Bagworm is the larval (caterpillar) stage of a native moth that disguises itself by making itself a covering out of the plant material it is feeding on and carrying it around. It is reported to feed on over 100 different trees both conifers and deciduous. Camouflaged, it often goes unmanaged while its populations build up rapidly and become serious pests. On pine trees, its cone-shaped bags are often mistaken of cones.

Some of the more common evergreen host plants include arborvitae (Thuja), fir (Abies), hemlock (Tsuga), juniper (Juniperus), pine (Pinus) and spruce (Picea). Deciduous host plants include black locust (Robinia pseudoacacia), honeylocust (Gleditsia triacanthos), sweetgum (Liquidambar styraciflua) and sycamore (Platanus occidentalis). This season, we are seeing a lot on bald cypress (Taxodium) and white oaks (Quercus spp.) also.

The bags are most noticeable in the winter months. Check you trees now for the cone-like hanging bags made of plant material before the eggs hatch in May. Each overwintering bag contains 500-1000 eggs. You can imagine how quickly a tree can be defoliated if these are allowed to hatch and feed. If your tree is small, you can pick the bags off (they are firmly attached). Use pruners if necessary. DO NOT let the bags fall and lay on the ground! They will hatch. Remove them and destroy them. If your trees are large, arrange now to have them on the schedule for spraying in June.

Although they don’t effectively manage populations, beneficial insects can help. There are parasitoid wasps (not the kind of wasps humans have to fear) you can attract to your landscape by planting flowering plants in the aster (daisy-like) family near your trees.

Rhododendron & Azalea Lacebug

Lacebug damage on rhododendron

Four species of lacebug in the genus Stephanitis cause economic damage to plants in the heath family (Ericaceae) to which azaleas and rhododendrons belong (Mead 1967). Of the four, the most damaging species associated with landscape plants is the azalea lace bug, Stephanitis pyrioides (Cranshaw 2004).

The azalea lace bug is an example of a lace bug which attacks evergreens. The azalea lace bug overwinters in the egg stage. The eggs are partially inserted into the leaf tissues along the midvein and are covered with the resin-like excrement of the female. The nymphs hatch in the spring, usually mid-May. They feed in small groups on the under surface of leaves and molt five times before becoming adults. The adults mate and lay eggs for a second generation by mid to late-July. Often there is a third generation in the late summer and early fall. The andromeda and rhododendron lace bugs have similar life cycles.

Lace bugs actually feed on the underside of leaves with their piercing-sucking mouthparts withdrawing chlorophyll and other plant fluids: but because they kill surrounding cells as they feed, the leaves have the appearance of stippled, bleached, silvery or chlorotic smptoms similar to those caused by mites. When feeding damage becomes severe, the leaves take on a gray blotched appearance or can turn completely brown. As lace bugs feed, they produce brown varnish-like droppings that spot the underside of the leaves. These droppings furthur distinguish lace bug damage from nite damage. When large numbers of lace bugs are present, cast skins can be found attached to the leaves. Even in established landscape plantings, azalea lace bugs can cause considerable damage to foliage if not controlled early in the season when populations are low.

Plants that attract lace bugs should be monitored early in order to determine if an infestation is building. Elimination of the first generation of lace bugs is necessary if visual damage is to be avoided. Existing spotting and yellowing of leaves will not disappear once the lace bugs have been controlled. Most lace bug problems occur in bright, sunny areas. Plant lace bug-susceptible plants in shady areas of the landscape. The azalea and rhododendron lace bugs are rarely a problem when their host plants are in a shaded understory.