Articles
CHEMICAL THINNING OF APPLE: SOME NEW STRATEGIES AND IMPORTANT REFINEMENTS TO OLD PROCEDURES
However, the discovery that apple thinning can be achieved with photosynthesis inhibitors is an important conceptual breakthrough and other new strategies for selective fruit removal are likely to follow.
This discovery followed logically from results suggesting that post-bloom light conditions and critical demands for photosynthates are important determinants of natural fruit set.
Other chemical thinning agents have been discovered in recent years but none are superior to existing materials.
However, there have been significant developments in product formulation and in other aspects of spray application technology.
Flowable formulations of carbaryl have proven superior in some tests and a paraffinic oil added to carbaryl spray solutions increases thinning activity.
The combination of carbaryl and NAA is a highly effective treatment in many regions and low-volume sprays have proven effective in widely separated tests.
There is an important trend toward more deliberate integration of chemical thinning programs with other cultural techniques aimed at improving fruit quality or controlling tree growth and productivity.
In many instances these techniques involve other plant growth regulators.
Furthermore, good progress is being made toward predicting the need for chemical thinning in any given season.
The .time of harvest may influence flowering and fruit set the next spring; pre- and postbloom light and temperature conditions can influence the time and length of the bloom period as well as fruit set and flower initiation; and the number and distribution of initially set fruits on a tree may be useful for predicting fruit set after the application of chemical thinning sprays.