Biology
Leafroll and net necrosis symptoms are caused by a virus. The virus is transmitted by aphids and is also carried in infected tubers. Leaves of plants grown from infected seed pieces show a distinctive upward rolling of the leaf margins and have a brittle or leathery texture. Symptoms first appear at the base of the plant and progress upwards. These plants are generally slightly stunted and yellowish. Plants that are infected by aphid transmission of the virus may show rolling of leaves beginning at the top of the plant, but are seldom stunted. Infected tubers appear normal on the outside, but may display a net necrosis inside the tissues. This is seen as a brownish network of fine lines at the stem end. Net necrosis often develops in storage. The variety 'Russet Burbank' is highly susceptible to net necrosis.
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