Q.White on small nectarine fruit.
Nectarine tree has alot of fruit, however, I notice that some of the fruit has a white substance over them which I can actually wipe off. What can I
do to prevent this and is their something safe that I can spray on the fruit now or is it too late.
The fruit is delicious.
The white powdery stuff on the bark is probably white peach scale. It spreads quickly so control is important. Dormant Oil sprays will help control it as will summer applications of Horticultural Oil. Direct summer sprays to the scale on the bark, minimizing contact with the leaves.
https://www.gardeningknowhow.com/edible/fruits/peach/common-peach-diseases.htm
Peaches are pruned in late winter just before spring growth. Sprays for insects and diseases are usually required several times during the season.
