What's eating my southern magnolia?

Southern Magnolia's primary pest is magnolia scale, which encrusts branches and fuels sooty mould. Tulip-poplar weevil (magnolia borer) can tunnel into trunks of stressed trees. Deer browse young trees, and scales become severe enough in hot summers to cause dieback. Aphids and thrips cause minor cosmetic leaf spotting.

Large, tan to pink soft scales on young stems; honeydew drips onto lower foliage, feeding sooty mould and covering leaves in black grime. Spray horticultural oil in late summer when crawlers are active. Remove and dispose of heavily infested branches. Apply imidacloprid soil drench in spring for severe infestations on large trees.

Larvae tunnel under bark at the base of trunks and main limbs on stressed trees, causing sap oozing, swollen calluses, and die-back of entire limbs. Keep the tree healthy — avoid wounding, waterlogging, and drought stress. Remove dead or dying wood promptly. Apply preventive permethrin spray to the trunk in late spring when adults are active.

Young trees up to 2 m tall have bark rubbed or stripped by antler-velvet-shedding bucks, and shoots are browsed, stunting early growth. Protect trunks of young trees with spiral guards or rigid mesh guards. Deer repellent spray on foliage and bark can supplement physical protection.

Silvery-brown streaking and small dark faecal specks on large leaves, mainly cosmetic on an established tree. Rarely warrants treatment on mature Southern Magnolias. Maintain vigorous watering during drought to keep the tree resilient; predatory insects provide natural control.