Adjuvants for apples effects on russeting

Fruit appearance is of critical importance in apples but fruit rejected for russet make up a significant proportion of the crop each year Nonylphenol ethoxylates have been the standard adjuvants in New Zealand for many years but since their classification as endocrine disruptors alternatives are needed for major export markets Two studies in separate years established the russeting potential in either dilute or concentrate sprays of a range of adjuvants alcohol ethoxylates (Actiwett Chemwet 1000) pinolene polymers (NuFilm17 Sprayfast) polyalkoxylate/aliphatic alcohol blends (Regulaid Spray Aid) an organosilicone/latex polymer blend (Bond Xtra) an organosilicone superspreader (Silwet L77) and an organosilicone blend superspreader (DuWett) Both alcohol ethoxylates significantly increased russet while no other adjuvant had any effects on export packout levels of the russetsensitive varieties Sciros (Pacific Rose) and Sciearly (Pacific Beauty) In the following year concentrate sprays containing DuWett were compared with dilute spray programmes in four commercial orchards in different locations Export packouts of 9098 were achieved The concentrate programmes reduced stemend cheek and total russet in two orchards Fruit quality and the level of export grade fruit (cv Tenroy (Royal Gala) and Braeburn) were not compromised by the use of DuWett adjuvant in concentrate spray programmes