Leaf roll in potato (plant on right)Symptoms -- The key symptom is an upward leaf roll (Figure, plant on right). In diagnosing this symptom, it is important to realize that several factors can cause it and they need to be ruled out before deciding on leaf roll. Examples: Rule out black leg by looking for the black slime at the base of the plant stem. Rule out European corn borer damage by looking for an entry hole and frass on the affected stem or branch. Associated with leaf roll is that the leaves are stiff and upon shaking the plant a rattle can be heard. The stiffness and rattle are not observed with the other causes of the leaf roll symptom.

The causal pathogen is the Potato Leaf Roll Virus (PLRV).

The disease appears early in the season when PLRV is carried in the seed piece. Then symptoms appear early and young leaves show an upward roll. Leaves become dry, leathery and thick. They turn brittle and give their distinctive rattle when shaken. Plants may also be severely stunted, erect and light green. Tubers are reduced in size and number. With some varieties, a net necrosis develops inside the tuber. This is very evident during frying of strips (french frying) and slices (chips). The appearance is brown spots radiating outwardly from around the center of the tuber. Net necrosis is an elimination factor that can result in a rejected load for fry and chip processing.

PLRV is also transmitted from infected plants throughout the field by aphids. The aphid of greatest concern is the Green Peach Aphid which can transmit PLRV over and over again (persistent) from plant to plant. Aphid transmission of PLRV occurs later in the season and causes upper leaves to roll, turn pale green and become stiff.

Control measures rely heavily on Certification and aphid control. Roguing is helpful as well.

Potato leaf roll is the major viral problem observed. Refer to descriptions of green peach aphid, its control and its actions as a vector for PLRV under Insects / Vectors / Green Peach Aphid.