Nectarine Tree Troubles: Borers and Powdery Mildew

Discovering pin-sized holes, a jelly-like ooze, and a dark gray powdery coating on your nectarine tree's fruit and leaves points to two distinct but simultaneous problems: borer infestation and powdery mildew.

Borers: The Source of Holes and Jelly-Like Sap

The small holes are entry points for borer larvae, likely peach tree borers or shothole borers. The jelly-like substance is sap mixed with frass (insect waste) exuding from the wounds.

Control Measures

• Apply a borer-specific insecticide (such as permethrin or carbaryl) to the trunk and lower branches in spring and summer, following label timing for your region.
• Remove and destroy heavily infested limbs.
• Maintain tree vigor with proper watering and fertilization—healthy trees resist borers better.

Powdery Mildew: The Gray Powder on Leaves and Fruit

The dark gray powder is powdery mildew, a fungal disease that thrives in humid, shady conditions with poor air flow.

Control Measures

• Spray with a fungicide labeled for powdery mildew on stone fruit (sulfur, potassium bicarbonate, or myclobutanil).
• Prune to open the canopy, improving sunlight penetration and air circulation.
• Avoid overhead irrigation; water at the base.
• Clean up fallen leaves and fruit in autumn to reduce overwintering spores.

Integrated Approach

Tackle both issues simultaneously: treat borers with insecticide and mildew with fungicide, while improving cultural conditions. Regular monitoring ensures early detection next season.