If you find holes along the margins of your arborvitae leaves, your plants are probably infested with weevils. These insects are small and black. Their body and wings are covered with metallic green scales and fine short hairs. The larvae are white to pink, with brown heads. They feed on the roots of arborvitae and may attack anytime from june or july to midwinter or the following spring.
Adult weevils emerge from the soil to feed on aboveground plant parts from May to July. The adults usually feed at night and hide in soil and trash during the day. Adult weevils will play dead when disturbed, folding their legs and dropping off plants to the ground. Turn this trait to advantage when fighting this pest. Gently beat the branches of an infested arborvitae and catch the startled insects in a drop cloth spread beneath the shrub. Apply a sticky substance such as Tanglefoot to the trunks of shrub to prevent adults from climbing up and eating the leaves.
Another means of control is to spray shrubs once a week with a solution of pyrethrum mixed with isopropyl alcohol. Combine 1 tablespoon alcohol with 1 pint pyrethrum mix and apply at night, when weevils are active, making sure to cover all leaf surfaces.
|