16 



Advancing Fruit Ripening 



Ethephon (Ethrel^^) can advance the marketing season of most cultivars by 

 increasing red color and advancing ripening. Also, it will accelerate fruit 

 drop if applied alone. Therefore, this compound should either be applied with 

 NAA or on trees that received daminozide earlier in the season. If 

 temperatures are very high following application and the weather remains 

 cloudy, sufficient red color may not develop on treated fruit until ripening is 

 significantly advanced. Because of this potential problem, ethephon should be 

 used on young trees, since light penetration is usually very good and fruit on 

 these trees frequently is too large to have a long storage life. Ripening may 

 advance rapidly on ethephon-treated trees. They should be watched very 

 carefully so that harvesting can be done before excessive fruit drop occurs. 



Growth Control and Flower Bud Formation 



Frequently young trees grow too rapidly thus failing to flower and set 

 fruit. Also, older trees may become too vigorous due to over-fertilization, 

 excessive pruning, or the loss of a crop due to frost. Daminozide, ethephon, 

 or a combination of daminozide and ethephon may be used to retard growth and 

 increase flower bud formation. Treatments should be applied when terminal 

 shoot growth is 4 to 6 inches long. Concentrations of ethephon high enough to 

 reduce terminal growth will also cause excessive fruit thinning. Therefore, 

 ethephon must not be used on trees where cropping is desired the year of 

 application. Young trees should not be sprayed with daminozide and ethephon 

 until they are large enough to bear a crop. 



Water Sprout and Root Sucker Control 



Water sprouts are vigorous, upright shoots arising from any portion of the 

 above-ground part of a tree. They are most prevalent on vigorous trees 

 carrying a light crop. Heavy pruning encourages water sprout growth. It is 

 desirable to restrict growth of these shoots for two reasons: the shade they 

 produce retards red color development, and removing them adds to the pruning 

 costs. Tre-Hold Sprout Inhibitor A112^^ (ethyl ester of NAA) is used to 

 inhibit growth of these shoots. It usually is mixed with interior latex paint 

 and applied to pruning cuts. The paint allows the applicator to see the 

 treated areas, and the increased viscosity of the mixture reduces movement to 

 nontarget areas of the limb. It is important that the inhibitor be applied 

 during the dormant season, because volatilization of the NAA from applications 

 made after the buds start to grow can cause some leaf epinasty and fruit 

 thinning. 



Root sucker control also may be achieved with Tre-Hold. Root suckers 

 should be pruned during the dormant season and the regrowth treated with a Tre- 

 Hold spray. Application should be delayed in the spring until four weeks after 

 bloom to reduce the possibility of fruit thinning. Thorough coverage is 

 essential for success. If there is tall grass or weeds on the orchard floor, 

 it may be useful first to spray under the trees with a contact herbicide such 

 as paraquat. Ten to fourteen days later, follow the herbicide application with 

 the Tre-Hold treatment. Extreme care must be taken to prevent drift since the 

 recommended rate of '''re-Hold is ^00 to 1000 fold higher than the recommended 

 rate of NAA for chemical thinning or drop control. 



