Making chemical thinning possible under all circumstances
In case of emergency fruit growers can always thin their trees by hand. But rather not. Chemical thinning is much more effective. Applied Plant Research is therefore seeking and testing new products that are effective under all circumstances.
There is no way out for fruit growers: thinning. It is the only way for harvesting good quality apples and pears of the right size. As of old this thinning required a lot of manual labour: workers had to attend all trees to remove excess and weak fruits.
Trees are dropping weak flowers
These days chemical thinning is possible. These products contain growth regulators that cause the tree to drop the weaker fruits. The best time for spraying is four weeks after flowering. At that time it can be seen how many flowers are developing into fruits. Sometimes trees are flowering so abundantly that spraying can better be carried out during flowering. Otherwise it may no longer be possible to remove the excess flowers.
Prevents biannual bearing
Chemical thinning not only has a positive effect on quality grading. It also prevents biannual bearing through the following mechanism. The initiating seeds in the flower buds are producing a hormone that regulates flower bud formation for the following year. The presence of many flowers with seeds results in few flowers in the following year unless the flowers have already been removed before the hormone is formed. This is the case when the flowers are removed within six weeks after flowering. And this is only possible through chemical thinning.
Products are not always working
This is the theory. In practice chemical thinning does not always have the desired result. The existing products are only working at temperatures above 18 degrees centigrade. In addition, certain products require the crop to be dry to avoid scorching spots on the leaves. And this may have a negative effect on fruit growth and fruit quality. And the time of spraying is very sensitive. Spraying too early or too late gives no result.
This means that manual thinning is usually required in addition to chemical thinning. Growers and manufacturers of plant protection products are therefore searching for products that are effective under all conditions. The scientists of Applied Plant Research are testing these new types of products.