The most serious damage occurs when aphids transmit mosaic from infected plants to healthy plants. Foliar applications of malathion or diazinon should adequately control aphids. Di-Syston also is effective against other sucking insects. The potato leafhopper is a frequent pest of dahlias. Potato leafhopper injury results in severely stunted plants that may not bloom.
Early symptoms are pale-colored foliage that curls and browns along the leaf edges.
Of the two, the tarnished plant bug is the more common. Malathion or rotenone will control them, but frequent applications may be necessary if insects are abundant. Treat only if the insects and their damage are present. Mites are tiny, and difficult to see with the unaided eye. Although seldom a problem, mites can be difficult to control once established.