Can I spray phosphonate fungicide on my trees rather than injecting?
Yes, but sprays of phosphonate fungicide should only be applied to apparently healthy trees. Don’t use foliar sprays on affected trees, as they are less effective because of insufficient uptake. Six sprays are recommended between spring and autumn, with no more than about four to six weeks between sprays. Spraying the fungicide can cause a problem. Leaf and fruit burn is likely if phosphonate fungicide is sprayed seven to ten days before or after sprays containing dimethoate, if it is applied with copper hydroxide, or if copper hydroxide residues are present on leaves (buffering the solution to a pH of 7.2 helps to avoid spray burn associated with copper fungicides). A risk may exist with other chemicals as well, depending on the quality of the water used in the spray mixture. As a result, it is often difficult to find at least six ‘safe’ spray points between spring and autumn. An additional problem is that phosphonate fungicide cannot generally be mixed in tanks with endosulfan insect
