Species: Odontopus calceatus (Say) [Coleoptera: CurculionidaeAgromyzidae]
This pest is generally found east of the Mississippi River where its native, preferred hosts, tuliptree (=yellow poplar) and sassafras occur.
This pest attacks tuliptree, sassafras, deciduous and evergreen magnolias.
The adults make bean-shaped, pit-hole feeding spots on several host trees, especially tuliptree, sassafras, southern magnolia and sweetbay magnolia. The larvae make blotch mines in the leaves of these host trees. The adults often cause alarm when the summer generation of adults emerge suddenly in late June. They are very tick-like in form and home owners often express concern about the "flying ticks" that may land on their clothing.
The adult feeding spots are made by chewing away the epidermis and underlying tissues to the epidermis on the other side, a type of pit feeding. The remaining epidermis soon turns brown and may fall out. Holes made on young leaves may appear much larger as the leaf expands.
Description and Life Cycle:
The adult weevils are blackish-brown and about 3/16-inch long. The wing covers and abdomen are much broader than the head and pronotum. The small head with its elongated snout and the stout legs, giving the adult weevil an appearance of a tick.
Adult weevils overwinter in leaf litter until spring temperatures have caused host trees to begin sending out new leaves, usually April and May. The adults feed for a period of time making their characteristic bean shaped spots on leaves. Eventually, the mated females hollow out a small pit in the lower midvein of a leaf. Here the female may deposit one to 15 eggs.
The eggs hatch in a few days into legless, C-shaped grubs that mine a trail to the leaf margin. Near the leaf margin, the larvae enlarge the mine into an irregular blotch. This blotch soon turns brown and it may take up one-fourth of the leaf surface. If a mine is opened, it will appear to be filled with a black, stringy material. These are apparently silk strands with fecal material attached. After three to four weeks of feeding, the mature larvae spin fuzzy, brown, spherical cocoons within the mine.
After another week, the new adults emerge by cutting through the cocoons and leaf surface. They may fly considerable distances and they commonly drop to the ground when disturbed. These new adults feed from late June to late July and do not lay eggs. By mid-August, most of the adults will have found hiding places to overwinter.
As with most leafminers, this pests is easier to manage if the adults are targeted. In most years, natural parasites and predators keep damage below the level requiring action. Every few years, successful reproduction may create considerable adult emergence in June and July which is more of a nuisance than a cause of significant plant damage.
Strategy 1: Cultural Control - Habitat Modifications - Though this pest is called the yellow poplar weevil, it seems to prefer sassafras as a breeding host and sweetbay magnolia as an adult feeding host. Therefore, try to eliminate volunteer sassafras trees surrounding the landscape and use sweetbay magnolia sparingly as an under story planting. Tuliptrees in the landscape appear to be rarely affected.
Strategy 2: Biological Control - Conserve Natural Parasites - This native pest has numerous species of parasitic wasps that attack the larvae and pupae within the leaf mines. These parasites appear to keep this pest under control most years but they may fail every three to five years.
Strategy 3: Chemical Control - Ovipositing Adult Control - For most leafminers, this strategy is usually preferred though complete elimination of the mines is difficult. Apply contact or stomach insecticides as soon as the first adult feeding spots are noticed on host leaves. Since the spring adults feed and move often during April to early June, a second application may be needed.
Strategy 4: Chemical Control - Larval Control - Several systemic insecticides are registered for control of leafmining insects. Most of these systemics are best applied when the eggs have just been laid or while the mines are still greenish in color. Once the mines contain the pupal chambers, it is too late for any pesticides.