Plants often develop a general stunted appearance and bud sheaths may be marked with bluish-green or yellow streaks. This virus is transmitted by aphids. The most effective controls involve roguing and destroying infected plants since the virus persists in these. It is also important to control aphids since they transmit the disease. Insect Problems Aphids.
Aphids occasionally infest iris but cause little injury.
If they are abundant, a spray of malathion or insecticidal soap, which are among the compounds registered for control of this pest in Connecticut, will kill them. Imidacloprid applied as a systemic to be taken up by the roots will also provide season-long control. Consult the label for dosage rates and safety precautions. Iris borer, Macronoctua onusta . The larval stage of this insect is pinkish with a brown head.