Leaf Miners Chrysanthemum and serpentine leaf miners are the common leaf miner species that infest garden mums. Adult females puncture the leaf surface and lay eggs inside the leaf. The eggs hatch into larvae that tunnel between the upper and lower leaf surfaces causing white, twisting mines that disfigure the leaves and reduce marketability. The two-spotted spider mite is the most common mite species that infest garden mums. Spider mites feed on the underside of leaves by sucking plant sap.
Damage appears as tiny yellow speckles on the upper leaf surface.
Severe mite damage can cause leaf drop. Mites are favored by dry warm conditions. The common flower thrip and western flower thrip are the two most common thrips infesting garden mums. Thrips feed on young leaves and flowers using rasping-sucking mouthparts. Feeding on leaves causes a silvery-appearance while damage to flowers causes deformed flower buds, bud abortion, or streaking of petals.