagold and Red Fuji, trees in full fruiting stage.

1.2 Test chemicals and concentrations

The test chemical was Pierre Rivo calcium film produced by Yangling Lvli Bioengineering Co., Ltd., provided by Chairman Han Anke of Sandeli Plant Protection Technology Professional Cooperative in Fufeng County, Shaanxi Province, used at a concentration of 200 times dilution. It was sprayed evenly when the lateral flowers opened. Spraying clean water served as the control.

1.3 Test time

April 20-23, 2017. Yang Bin orchard was sprayed at 10 a.m., and Dataishan Fruit Tree Farm orchard was sprayed at 2 p.m.

2 Results and analysis

Within half a month after spraying, the weather was extremely dry. A field survey was conducted on May 15, and the survey results are shown in Table 1.

From the data in Table 1, it can be seen that obvious effects were achieved on all the tested varieties. First, in Yang Bin orchard, a total of 312 fruit clusters were surveyed on Wanglin trees, and those with 0-2 fruits per cluster accounted for 95.9%; on treated Red Fuji trees, a total of 68 fruit clusters were surveyed, and those with 0-2 fruits per cluster accounted for 86.8%; on control trees, a total of 57 fruit clusters were surveyed, and those with 0-2 fruits per cluster accounted for 47.0%.

Table 1 Effect of Pierre Rivo calcium film on fruit set per cluster

Second, in Dataishan Fruit Tree Farm orchard, a total of 42 fruit clusters were surveyed on Jonagold test trees, and those with 0-2 fruits per cluster accounted for 85.7%; on control trees, a total of 54 fruit clusters were surveyed, and those with 0-2 fruits per cluster accounted for 57.4%; on treated Red Fuji trees, a total of 19 fruit clusters were surveyed, and those with 0-2 fruits per cluster accounted for 68.4%, while on control trees, a total of 23 fruit clusters were surveyed, and those with 0-2 fruits per cluster accounted for 13.0%, a very striking difference.

The above comparison of figures clearly shows that this covering agent indeed has a significant flower-thinning effect and can basically meet the need for labor saving in production.

In addition, the author conducted similar tests in Li Dewen orchard in Shahe Town, Suizhong County, Liaoning Province, Shi Qing orchard, and on Hanfu at the Lazi Mountain test area of the Chinese Academy of Agricultural Sciences Fruit Tree Research Institute. The results showed that each fruit cluster set 3-5 fruits, and the flower-thinning effect was not obvious. The reason may be related to the high self-fruitfulness rate of this variety (about 36%). How to solve this problem remains to be determined by further testing.

3 Summary

As an apple stigma-covering agent, Pierre Rivo calcium film has an obvious flower-thinning effect on several varieties including Wanglin, Red Fuji and Jonagold. It is worth noting that the spraying time must be well controlled in application, spraying when the apple lateral flowers first open, at a concentration of 200 times dilution. To improve the flower-thinning effect on the whole tree, it is recommended to spray promptly on the day the lateral flowers (second batch of flowers) and axillary flower buds (third batch of flowers) open, and the flower-thinning effect will be better.