The control of delayed foliation in apples and pears

New chemical rest breaking agents (RBAs) were tested on bearing apple and pear trees in orchards in the Elgin, Villierdorp, Somerset West and Paarl areas during August and September from 1998 to 2003 and rate of budbreak was monitored. In some cases the effect on follow-up sprays on previous year’s treatment sprays  as well as the effect on yields, fruit quality and maturity was also determined.

Dormex*  (hydrogen cyanamide) at 0.5% to 1%, (depending on cultivar and chilling units) mixed with a range of  winter oils at 3 to 4% was found to perform consistently well over successive seasons if sprayed between 7 and 5 weeks before estimated fullbloom, and this product or its registered generic is now recommended.

Yield reductions ascribed to Dormex* are possibly related to premature forcing of buds when sprayed too early, or more likely related to over thinning chemically because of shifts in fullbloom date and concentration of bloom period.  This aspect warrants serious further attention.

A new safer product, Lift^R (thidiazuron/oil), has again performed well except for some fruit deformation which was found to be aggravated by the local oil component, since the mixture containing the imported oil component showed negligible fruit deformation. This aspect warrants further investigation under a contract trial. Other chemicals including generics are continually becoming available, and these should be tested on a contract basis.