Yellow poplar weevils are small black snout beetles (Figure 1) that chew distinctive oval holes in the leaves of yellow poplar, sassafras, and magnolia. The larvae are white legless grubs that feed and develop as miners inside leaves. Injured leaves are unsightly but light feeding does not harm healthy, established trees. These insects are present at low levels every year with occasional population spikes, as seen this year.
There is one generation of the yellow poplar weevil each year. Adults pass winter in leaf litter, emerging on warm days from late April to early May. The weevils attack swelling buds, leaving their distinctive feeding marks (Figures 2 & 3). Holes result from adults puncturing the buds or feeding on the lower surface of leaves.
Females lay their eggs in the midribs on the undersides of leaves. This injury can break the leaf midrib. Newly-hatched larvae move from midribs into leaves where they feed as leaf miners. The mined portions of leaves turn brown and take on a scorched appearance. When ready to pupate, larvae move to an inflated portion of the mine and spin a spherical silk cocoon. The duration of the life cycle varies with environmental conditions.
New adults begin to emerge from leaves during late June; their feeding can be severe. The beetles usually chew only the lower epidermis and mesophyll, leaving the upper epidermis intact. Leaf drop occurs when damaged trees are also under drought stress. By mid-July the adults have disappeared to their hiding places in leaf litter and will remain inactive until spring.
Treatment usually is not necessary. An exception may be if the insects are feeding on more than 10% of the branches of newly established landscape trees. Insecticides labeled for beetle control on shade trees should be effective.
By Lee Townsend, Extension Entomologist